[Bug] KASAN: slab-use-after-free Read in zswap_decompress

[Bug] KASAN: slab-use-after-free Read in zswap_decompress

[Sam Sun]

Dear developers and maintainers,

We encountered a slab-use-after-free bug while using our modified
syzkaller. Kernel crash log is listed below.

==================================================================
BUG: KASAN: slab-use-after-free in zswap_decompress+0x7d7/0x810 mm/zswap.c:988
Read of size 4 at addr ffff888027874044 by task kswapd0/92

CPU: 1 UID: 0 PID: 92 Comm: kswapd0 Not tainted 6.12.0-09435-g2c22dc1ee3a1 #11
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.16.1-0-g3208b098f51a-prebuilt.qemu.org 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1b0 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xc0/0x5e0 mm/kasan/report.c:489
 kasan_report+0xbd/0xf0 mm/kasan/report.c:602
 zswap_decompress+0x7d7/0x810 mm/zswap.c:988
 zswap_writeback_entry+0x1e9/0x860 mm/zswap.c:1058
 shrink_memcg_cb+0x213/0x360 mm/zswap.c:1163
 __list_lru_walk_one+0x15e/0x490 mm/list_lru.c:301
 list_lru_walk_one+0x3e/0x50 mm/list_lru.c:338
 list_lru_shrink_walk include/linux/list_lru.h:240 [inline]
 zswap_shrinker_scan+0x135/0x220 mm/zswap.c:1197
 do_shrink_slab+0x44e/0x1190 mm/shrinker.c:437
 shrink_slab_memcg mm/shrinker.c:550 [inline]
 shrink_slab+0xb61/0x12a0 mm/shrinker.c:628
 shrink_one+0x4ad/0x7c0 mm/vmscan.c:4836
 shrink_many mm/vmscan.c:4897 [inline]
 lru_gen_shrink_node mm/vmscan.c:4975 [inline]
 shrink_node+0x269a/0x3d60 mm/vmscan.c:5956
 kswapd_shrink_node mm/vmscan.c:6785 [inline]
 balance_pgdat+0xbe5/0x18c0 mm/vmscan.c:6977
 kswapd+0x6ff/0xd60 mm/vmscan.c:7246
 kthread+0x2ca/0x3b0 kernel/kthread.c:389
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>

Allocated by task 1:
 kasan_save_stack+0x24/0x50 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __do_kmalloc_node mm/slub.c:4283 [inline]
 __kmalloc_noprof+0x212/0x530 mm/slub.c:4295
 kmalloc_noprof include/linux/slab.h:905 [inline]
 kzalloc_noprof include/linux/slab.h:1037 [inline]
 __acomp_request_alloc_noprof include/crypto/internal/acompress.h:75 [inline]
 acomp_request_alloc+0x46/0x110 crypto/acompress.c:131
 zswap_cpu_comp_prepare+0x1f4/0x470 mm/zswap.c:840
 cpuhp_invoke_callback+0x26d/0x9d0 kernel/cpu.c:204
 cpuhp_issue_call+0x1c1/0x8d0 kernel/cpu.c:2375
 __cpuhp_state_add_instance_cpuslocked+0x26a/0x3c0 kernel/cpu.c:2437
 __cpuhp_state_add_instance+0xd7/0x2e0 kernel/cpu.c:2458
 cpuhp_state_add_instance include/linux/cpuhotplug.h:386 [inline]
 zswap_pool_create+0x2c3/0x5c0 mm/zswap.c:288
 __zswap_pool_create_fallback mm/zswap.c:356 [inline]
 zswap_setup+0x3a5/0x820 mm/zswap.c:1781
 zswap_init+0x2d/0x40 mm/zswap.c:1817
 do_one_initcall+0x111/0x6d0 init/main.c:1266
 do_initcall_level init/main.c:1328 [inline]
 do_initcalls init/main.c:1344 [inline]
 do_basic_setup init/main.c:1363 [inline]
 kernel_init_freeable+0x5ae/0x8a0 init/main.c:1577
 kernel_init+0x1e/0x2d0 init/main.c:1466
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Freed by task 25:
 kasan_save_stack+0x24/0x50 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:582
 poison_slab_object mm/kasan/common.c:247 [inline]
 __kasan_slab_free+0x54/0x70 mm/kasan/common.c:264
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2338 [inline]
 slab_free mm/slub.c:4598 [inline]
 kfree+0x14e/0x4d0 mm/slub.c:4746
 zswap_cpu_comp_dead+0xe3/0x1c0 mm/zswap.c:874
 cpuhp_invoke_callback+0x564/0x9d0 kernel/cpu.c:216
 __cpuhp_invoke_callback_range+0x104/0x220 kernel/cpu.c:965
 cpuhp_invoke_callback_range kernel/cpu.c:989 [inline]
 cpuhp_down_callbacks kernel/cpu.c:1382 [inline]
 _cpu_down+0x41d/0xef0 kernel/cpu.c:1443
 __cpu_down_maps_locked+0x6f/0x90 kernel/cpu.c:1473
 work_for_cpu_fn+0x55/0xa0 kernel/workqueue.c:6719
 process_one_work+0x9a2/0x1ba0 kernel/workqueue.c:3229
 process_scheduled_works kernel/workqueue.c:3310 [inline]
 worker_thread+0x677/0xe90 kernel/workqueue.c:3391
 kthread+0x2ca/0x3b0 kernel/kthread.c:389
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

The buggy address belongs to the object at ffff888027874000
 which belongs to the cache kmalloc-96 of size 96
The buggy address is located 68 bytes inside of
 freed 96-byte region [ffff888027874000, ffff888027874060)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x27874
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff88801b041280 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000200020 00000001f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask
0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 1, tgid
1 (swapper/0), ts 20389586985, free_ts 18720773637
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x2e7/0x350 mm/page_alloc.c:1556
 prep_new_page mm/page_alloc.c:1564 [inline]
 get_page_from_freelist+0xe4e/0x2b20 mm/page_alloc.c:3474
 __alloc_pages_noprof+0x219/0x21f0 mm/page_alloc.c:4751
 alloc_pages_mpol_noprof+0x2b6/0x600 mm/mempolicy.c:2265
 alloc_slab_page mm/slub.c:2408 [inline]
 allocate_slab mm/slub.c:2574 [inline]
 new_slab+0x2d5/0x420 mm/slub.c:2627
 ___slab_alloc+0xbb7/0x1850 mm/slub.c:3815
 __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3905
 __slab_alloc_node mm/slub.c:3980 [inline]
 slab_alloc_node mm/slub.c:4141 [inline]
 __do_kmalloc_node mm/slub.c:4282 [inline]
 __kmalloc_noprof+0x2ac/0x530 mm/slub.c:4295
 kmalloc_noprof include/linux/slab.h:905 [inline]
 kzalloc_noprof include/linux/slab.h:1037 [inline]
 __acomp_request_alloc_noprof include/crypto/internal/acompress.h:75 [inline]
 acomp_request_alloc+0x46/0x110 crypto/acompress.c:131
 zswap_cpu_comp_prepare+0x1f4/0x470 mm/zswap.c:840
 cpuhp_invoke_callback+0x26d/0x9d0 kernel/cpu.c:204
 cpuhp_issue_call+0x1c1/0x8d0 kernel/cpu.c:2375
 __cpuhp_state_add_instance_cpuslocked+0x26a/0x3c0 kernel/cpu.c:2437
 __cpuhp_state_add_instance+0xd7/0x2e0 kernel/cpu.c:2458
 cpuhp_state_add_instance include/linux/cpuhotplug.h:386 [inline]
 zswap_pool_create+0x2c3/0x5c0 mm/zswap.c:288
 __zswap_pool_create_fallback mm/zswap.c:356 [inline]
 zswap_setup+0x3a5/0x820 mm/zswap.c:1781
page last free pid 54 tgid 54 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1127 [inline]
 free_unref_page+0x714/0x10c0 mm/page_alloc.c:2657
 vfree+0x17e/0x890 mm/vmalloc.c:3382
 delayed_vfree_work+0x57/0x70 mm/vmalloc.c:3303
 process_one_work+0x9a2/0x1ba0 kernel/workqueue.c:3229
 process_scheduled_works kernel/workqueue.c:3310 [inline]
 worker_thread+0x677/0xe90 kernel/workqueue.c:3391
 kthread+0x2ca/0x3b0 kernel/kthread.c:389
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Memory state around the buggy address:
 ffff888027873f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888027873f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888027874000: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
                                           ^
 ffff888027874080: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
 ffff888027874100: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
==================================================================
We also find a similar bug report in function zswap_store(), listed as below:

==================================================================
BUG: KASAN: slab-use-after-free in zswap_compress mm/zswap.c:925 [inline]
BUG: KASAN: slab-use-after-free in zswap_store_page mm/zswap.c:1426 [inline]
BUG: KASAN: slab-use-after-free in zswap_store+0x2307/0x25e0 mm/zswap.c:1533
Read of size 4 at addr ffff8880219f6b44 by task kswapd0/88

CPU: 1 UID: 0 PID: 88 Comm: kswapd0 Tainted: G     U
6.12.0-09435-g2c22dc1ee3a1 #11
Tainted: [U]=USER
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.16.1-0-g3208b098f51a-prebuilt.qemu.org 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1b0 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xc0/0x5e0 mm/kasan/report.c:489
 kasan_report+0xbd/0xf0 mm/kasan/report.c:602
 zswap_compress mm/zswap.c:925 [inline]
 zswap_store_page mm/zswap.c:1426 [inline]
 zswap_store+0x2307/0x25e0 mm/zswap.c:1533
 swap_writepage+0x3a8/0xe50 mm/page_io.c:279
 pageout+0x3b9/0xa90 mm/vmscan.c:689
 shrink_folio_list+0x2988/0x4340 mm/vmscan.c:1367
 evict_folios+0x72b/0x1a10 mm/vmscan.c:4593
 try_to_shrink_lruvec+0x62b/0xa60 mm/vmscan.c:4789
 shrink_one+0x417/0x7c0 mm/vmscan.c:4834
 shrink_many mm/vmscan.c:4897 [inline]
 lru_gen_shrink_node mm/vmscan.c:4975 [inline]
 shrink_node+0x269a/0x3d60 mm/vmscan.c:5956
 kswapd_shrink_node mm/vmscan.c:6785 [inline]
 balance_pgdat+0xbe5/0x18c0 mm/vmscan.c:6977
 kswapd+0x6ff/0xd60 mm/vmscan.c:7246
 kthread+0x2ca/0x3b0 kernel/kthread.c:389
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>

Allocated by task 1:
 kasan_save_stack+0x24/0x50 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __do_kmalloc_node mm/slub.c:4283 [inline]
 __kmalloc_noprof+0x212/0x530 mm/slub.c:4295
 kmalloc_noprof include/linux/slab.h:905 [inline]
 kzalloc_noprof include/linux/slab.h:1037 [inline]
 __acomp_request_alloc_noprof include/crypto/internal/acompress.h:75 [inline]
 acomp_request_alloc+0x46/0x110 crypto/acompress.c:131
 zswap_cpu_comp_prepare+0x1f4/0x470 mm/zswap.c:840
 cpuhp_invoke_callback+0x26d/0x9d0 kernel/cpu.c:204
 cpuhp_issue_call+0x1c1/0x8d0 kernel/cpu.c:2375
 __cpuhp_state_add_instance_cpuslocked+0x26a/0x3c0 kernel/cpu.c:2437
 __cpuhp_state_add_instance+0xd7/0x2e0 kernel/cpu.c:2458
 cpuhp_state_add_instance include/linux/cpuhotplug.h:386 [inline]
 zswap_pool_create+0x2c3/0x5c0 mm/zswap.c:288
 __zswap_pool_create_fallback mm/zswap.c:356 [inline]
 zswap_setup+0x3a5/0x820 mm/zswap.c:1781
 zswap_init+0x2d/0x40 mm/zswap.c:1817
 do_one_initcall+0x111/0x6d0 init/main.c:1266
 do_initcall_level init/main.c:1328 [inline]
 do_initcalls init/main.c:1344 [inline]
 do_basic_setup init/main.c:1363 [inline]
 kernel_init_freeable+0x5ae/0x8a0 init/main.c:1577
 kernel_init+0x1e/0x2d0 init/main.c:1466
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Freed by task 901:
 kasan_save_stack+0x24/0x50 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:582
 poison_slab_object mm/kasan/common.c:247 [inline]
 __kasan_slab_free+0x54/0x70 mm/kasan/common.c:264
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2338 [inline]
 slab_free mm/slub.c:4598 [inline]
 kfree+0x14e/0x4d0 mm/slub.c:4746
 zswap_cpu_comp_dead+0xe3/0x1c0 mm/zswap.c:874
 cpuhp_invoke_callback+0x564/0x9d0 kernel/cpu.c:216
 __cpuhp_invoke_callback_range+0x104/0x220 kernel/cpu.c:965
 cpuhp_invoke_callback_range kernel/cpu.c:989 [inline]
 cpuhp_down_callbacks kernel/cpu.c:1382 [inline]
 _cpu_down+0x41d/0xef0 kernel/cpu.c:1443
 __cpu_down_maps_locked+0x6f/0x90 kernel/cpu.c:1473
 work_for_cpu_fn+0x55/0xa0 kernel/workqueue.c:6719
 process_one_work+0x9a2/0x1ba0 kernel/workqueue.c:3229
 process_scheduled_works kernel/workqueue.c:3310 [inline]
 worker_thread+0x677/0xe90 kernel/workqueue.c:3391
 kthread+0x2ca/0x3b0 kernel/kthread.c:389
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

The buggy address belongs to the object at ffff8880219f6b00
 which belongs to the cache kmalloc-96 of size 96
The buggy address is located 68 bytes inside of
 freed 96-byte region [ffff8880219f6b00, ffff8880219f6b60)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x219f6
anon flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff88801b041280 ffffea0000887d00 dead000000000005
raw: 0000000000000000 0000000000200020 00000001f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask
0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 1, tgid
1 (swapper/0), ts 15792736110, free_ts 14433067061
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x2e7/0x350 mm/page_alloc.c:1556
 prep_new_page mm/page_alloc.c:1564 [inline]
 get_page_from_freelist+0xe4e/0x2b20 mm/page_alloc.c:3474
 __alloc_pages_noprof+0x219/0x21f0 mm/page_alloc.c:4751
 alloc_pages_mpol_noprof+0x2b6/0x600 mm/mempolicy.c:2265
 alloc_slab_page mm/slub.c:2408 [inline]
 allocate_slab mm/slub.c:2574 [inline]
 new_slab+0x2d5/0x420 mm/slub.c:2627
 ___slab_alloc+0xbb7/0x1850 mm/slub.c:3815
 __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3905
 __slab_alloc_node mm/slub.c:3980 [inline]
 slab_alloc_node mm/slub.c:4141 [inline]
 __kmalloc_cache_noprof+0x280/0x410 mm/slub.c:4309
 kmalloc_noprof include/linux/slab.h:901 [inline]
 kzalloc_noprof include/linux/slab.h:1037 [inline]
 usb_hub_create_port_device+0xbb/0xde0 drivers/usb/core/port.c:743
 hub_configure drivers/usb/core/hub.c:1710 [inline]
 hub_probe+0x1ceb/0x2fc0 drivers/usb/core/hub.c:1965
 usb_probe_interface+0x314/0x9f0 drivers/usb/core/driver.c:399
 call_driver_probe drivers/base/dd.c:579 [inline]
 really_probe+0x252/0xa90 drivers/base/dd.c:658
 __driver_probe_device+0x1df/0x450 drivers/base/dd.c:800
 driver_probe_device+0x4c/0x1a0 drivers/base/dd.c:830
 __device_attach_driver+0x1db/0x2f0 drivers/base/dd.c:958
 bus_for_each_drv+0x14c/0x1d0 drivers/base/bus.c:459
page last free pid 25 tgid 25 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1127 [inline]
 free_unref_page+0x714/0x10c0 mm/page_alloc.c:2657
 vfree+0x17e/0x890 mm/vmalloc.c:3382
 delayed_vfree_work+0x57/0x70 mm/vmalloc.c:3303
 process_one_work+0x9a2/0x1ba0 kernel/workqueue.c:3229
 process_scheduled_works kernel/workqueue.c:3310 [inline]
 worker_thread+0x677/0xe90 kernel/workqueue.c:3391
 kthread+0x2ca/0x3b0 kernel/kthread.c:389
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Memory state around the buggy address:
 ffff8880219f6a00: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
 ffff8880219f6a80: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
>ffff8880219f6b00: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
                                           ^
 ffff8880219f6b80: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
 ffff8880219f6c00: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
==================================================================
If you have any questions, please contact us.

Best Regards,
Yue

Re: [Bug] KASAN: slab-use-after-free Read in zswap_decompress

[Yosry Ahmed]

On Tue, Dec 17, 2024 at 2:52 AM Sam Sun <samsun1006219@gmail.com> wrote:
>
> Dear developers and maintainers,
>
> We encountered a slab-use-after-free bug while using our modified
> syzkaller. Kernel crash log is listed below.


Thanks for reporting this!

This seems to be the problem that Johannes pointed out in:
https://lore.kernel.org/lkml/20241113213007.GB1564047@cmpxchg.org/.

Would you be able to check if the following diff fixes the problem?

diff --git a/mm/zswap.c b/mm/zswap.c
index 0030ce8fecfc5..089d70dee3246 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -875,6 +875,21 @@ static int zswap_cpu_comp_dead(unsigned int cpu,
struct hlist_node *node)
        return 0;
 }

+static void acomp_ctx_get_cpu(struct crypto_acomp_ctx *acomp_ctx)
+{
+       /*
+        * Prevent CPU hotplug from freeing this CPU's acomp_ctx until
+        * acomp_ctx_put_cpu().
+        */
+       cpus_read_lock();
+       return raw_cpu_ptr
+}
+
+static void acomp_ctx_put_cpu(void)
+{
+       cpus_read_unlock();
+}
+
 static bool zswap_compress(struct folio *folio, struct zswap_entry *entry)
 {
        struct crypto_acomp_ctx *acomp_ctx;
@@ -887,8 +902,7 @@ static bool zswap_compress(struct folio *folio,
struct zswap_entry *entry)
        gfp_t gfp;
        u8 *dst;

-       acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
-
+       acomp_ctx = acomp_ctx_get_cpu(entry->pool->acomp_ctx);
        mutex_lock(&acomp_ctx->mutex);

        dst = acomp_ctx->buffer;
@@ -944,6 +958,7 @@ static bool zswap_compress(struct folio *folio,
struct zswap_entry *entry)
                zswap_reject_alloc_fail++;

        mutex_unlock(&acomp_ctx->mutex);
+       acomp_ctx_put_cpu();
        return comp_ret == 0 && alloc_ret == 0;
 }

@@ -954,7 +969,7 @@ static void zswap_decompress(struct zswap_entry
*entry, struct folio *folio)
        struct crypto_acomp_ctx *acomp_ctx;
        u8 *src;

-       acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
+       acomp_ctx = acompx_ctx_get_cpu(entry->pool->acomp_ctx);
        mutex_lock(&acomp_ctx->mutex);

        src = zpool_map_handle(zpool, entry->handle, ZPOOL_MM_RO);
@@ -984,6 +999,7 @@ static void zswap_decompress(struct zswap_entry
*entry, struct folio *folio)

        if (src != acomp_ctx->buffer)
                zpool_unmap_handle(zpool, entry->handle);
+       acomp_ctx_put_cpu();
 }

 /*********************************


>
>
> ==================================================================
> BUG: KASAN: slab-use-after-free in zswap_decompress+0x7d7/0x810 mm/zswap.c:988
> Read of size 4 at addr ffff888027874044 by task kswapd0/92
>
> CPU: 1 UID: 0 PID: 92 Comm: kswapd0 Not tainted 6.12.0-09435-g2c22dc1ee3a1 #11
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> rel-1.16.1-0-g3208b098f51a-prebuilt.qemu.org 04/01/2014
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:94 [inline]
>  dump_stack_lvl+0x116/0x1b0 lib/dump_stack.c:120
>  print_address_description mm/kasan/report.c:378 [inline]
>  print_report+0xc0/0x5e0 mm/kasan/report.c:489
>  kasan_report+0xbd/0xf0 mm/kasan/report.c:602
>  zswap_decompress+0x7d7/0x810 mm/zswap.c:988
>  zswap_writeback_entry+0x1e9/0x860 mm/zswap.c:1058
>  shrink_memcg_cb+0x213/0x360 mm/zswap.c:1163
>  __list_lru_walk_one+0x15e/0x490 mm/list_lru.c:301
>  list_lru_walk_one+0x3e/0x50 mm/list_lru.c:338
>  list_lru_shrink_walk include/linux/list_lru.h:240 [inline]
>  zswap_shrinker_scan+0x135/0x220 mm/zswap.c:1197
>  do_shrink_slab+0x44e/0x1190 mm/shrinker.c:437
>  shrink_slab_memcg mm/shrinker.c:550 [inline]
>  shrink_slab+0xb61/0x12a0 mm/shrinker.c:628
>  shrink_one+0x4ad/0x7c0 mm/vmscan.c:4836
>  shrink_many mm/vmscan.c:4897 [inline]
>  lru_gen_shrink_node mm/vmscan.c:4975 [inline]
>  shrink_node+0x269a/0x3d60 mm/vmscan.c:5956
>  kswapd_shrink_node mm/vmscan.c:6785 [inline]
>  balance_pgdat+0xbe5/0x18c0 mm/vmscan.c:6977
>  kswapd+0x6ff/0xd60 mm/vmscan.c:7246
>  kthread+0x2ca/0x3b0 kernel/kthread.c:389
>  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
>  </TASK>
>
> Allocated by task 1:
>  kasan_save_stack+0x24/0x50 mm/kasan/common.c:47
>  kasan_save_track+0x14/0x30 mm/kasan/common.c:68
>  poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
>  __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
>  kasan_kmalloc include/linux/kasan.h:260 [inline]
>  __do_kmalloc_node mm/slub.c:4283 [inline]
>  __kmalloc_noprof+0x212/0x530 mm/slub.c:4295
>  kmalloc_noprof include/linux/slab.h:905 [inline]
>  kzalloc_noprof include/linux/slab.h:1037 [inline]
>  __acomp_request_alloc_noprof include/crypto/internal/acompress.h:75 [inline]
>  acomp_request_alloc+0x46/0x110 crypto/acompress.c:131
>  zswap_cpu_comp_prepare+0x1f4/0x470 mm/zswap.c:840
>  cpuhp_invoke_callback+0x26d/0x9d0 kernel/cpu.c:204
>  cpuhp_issue_call+0x1c1/0x8d0 kernel/cpu.c:2375
>  __cpuhp_state_add_instance_cpuslocked+0x26a/0x3c0 kernel/cpu.c:2437
>  __cpuhp_state_add_instance+0xd7/0x2e0 kernel/cpu.c:2458
>  cpuhp_state_add_instance include/linux/cpuhotplug.h:386 [inline]
>  zswap_pool_create+0x2c3/0x5c0 mm/zswap.c:288
>  __zswap_pool_create_fallback mm/zswap.c:356 [inline]
>  zswap_setup+0x3a5/0x820 mm/zswap.c:1781
>  zswap_init+0x2d/0x40 mm/zswap.c:1817
>  do_one_initcall+0x111/0x6d0 init/main.c:1266
>  do_initcall_level init/main.c:1328 [inline]
>  do_initcalls init/main.c:1344 [inline]
>  do_basic_setup init/main.c:1363 [inline]
>  kernel_init_freeable+0x5ae/0x8a0 init/main.c:1577
>  kernel_init+0x1e/0x2d0 init/main.c:1466
>  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
>
> Freed by task 25:
>  kasan_save_stack+0x24/0x50 mm/kasan/common.c:47
>  kasan_save_track+0x14/0x30 mm/kasan/common.c:68
>  kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:582
>  poison_slab_object mm/kasan/common.c:247 [inline]
>  __kasan_slab_free+0x54/0x70 mm/kasan/common.c:264
>  kasan_slab_free include/linux/kasan.h:233 [inline]
>  slab_free_hook mm/slub.c:2338 [inline]
>  slab_free mm/slub.c:4598 [inline]
>  kfree+0x14e/0x4d0 mm/slub.c:4746
>  zswap_cpu_comp_dead+0xe3/0x1c0 mm/zswap.c:874
>  cpuhp_invoke_callback+0x564/0x9d0 kernel/cpu.c:216
>  __cpuhp_invoke_callback_range+0x104/0x220 kernel/cpu.c:965
>  cpuhp_invoke_callback_range kernel/cpu.c:989 [inline]
>  cpuhp_down_callbacks kernel/cpu.c:1382 [inline]
>  _cpu_down+0x41d/0xef0 kernel/cpu.c:1443
>  __cpu_down_maps_locked+0x6f/0x90 kernel/cpu.c:1473
>  work_for_cpu_fn+0x55/0xa0 kernel/workqueue.c:6719
>  process_one_work+0x9a2/0x1ba0 kernel/workqueue.c:3229
>  process_scheduled_works kernel/workqueue.c:3310 [inline]
>  worker_thread+0x677/0xe90 kernel/workqueue.c:3391
>  kthread+0x2ca/0x3b0 kernel/kthread.c:389
>  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
>
> The buggy address belongs to the object at ffff888027874000
>  which belongs to the cache kmalloc-96 of size 96
> The buggy address is located 68 bytes inside of
>  freed 96-byte region [ffff888027874000, ffff888027874060)
>
> The buggy address belongs to the physical page:
> page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x27874
> flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
> page_type: f5(slab)
> raw: 00fff00000000000 ffff88801b041280 dead000000000100 dead000000000122
> raw: 0000000000000000 0000000000200020 00000001f5000000 0000000000000000
> page dumped because: kasan: bad access detected
> page_owner tracks the page as allocated
> page last allocated via order 0, migratetype Unmovable, gfp_mask
> 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 1, tgid
> 1 (swapper/0), ts 20389586985, free_ts 18720773637
>  set_page_owner include/linux/page_owner.h:32 [inline]
>  post_alloc_hook+0x2e7/0x350 mm/page_alloc.c:1556
>  prep_new_page mm/page_alloc.c:1564 [inline]
>  get_page_from_freelist+0xe4e/0x2b20 mm/page_alloc.c:3474
>  __alloc_pages_noprof+0x219/0x21f0 mm/page_alloc.c:4751
>  alloc_pages_mpol_noprof+0x2b6/0x600 mm/mempolicy.c:2265
>  alloc_slab_page mm/slub.c:2408 [inline]
>  allocate_slab mm/slub.c:2574 [inline]
>  new_slab+0x2d5/0x420 mm/slub.c:2627
>  ___slab_alloc+0xbb7/0x1850 mm/slub.c:3815
>  __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3905
>  __slab_alloc_node mm/slub.c:3980 [inline]
>  slab_alloc_node mm/slub.c:4141 [inline]
>  __do_kmalloc_node mm/slub.c:4282 [inline]
>  __kmalloc_noprof+0x2ac/0x530 mm/slub.c:4295
>  kmalloc_noprof include/linux/slab.h:905 [inline]
>  kzalloc_noprof include/linux/slab.h:1037 [inline]
>  __acomp_request_alloc_noprof include/crypto/internal/acompress.h:75 [inline]
>  acomp_request_alloc+0x46/0x110 crypto/acompress.c:131
>  zswap_cpu_comp_prepare+0x1f4/0x470 mm/zswap.c:840
>  cpuhp_invoke_callback+0x26d/0x9d0 kernel/cpu.c:204
>  cpuhp_issue_call+0x1c1/0x8d0 kernel/cpu.c:2375
>  __cpuhp_state_add_instance_cpuslocked+0x26a/0x3c0 kernel/cpu.c:2437
>  __cpuhp_state_add_instance+0xd7/0x2e0 kernel/cpu.c:2458
>  cpuhp_state_add_instance include/linux/cpuhotplug.h:386 [inline]
>  zswap_pool_create+0x2c3/0x5c0 mm/zswap.c:288
>  __zswap_pool_create_fallback mm/zswap.c:356 [inline]
>  zswap_setup+0x3a5/0x820 mm/zswap.c:1781
> page last free pid 54 tgid 54 stack trace:
>  reset_page_owner include/linux/page_owner.h:25 [inline]
>  free_pages_prepare mm/page_alloc.c:1127 [inline]
>  free_unref_page+0x714/0x10c0 mm/page_alloc.c:2657
>  vfree+0x17e/0x890 mm/vmalloc.c:3382
>  delayed_vfree_work+0x57/0x70 mm/vmalloc.c:3303
>  process_one_work+0x9a2/0x1ba0 kernel/workqueue.c:3229
>  process_scheduled_works kernel/workqueue.c:3310 [inline]
>  worker_thread+0x677/0xe90 kernel/workqueue.c:3391
>  kthread+0x2ca/0x3b0 kernel/kthread.c:389
>  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
>
> Memory state around the buggy address:
>  ffff888027873f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>  ffff888027873f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> >ffff888027874000: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>                                            ^
>  ffff888027874080: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
>  ffff888027874100: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
> ==================================================================
> We also find a similar bug report in function zswap_store(), listed as below:
>
> ==================================================================
> BUG: KASAN: slab-use-after-free in zswap_compress mm/zswap.c:925 [inline]
> BUG: KASAN: slab-use-after-free in zswap_store_page mm/zswap.c:1426 [inline]
> BUG: KASAN: slab-use-after-free in zswap_store+0x2307/0x25e0 mm/zswap.c:1533
> Read of size 4 at addr ffff8880219f6b44 by task kswapd0/88
>
> CPU: 1 UID: 0 PID: 88 Comm: kswapd0 Tainted: G     U
> 6.12.0-09435-g2c22dc1ee3a1 #11
> Tainted: [U]=USER
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> rel-1.16.1-0-g3208b098f51a-prebuilt.qemu.org 04/01/2014
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:94 [inline]
>  dump_stack_lvl+0x116/0x1b0 lib/dump_stack.c:120
>  print_address_description mm/kasan/report.c:378 [inline]
>  print_report+0xc0/0x5e0 mm/kasan/report.c:489
>  kasan_report+0xbd/0xf0 mm/kasan/report.c:602
>  zswap_compress mm/zswap.c:925 [inline]
>  zswap_store_page mm/zswap.c:1426 [inline]
>  zswap_store+0x2307/0x25e0 mm/zswap.c:1533
>  swap_writepage+0x3a8/0xe50 mm/page_io.c:279
>  pageout+0x3b9/0xa90 mm/vmscan.c:689
>  shrink_folio_list+0x2988/0x4340 mm/vmscan.c:1367
>  evict_folios+0x72b/0x1a10 mm/vmscan.c:4593
>  try_to_shrink_lruvec+0x62b/0xa60 mm/vmscan.c:4789
>  shrink_one+0x417/0x7c0 mm/vmscan.c:4834
>  shrink_many mm/vmscan.c:4897 [inline]
>  lru_gen_shrink_node mm/vmscan.c:4975 [inline]
>  shrink_node+0x269a/0x3d60 mm/vmscan.c:5956
>  kswapd_shrink_node mm/vmscan.c:6785 [inline]
>  balance_pgdat+0xbe5/0x18c0 mm/vmscan.c:6977
>  kswapd+0x6ff/0xd60 mm/vmscan.c:7246
>  kthread+0x2ca/0x3b0 kernel/kthread.c:389
>  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
>  </TASK>
>
> Allocated by task 1:
>  kasan_save_stack+0x24/0x50 mm/kasan/common.c:47
>  kasan_save_track+0x14/0x30 mm/kasan/common.c:68
>  poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
>  __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
>  kasan_kmalloc include/linux/kasan.h:260 [inline]
>  __do_kmalloc_node mm/slub.c:4283 [inline]
>  __kmalloc_noprof+0x212/0x530 mm/slub.c:4295
>  kmalloc_noprof include/linux/slab.h:905 [inline]
>  kzalloc_noprof include/linux/slab.h:1037 [inline]
>  __acomp_request_alloc_noprof include/crypto/internal/acompress.h:75 [inline]
>  acomp_request_alloc+0x46/0x110 crypto/acompress.c:131
>  zswap_cpu_comp_prepare+0x1f4/0x470 mm/zswap.c:840
>  cpuhp_invoke_callback+0x26d/0x9d0 kernel/cpu.c:204
>  cpuhp_issue_call+0x1c1/0x8d0 kernel/cpu.c:2375
>  __cpuhp_state_add_instance_cpuslocked+0x26a/0x3c0 kernel/cpu.c:2437
>  __cpuhp_state_add_instance+0xd7/0x2e0 kernel/cpu.c:2458
>  cpuhp_state_add_instance include/linux/cpuhotplug.h:386 [inline]
>  zswap_pool_create+0x2c3/0x5c0 mm/zswap.c:288
>  __zswap_pool_create_fallback mm/zswap.c:356 [inline]
>  zswap_setup+0x3a5/0x820 mm/zswap.c:1781
>  zswap_init+0x2d/0x40 mm/zswap.c:1817
>  do_one_initcall+0x111/0x6d0 init/main.c:1266
>  do_initcall_level init/main.c:1328 [inline]
>  do_initcalls init/main.c:1344 [inline]
>  do_basic_setup init/main.c:1363 [inline]
>  kernel_init_freeable+0x5ae/0x8a0 init/main.c:1577
>  kernel_init+0x1e/0x2d0 init/main.c:1466
>  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
>
> Freed by task 901:
>  kasan_save_stack+0x24/0x50 mm/kasan/common.c:47
>  kasan_save_track+0x14/0x30 mm/kasan/common.c:68
>  kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:582
>  poison_slab_object mm/kasan/common.c:247 [inline]
>  __kasan_slab_free+0x54/0x70 mm/kasan/common.c:264
>  kasan_slab_free include/linux/kasan.h:233 [inline]
>  slab_free_hook mm/slub.c:2338 [inline]
>  slab_free mm/slub.c:4598 [inline]
>  kfree+0x14e/0x4d0 mm/slub.c:4746
>  zswap_cpu_comp_dead+0xe3/0x1c0 mm/zswap.c:874
>  cpuhp_invoke_callback+0x564/0x9d0 kernel/cpu.c:216
>  __cpuhp_invoke_callback_range+0x104/0x220 kernel/cpu.c:965
>  cpuhp_invoke_callback_range kernel/cpu.c:989 [inline]
>  cpuhp_down_callbacks kernel/cpu.c:1382 [inline]
>  _cpu_down+0x41d/0xef0 kernel/cpu.c:1443
>  __cpu_down_maps_locked+0x6f/0x90 kernel/cpu.c:1473
>  work_for_cpu_fn+0x55/0xa0 kernel/workqueue.c:6719
>  process_one_work+0x9a2/0x1ba0 kernel/workqueue.c:3229
>  process_scheduled_works kernel/workqueue.c:3310 [inline]
>  worker_thread+0x677/0xe90 kernel/workqueue.c:3391
>  kthread+0x2ca/0x3b0 kernel/kthread.c:389
>  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
>
> The buggy address belongs to the object at ffff8880219f6b00
>  which belongs to the cache kmalloc-96 of size 96
> The buggy address is located 68 bytes inside of
>  freed 96-byte region [ffff8880219f6b00, ffff8880219f6b60)
>
> The buggy address belongs to the physical page:
> page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x219f6
> anon flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
> page_type: f5(slab)
> raw: 00fff00000000000 ffff88801b041280 ffffea0000887d00 dead000000000005
> raw: 0000000000000000 0000000000200020 00000001f5000000 0000000000000000
> page dumped because: kasan: bad access detected
> page_owner tracks the page as allocated
> page last allocated via order 0, migratetype Unmovable, gfp_mask
> 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 1, tgid
> 1 (swapper/0), ts 15792736110, free_ts 14433067061
>  set_page_owner include/linux/page_owner.h:32 [inline]
>  post_alloc_hook+0x2e7/0x350 mm/page_alloc.c:1556
>  prep_new_page mm/page_alloc.c:1564 [inline]
>  get_page_from_freelist+0xe4e/0x2b20 mm/page_alloc.c:3474
>  __alloc_pages_noprof+0x219/0x21f0 mm/page_alloc.c:4751
>  alloc_pages_mpol_noprof+0x2b6/0x600 mm/mempolicy.c:2265
>  alloc_slab_page mm/slub.c:2408 [inline]
>  allocate_slab mm/slub.c:2574 [inline]
>  new_slab+0x2d5/0x420 mm/slub.c:2627
>  ___slab_alloc+0xbb7/0x1850 mm/slub.c:3815
>  __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3905
>  __slab_alloc_node mm/slub.c:3980 [inline]
>  slab_alloc_node mm/slub.c:4141 [inline]
>  __kmalloc_cache_noprof+0x280/0x410 mm/slub.c:4309
>  kmalloc_noprof include/linux/slab.h:901 [inline]
>  kzalloc_noprof include/linux/slab.h:1037 [inline]
>  usb_hub_create_port_device+0xbb/0xde0 drivers/usb/core/port.c:743
>  hub_configure drivers/usb/core/hub.c:1710 [inline]
>  hub_probe+0x1ceb/0x2fc0 drivers/usb/core/hub.c:1965
>  usb_probe_interface+0x314/0x9f0 drivers/usb/core/driver.c:399
>  call_driver_probe drivers/base/dd.c:579 [inline]
>  really_probe+0x252/0xa90 drivers/base/dd.c:658
>  __driver_probe_device+0x1df/0x450 drivers/base/dd.c:800
>  driver_probe_device+0x4c/0x1a0 drivers/base/dd.c:830
>  __device_attach_driver+0x1db/0x2f0 drivers/base/dd.c:958
>  bus_for_each_drv+0x14c/0x1d0 drivers/base/bus.c:459
> page last free pid 25 tgid 25 stack trace:
>  reset_page_owner include/linux/page_owner.h:25 [inline]
>  free_pages_prepare mm/page_alloc.c:1127 [inline]
>  free_unref_page+0x714/0x10c0 mm/page_alloc.c:2657
>  vfree+0x17e/0x890 mm/vmalloc.c:3382
>  delayed_vfree_work+0x57/0x70 mm/vmalloc.c:3303
>  process_one_work+0x9a2/0x1ba0 kernel/workqueue.c:3229
>  process_scheduled_works kernel/workqueue.c:3310 [inline]
>  worker_thread+0x677/0xe90 kernel/workqueue.c:3391
>  kthread+0x2ca/0x3b0 kernel/kthread.c:389
>  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
>
> Memory state around the buggy address:
>  ffff8880219f6a00: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
>  ffff8880219f6a80: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
> >ffff8880219f6b00: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>                                            ^
>  ffff8880219f6b80: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
>  ffff8880219f6c00: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> ==================================================================
> If you have any questions, please contact us.
>
> Best Regards,
> Yue

Re: [Bug] KASAN: slab-use-after-free Read in zswap_decompress

[Yosry Ahmed]

[-- Attachment #1: Type: text/plain, Size: 19735 bytes --]

On Tue, Dec 17, 2024 at 8:30 AM Yosry Ahmed <yosryahmed@google.com> wrote:
>
> On Tue, Dec 17, 2024 at 2:52 AM Sam Sun <samsun1006219@gmail.com> wrote:
> >
> > Dear developers and maintainers,
> >
> > We encountered a slab-use-after-free bug while using our modified
> > syzkaller. Kernel crash log is listed below.
>
>
> Thanks for reporting this!
>
> This seems to be the problem that Johannes pointed out in:
> https://lore.kernel.org/lkml/20241113213007.GB1564047@cmpxchg.org/.
>
> Would you be able to check if the following diff fixes the problem?

I sent a poached semi-staged git diff, apologies. Please try the
proper patch attached instead.



>
> diff --git a/mm/zswap.c b/mm/zswap.c
> index 0030ce8fecfc5..089d70dee3246 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -875,6 +875,21 @@ static int zswap_cpu_comp_dead(unsigned int cpu,
> struct hlist_node *node)
>         return 0;
>  }
>
> +static void acomp_ctx_get_cpu(struct crypto_acomp_ctx *acomp_ctx)
> +{
> +       /*
> +        * Prevent CPU hotplug from freeing this CPU's acomp_ctx until
> +        * acomp_ctx_put_cpu().
> +        */
> +       cpus_read_lock();
> +       return raw_cpu_ptr
> +}
> +
> +static void acomp_ctx_put_cpu(void)
> +{
> +       cpus_read_unlock();
> +}
> +
>  static bool zswap_compress(struct folio *folio, struct zswap_entry *entry)
>  {
>         struct crypto_acomp_ctx *acomp_ctx;
> @@ -887,8 +902,7 @@ static bool zswap_compress(struct folio *folio,
> struct zswap_entry *entry)
>         gfp_t gfp;
>         u8 *dst;
>
> -       acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
> -
> +       acomp_ctx = acomp_ctx_get_cpu(entry->pool->acomp_ctx);
>         mutex_lock(&acomp_ctx->mutex);
>
>         dst = acomp_ctx->buffer;
> @@ -944,6 +958,7 @@ static bool zswap_compress(struct folio *folio,
> struct zswap_entry *entry)
>                 zswap_reject_alloc_fail++;
>
>         mutex_unlock(&acomp_ctx->mutex);
> +       acomp_ctx_put_cpu();
>         return comp_ret == 0 && alloc_ret == 0;
>  }
>
> @@ -954,7 +969,7 @@ static void zswap_decompress(struct zswap_entry
> *entry, struct folio *folio)
>         struct crypto_acomp_ctx *acomp_ctx;
>         u8 *src;
>
> -       acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
> +       acomp_ctx = acompx_ctx_get_cpu(entry->pool->acomp_ctx);
>         mutex_lock(&acomp_ctx->mutex);
>
>         src = zpool_map_handle(zpool, entry->handle, ZPOOL_MM_RO);
> @@ -984,6 +999,7 @@ static void zswap_decompress(struct zswap_entry
> *entry, struct folio *folio)
>
>         if (src != acomp_ctx->buffer)
>                 zpool_unmap_handle(zpool, entry->handle);
> +       acomp_ctx_put_cpu();
>  }
>
>  /*********************************
>
>
> >
> >
> > ==================================================================
> > BUG: KASAN: slab-use-after-free in zswap_decompress+0x7d7/0x810 mm/zswap.c:988
> > Read of size 4 at addr ffff888027874044 by task kswapd0/92
> >
> > CPU: 1 UID: 0 PID: 92 Comm: kswapd0 Not tainted 6.12.0-09435-g2c22dc1ee3a1 #11
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> > rel-1.16.1-0-g3208b098f51a-prebuilt.qemu.org 04/01/2014
> > Call Trace:
> >  <TASK>
> >  __dump_stack lib/dump_stack.c:94 [inline]
> >  dump_stack_lvl+0x116/0x1b0 lib/dump_stack.c:120
> >  print_address_description mm/kasan/report.c:378 [inline]
> >  print_report+0xc0/0x5e0 mm/kasan/report.c:489
> >  kasan_report+0xbd/0xf0 mm/kasan/report.c:602
> >  zswap_decompress+0x7d7/0x810 mm/zswap.c:988
> >  zswap_writeback_entry+0x1e9/0x860 mm/zswap.c:1058
> >  shrink_memcg_cb+0x213/0x360 mm/zswap.c:1163
> >  __list_lru_walk_one+0x15e/0x490 mm/list_lru.c:301
> >  list_lru_walk_one+0x3e/0x50 mm/list_lru.c:338
> >  list_lru_shrink_walk include/linux/list_lru.h:240 [inline]
> >  zswap_shrinker_scan+0x135/0x220 mm/zswap.c:1197
> >  do_shrink_slab+0x44e/0x1190 mm/shrinker.c:437
> >  shrink_slab_memcg mm/shrinker.c:550 [inline]
> >  shrink_slab+0xb61/0x12a0 mm/shrinker.c:628
> >  shrink_one+0x4ad/0x7c0 mm/vmscan.c:4836
> >  shrink_many mm/vmscan.c:4897 [inline]
> >  lru_gen_shrink_node mm/vmscan.c:4975 [inline]
> >  shrink_node+0x269a/0x3d60 mm/vmscan.c:5956
> >  kswapd_shrink_node mm/vmscan.c:6785 [inline]
> >  balance_pgdat+0xbe5/0x18c0 mm/vmscan.c:6977
> >  kswapd+0x6ff/0xd60 mm/vmscan.c:7246
> >  kthread+0x2ca/0x3b0 kernel/kthread.c:389
> >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> >  </TASK>
> >
> > Allocated by task 1:
> >  kasan_save_stack+0x24/0x50 mm/kasan/common.c:47
> >  kasan_save_track+0x14/0x30 mm/kasan/common.c:68
> >  poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
> >  __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
> >  kasan_kmalloc include/linux/kasan.h:260 [inline]
> >  __do_kmalloc_node mm/slub.c:4283 [inline]
> >  __kmalloc_noprof+0x212/0x530 mm/slub.c:4295
> >  kmalloc_noprof include/linux/slab.h:905 [inline]
> >  kzalloc_noprof include/linux/slab.h:1037 [inline]
> >  __acomp_request_alloc_noprof include/crypto/internal/acompress.h:75 [inline]
> >  acomp_request_alloc+0x46/0x110 crypto/acompress.c:131
> >  zswap_cpu_comp_prepare+0x1f4/0x470 mm/zswap.c:840
> >  cpuhp_invoke_callback+0x26d/0x9d0 kernel/cpu.c:204
> >  cpuhp_issue_call+0x1c1/0x8d0 kernel/cpu.c:2375
> >  __cpuhp_state_add_instance_cpuslocked+0x26a/0x3c0 kernel/cpu.c:2437
> >  __cpuhp_state_add_instance+0xd7/0x2e0 kernel/cpu.c:2458
> >  cpuhp_state_add_instance include/linux/cpuhotplug.h:386 [inline]
> >  zswap_pool_create+0x2c3/0x5c0 mm/zswap.c:288
> >  __zswap_pool_create_fallback mm/zswap.c:356 [inline]
> >  zswap_setup+0x3a5/0x820 mm/zswap.c:1781
> >  zswap_init+0x2d/0x40 mm/zswap.c:1817
> >  do_one_initcall+0x111/0x6d0 init/main.c:1266
> >  do_initcall_level init/main.c:1328 [inline]
> >  do_initcalls init/main.c:1344 [inline]
> >  do_basic_setup init/main.c:1363 [inline]
> >  kernel_init_freeable+0x5ae/0x8a0 init/main.c:1577
> >  kernel_init+0x1e/0x2d0 init/main.c:1466
> >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> >
> > Freed by task 25:
> >  kasan_save_stack+0x24/0x50 mm/kasan/common.c:47
> >  kasan_save_track+0x14/0x30 mm/kasan/common.c:68
> >  kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:582
> >  poison_slab_object mm/kasan/common.c:247 [inline]
> >  __kasan_slab_free+0x54/0x70 mm/kasan/common.c:264
> >  kasan_slab_free include/linux/kasan.h:233 [inline]
> >  slab_free_hook mm/slub.c:2338 [inline]
> >  slab_free mm/slub.c:4598 [inline]
> >  kfree+0x14e/0x4d0 mm/slub.c:4746
> >  zswap_cpu_comp_dead+0xe3/0x1c0 mm/zswap.c:874
> >  cpuhp_invoke_callback+0x564/0x9d0 kernel/cpu.c:216
> >  __cpuhp_invoke_callback_range+0x104/0x220 kernel/cpu.c:965
> >  cpuhp_invoke_callback_range kernel/cpu.c:989 [inline]
> >  cpuhp_down_callbacks kernel/cpu.c:1382 [inline]
> >  _cpu_down+0x41d/0xef0 kernel/cpu.c:1443
> >  __cpu_down_maps_locked+0x6f/0x90 kernel/cpu.c:1473
> >  work_for_cpu_fn+0x55/0xa0 kernel/workqueue.c:6719
> >  process_one_work+0x9a2/0x1ba0 kernel/workqueue.c:3229
> >  process_scheduled_works kernel/workqueue.c:3310 [inline]
> >  worker_thread+0x677/0xe90 kernel/workqueue.c:3391
> >  kthread+0x2ca/0x3b0 kernel/kthread.c:389
> >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> >
> > The buggy address belongs to the object at ffff888027874000
> >  which belongs to the cache kmalloc-96 of size 96
> > The buggy address is located 68 bytes inside of
> >  freed 96-byte region [ffff888027874000, ffff888027874060)
> >
> > The buggy address belongs to the physical page:
> > page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x27874
> > flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
> > page_type: f5(slab)
> > raw: 00fff00000000000 ffff88801b041280 dead000000000100 dead000000000122
> > raw: 0000000000000000 0000000000200020 00000001f5000000 0000000000000000
> > page dumped because: kasan: bad access detected
> > page_owner tracks the page as allocated
> > page last allocated via order 0, migratetype Unmovable, gfp_mask
> > 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 1, tgid
> > 1 (swapper/0), ts 20389586985, free_ts 18720773637
> >  set_page_owner include/linux/page_owner.h:32 [inline]
> >  post_alloc_hook+0x2e7/0x350 mm/page_alloc.c:1556
> >  prep_new_page mm/page_alloc.c:1564 [inline]
> >  get_page_from_freelist+0xe4e/0x2b20 mm/page_alloc.c:3474
> >  __alloc_pages_noprof+0x219/0x21f0 mm/page_alloc.c:4751
> >  alloc_pages_mpol_noprof+0x2b6/0x600 mm/mempolicy.c:2265
> >  alloc_slab_page mm/slub.c:2408 [inline]
> >  allocate_slab mm/slub.c:2574 [inline]
> >  new_slab+0x2d5/0x420 mm/slub.c:2627
> >  ___slab_alloc+0xbb7/0x1850 mm/slub.c:3815
> >  __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3905
> >  __slab_alloc_node mm/slub.c:3980 [inline]
> >  slab_alloc_node mm/slub.c:4141 [inline]
> >  __do_kmalloc_node mm/slub.c:4282 [inline]
> >  __kmalloc_noprof+0x2ac/0x530 mm/slub.c:4295
> >  kmalloc_noprof include/linux/slab.h:905 [inline]
> >  kzalloc_noprof include/linux/slab.h:1037 [inline]
> >  __acomp_request_alloc_noprof include/crypto/internal/acompress.h:75 [inline]
> >  acomp_request_alloc+0x46/0x110 crypto/acompress.c:131
> >  zswap_cpu_comp_prepare+0x1f4/0x470 mm/zswap.c:840
> >  cpuhp_invoke_callback+0x26d/0x9d0 kernel/cpu.c:204
> >  cpuhp_issue_call+0x1c1/0x8d0 kernel/cpu.c:2375
> >  __cpuhp_state_add_instance_cpuslocked+0x26a/0x3c0 kernel/cpu.c:2437
> >  __cpuhp_state_add_instance+0xd7/0x2e0 kernel/cpu.c:2458
> >  cpuhp_state_add_instance include/linux/cpuhotplug.h:386 [inline]
> >  zswap_pool_create+0x2c3/0x5c0 mm/zswap.c:288
> >  __zswap_pool_create_fallback mm/zswap.c:356 [inline]
> >  zswap_setup+0x3a5/0x820 mm/zswap.c:1781
> > page last free pid 54 tgid 54 stack trace:
> >  reset_page_owner include/linux/page_owner.h:25 [inline]
> >  free_pages_prepare mm/page_alloc.c:1127 [inline]
> >  free_unref_page+0x714/0x10c0 mm/page_alloc.c:2657
> >  vfree+0x17e/0x890 mm/vmalloc.c:3382
> >  delayed_vfree_work+0x57/0x70 mm/vmalloc.c:3303
> >  process_one_work+0x9a2/0x1ba0 kernel/workqueue.c:3229
> >  process_scheduled_works kernel/workqueue.c:3310 [inline]
> >  worker_thread+0x677/0xe90 kernel/workqueue.c:3391
> >  kthread+0x2ca/0x3b0 kernel/kthread.c:389
> >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> >
> > Memory state around the buggy address:
> >  ffff888027873f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> >  ffff888027873f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> > >ffff888027874000: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> >                                            ^
> >  ffff888027874080: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
> >  ffff888027874100: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
> > ==================================================================
> > We also find a similar bug report in function zswap_store(), listed as below:
> >
> > ==================================================================
> > BUG: KASAN: slab-use-after-free in zswap_compress mm/zswap.c:925 [inline]
> > BUG: KASAN: slab-use-after-free in zswap_store_page mm/zswap.c:1426 [inline]
> > BUG: KASAN: slab-use-after-free in zswap_store+0x2307/0x25e0 mm/zswap.c:1533
> > Read of size 4 at addr ffff8880219f6b44 by task kswapd0/88
> >
> > CPU: 1 UID: 0 PID: 88 Comm: kswapd0 Tainted: G     U
> > 6.12.0-09435-g2c22dc1ee3a1 #11
> > Tainted: [U]=USER
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> > rel-1.16.1-0-g3208b098f51a-prebuilt.qemu.org 04/01/2014
> > Call Trace:
> >  <TASK>
> >  __dump_stack lib/dump_stack.c:94 [inline]
> >  dump_stack_lvl+0x116/0x1b0 lib/dump_stack.c:120
> >  print_address_description mm/kasan/report.c:378 [inline]
> >  print_report+0xc0/0x5e0 mm/kasan/report.c:489
> >  kasan_report+0xbd/0xf0 mm/kasan/report.c:602
> >  zswap_compress mm/zswap.c:925 [inline]
> >  zswap_store_page mm/zswap.c:1426 [inline]
> >  zswap_store+0x2307/0x25e0 mm/zswap.c:1533
> >  swap_writepage+0x3a8/0xe50 mm/page_io.c:279
> >  pageout+0x3b9/0xa90 mm/vmscan.c:689
> >  shrink_folio_list+0x2988/0x4340 mm/vmscan.c:1367
> >  evict_folios+0x72b/0x1a10 mm/vmscan.c:4593
> >  try_to_shrink_lruvec+0x62b/0xa60 mm/vmscan.c:4789
> >  shrink_one+0x417/0x7c0 mm/vmscan.c:4834
> >  shrink_many mm/vmscan.c:4897 [inline]
> >  lru_gen_shrink_node mm/vmscan.c:4975 [inline]
> >  shrink_node+0x269a/0x3d60 mm/vmscan.c:5956
> >  kswapd_shrink_node mm/vmscan.c:6785 [inline]
> >  balance_pgdat+0xbe5/0x18c0 mm/vmscan.c:6977
> >  kswapd+0x6ff/0xd60 mm/vmscan.c:7246
> >  kthread+0x2ca/0x3b0 kernel/kthread.c:389
> >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> >  </TASK>
> >
> > Allocated by task 1:
> >  kasan_save_stack+0x24/0x50 mm/kasan/common.c:47
> >  kasan_save_track+0x14/0x30 mm/kasan/common.c:68
> >  poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
> >  __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
> >  kasan_kmalloc include/linux/kasan.h:260 [inline]
> >  __do_kmalloc_node mm/slub.c:4283 [inline]
> >  __kmalloc_noprof+0x212/0x530 mm/slub.c:4295
> >  kmalloc_noprof include/linux/slab.h:905 [inline]
> >  kzalloc_noprof include/linux/slab.h:1037 [inline]
> >  __acomp_request_alloc_noprof include/crypto/internal/acompress.h:75 [inline]
> >  acomp_request_alloc+0x46/0x110 crypto/acompress.c:131
> >  zswap_cpu_comp_prepare+0x1f4/0x470 mm/zswap.c:840
> >  cpuhp_invoke_callback+0x26d/0x9d0 kernel/cpu.c:204
> >  cpuhp_issue_call+0x1c1/0x8d0 kernel/cpu.c:2375
> >  __cpuhp_state_add_instance_cpuslocked+0x26a/0x3c0 kernel/cpu.c:2437
> >  __cpuhp_state_add_instance+0xd7/0x2e0 kernel/cpu.c:2458
> >  cpuhp_state_add_instance include/linux/cpuhotplug.h:386 [inline]
> >  zswap_pool_create+0x2c3/0x5c0 mm/zswap.c:288
> >  __zswap_pool_create_fallback mm/zswap.c:356 [inline]
> >  zswap_setup+0x3a5/0x820 mm/zswap.c:1781
> >  zswap_init+0x2d/0x40 mm/zswap.c:1817
> >  do_one_initcall+0x111/0x6d0 init/main.c:1266
> >  do_initcall_level init/main.c:1328 [inline]
> >  do_initcalls init/main.c:1344 [inline]
> >  do_basic_setup init/main.c:1363 [inline]
> >  kernel_init_freeable+0x5ae/0x8a0 init/main.c:1577
> >  kernel_init+0x1e/0x2d0 init/main.c:1466
> >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> >
> > Freed by task 901:
> >  kasan_save_stack+0x24/0x50 mm/kasan/common.c:47
> >  kasan_save_track+0x14/0x30 mm/kasan/common.c:68
> >  kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:582
> >  poison_slab_object mm/kasan/common.c:247 [inline]
> >  __kasan_slab_free+0x54/0x70 mm/kasan/common.c:264
> >  kasan_slab_free include/linux/kasan.h:233 [inline]
> >  slab_free_hook mm/slub.c:2338 [inline]
> >  slab_free mm/slub.c:4598 [inline]
> >  kfree+0x14e/0x4d0 mm/slub.c:4746
> >  zswap_cpu_comp_dead+0xe3/0x1c0 mm/zswap.c:874
> >  cpuhp_invoke_callback+0x564/0x9d0 kernel/cpu.c:216
> >  __cpuhp_invoke_callback_range+0x104/0x220 kernel/cpu.c:965
> >  cpuhp_invoke_callback_range kernel/cpu.c:989 [inline]
> >  cpuhp_down_callbacks kernel/cpu.c:1382 [inline]
> >  _cpu_down+0x41d/0xef0 kernel/cpu.c:1443
> >  __cpu_down_maps_locked+0x6f/0x90 kernel/cpu.c:1473
> >  work_for_cpu_fn+0x55/0xa0 kernel/workqueue.c:6719
> >  process_one_work+0x9a2/0x1ba0 kernel/workqueue.c:3229
> >  process_scheduled_works kernel/workqueue.c:3310 [inline]
> >  worker_thread+0x677/0xe90 kernel/workqueue.c:3391
> >  kthread+0x2ca/0x3b0 kernel/kthread.c:389
> >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> >
> > The buggy address belongs to the object at ffff8880219f6b00
> >  which belongs to the cache kmalloc-96 of size 96
> > The buggy address is located 68 bytes inside of
> >  freed 96-byte region [ffff8880219f6b00, ffff8880219f6b60)
> >
> > The buggy address belongs to the physical page:
> > page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x219f6
> > anon flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
> > page_type: f5(slab)
> > raw: 00fff00000000000 ffff88801b041280 ffffea0000887d00 dead000000000005
> > raw: 0000000000000000 0000000000200020 00000001f5000000 0000000000000000
> > page dumped because: kasan: bad access detected
> > page_owner tracks the page as allocated
> > page last allocated via order 0, migratetype Unmovable, gfp_mask
> > 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 1, tgid
> > 1 (swapper/0), ts 15792736110, free_ts 14433067061
> >  set_page_owner include/linux/page_owner.h:32 [inline]
> >  post_alloc_hook+0x2e7/0x350 mm/page_alloc.c:1556
> >  prep_new_page mm/page_alloc.c:1564 [inline]
> >  get_page_from_freelist+0xe4e/0x2b20 mm/page_alloc.c:3474
> >  __alloc_pages_noprof+0x219/0x21f0 mm/page_alloc.c:4751
> >  alloc_pages_mpol_noprof+0x2b6/0x600 mm/mempolicy.c:2265
> >  alloc_slab_page mm/slub.c:2408 [inline]
> >  allocate_slab mm/slub.c:2574 [inline]
> >  new_slab+0x2d5/0x420 mm/slub.c:2627
> >  ___slab_alloc+0xbb7/0x1850 mm/slub.c:3815
> >  __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3905
> >  __slab_alloc_node mm/slub.c:3980 [inline]
> >  slab_alloc_node mm/slub.c:4141 [inline]
> >  __kmalloc_cache_noprof+0x280/0x410 mm/slub.c:4309
> >  kmalloc_noprof include/linux/slab.h:901 [inline]
> >  kzalloc_noprof include/linux/slab.h:1037 [inline]
> >  usb_hub_create_port_device+0xbb/0xde0 drivers/usb/core/port.c:743
> >  hub_configure drivers/usb/core/hub.c:1710 [inline]
> >  hub_probe+0x1ceb/0x2fc0 drivers/usb/core/hub.c:1965
> >  usb_probe_interface+0x314/0x9f0 drivers/usb/core/driver.c:399
> >  call_driver_probe drivers/base/dd.c:579 [inline]
> >  really_probe+0x252/0xa90 drivers/base/dd.c:658
> >  __driver_probe_device+0x1df/0x450 drivers/base/dd.c:800
> >  driver_probe_device+0x4c/0x1a0 drivers/base/dd.c:830
> >  __device_attach_driver+0x1db/0x2f0 drivers/base/dd.c:958
> >  bus_for_each_drv+0x14c/0x1d0 drivers/base/bus.c:459
> > page last free pid 25 tgid 25 stack trace:
> >  reset_page_owner include/linux/page_owner.h:25 [inline]
> >  free_pages_prepare mm/page_alloc.c:1127 [inline]
> >  free_unref_page+0x714/0x10c0 mm/page_alloc.c:2657
> >  vfree+0x17e/0x890 mm/vmalloc.c:3382
> >  delayed_vfree_work+0x57/0x70 mm/vmalloc.c:3303
> >  process_one_work+0x9a2/0x1ba0 kernel/workqueue.c:3229
> >  process_scheduled_works kernel/workqueue.c:3310 [inline]
> >  worker_thread+0x677/0xe90 kernel/workqueue.c:3391
> >  kthread+0x2ca/0x3b0 kernel/kthread.c:389
> >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> >
> > Memory state around the buggy address:
> >  ffff8880219f6a00: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
> >  ffff8880219f6a80: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
> > >ffff8880219f6b00: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> >                                            ^
> >  ffff8880219f6b80: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
> >  ffff8880219f6c00: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> > ==================================================================
> > If you have any questions, please contact us.
> >
> > Best Regards,
> > Yue

[-- Attachment #2: 0001-mm-zswap-fix-race-between-de-compression-and-CPU-hot.patch --]
[-- Type: application/octet-stream, Size: 2948 bytes --]

From 6bacd9bccf9d2e8b2de9a2e574243a6523b1b205 Mon Sep 17 00:00:00 2001
From: Yosry Ahmed <yosryahmed@google.com>
Date: Tue, 17 Dec 2024 19:17:06 +0000
Subject: [PATCH] mm: zswap: fix race between [de]compression and CPU hotunplug

In zswap_compress() and zswap_decompress(), the per-CPU acomp_ctx of the
current CPU at the beginning of the operation is used. However, since
neither preemption nor migration are disabled, it is possible that the
operation continues on a different CPU.

If the original CPU is hotunplugged while the acomp_ctx is still in use,
we run into a UAF bug. There are a few ways to fix this:
(a) Add a refcount for acomp_ctx.
(b) Disable migration while using the per-CPU acomp_ctx.
(c) Disable CPU hotunplug while using the per-CPU acomp_ctx.

Implement (c) since it's simpler than (a), and (b) involves using
migrate_disable() which is apparently discouraged.

Reported-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Sam Sun <samsun1006219@gmail.com>
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
---
 mm/zswap.c | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index 0030ce8fecfc5..0f57c98fcb135 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -875,6 +875,21 @@ static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node)
 	return 0;
 }
 
+static struct crypto_acomp_ctx *acomp_ctx_get_cpu(struct crypto_acomp_ctx __percpu *acomp_ctx)
+{
+	/*
+	 * Prevent CPU hotplug from freeing this CPU's acomp_ctx until
+	 * acomp_ctx_put_cpu().
+	 */
+	cpus_read_lock();
+	return raw_cpu_ptr(acomp_ctx);
+}
+
+static void acomp_ctx_put_cpu(void)
+{
+	cpus_read_unlock();
+}
+
 static bool zswap_compress(struct folio *folio, struct zswap_entry *entry)
 {
 	struct crypto_acomp_ctx *acomp_ctx;
@@ -887,8 +902,7 @@ static bool zswap_compress(struct folio *folio, struct zswap_entry *entry)
 	gfp_t gfp;
 	u8 *dst;
 
-	acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
-
+	acomp_ctx = acomp_ctx_get_cpu(entry->pool->acomp_ctx);
 	mutex_lock(&acomp_ctx->mutex);
 
 	dst = acomp_ctx->buffer;
@@ -944,6 +958,7 @@ static bool zswap_compress(struct folio *folio, struct zswap_entry *entry)
 		zswap_reject_alloc_fail++;
 
 	mutex_unlock(&acomp_ctx->mutex);
+	acomp_ctx_put_cpu();
 	return comp_ret == 0 && alloc_ret == 0;
 }
 
@@ -954,7 +969,7 @@ static void zswap_decompress(struct zswap_entry *entry, struct folio *folio)
 	struct crypto_acomp_ctx *acomp_ctx;
 	u8 *src;
 
-	acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
+	acomp_ctx = acomp_ctx_get_cpu(entry->pool->acomp_ctx);
 	mutex_lock(&acomp_ctx->mutex);
 
 	src = zpool_map_handle(zpool, entry->handle, ZPOOL_MM_RO);
@@ -984,6 +999,7 @@ static void zswap_decompress(struct zswap_entry *entry, struct folio *folio)
 
 	if (src != acomp_ctx->buffer)
 		zpool_unmap_handle(zpool, entry->handle);
+	acomp_ctx_put_cpu();
 }
 
 /*********************************
-- 
2.47.1.613.gc27f4b7a9f-goog

Re: [Bug] KASAN: slab-use-after-free Read in zswap_decompress

[Sam Sun]

On Wed, Dec 18, 2024 at 3:32 AM Yosry Ahmed <yosryahmed@google.com> wrote:
>
> On Tue, Dec 17, 2024 at 8:30 AM Yosry Ahmed <yosryahmed@google.com> wrote:
> >
> > On Tue, Dec 17, 2024 at 2:52 AM Sam Sun <samsun1006219@gmail.com> wrote:
> > >
> > > Dear developers and maintainers,
> > >
> > > We encountered a slab-use-after-free bug while using our modified
> > > syzkaller. Kernel crash log is listed below.
> >
> >
> > Thanks for reporting this!
> >
> > This seems to be the problem that Johannes pointed out in:
> > https://lore.kernel.org/lkml/20241113213007.GB1564047@cmpxchg.org/.
> >
> > Would you be able to check if the following diff fixes the problem?
>
> I sent a poached semi-staged git diff, apologies. Please try the
> proper patch attached instead.
>

I am sorry that I don't have a PoC that can trigger this bug. But
according to your analysis, I think this patch can fix the bug
properly.

>
> >
> > diff --git a/mm/zswap.c b/mm/zswap.c
> > index 0030ce8fecfc5..089d70dee3246 100644
> > --- a/mm/zswap.c
> > +++ b/mm/zswap.c
> > @@ -875,6 +875,21 @@ static int zswap_cpu_comp_dead(unsigned int cpu,
> > struct hlist_node *node)
> >         return 0;
> >  }
> >
> > +static void acomp_ctx_get_cpu(struct crypto_acomp_ctx *acomp_ctx)
> > +{
> > +       /*
> > +        * Prevent CPU hotplug from freeing this CPU's acomp_ctx until
> > +        * acomp_ctx_put_cpu().
> > +        */
> > +       cpus_read_lock();
> > +       return raw_cpu_ptr
> > +}
> > +
> > +static void acomp_ctx_put_cpu(void)
> > +{
> > +       cpus_read_unlock();
> > +}
> > +
> >  static bool zswap_compress(struct folio *folio, struct zswap_entry *entry)
> >  {
> >         struct crypto_acomp_ctx *acomp_ctx;
> > @@ -887,8 +902,7 @@ static bool zswap_compress(struct folio *folio,
> > struct zswap_entry *entry)
> >         gfp_t gfp;
> >         u8 *dst;
> >
> > -       acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
> > -
> > +       acomp_ctx = acomp_ctx_get_cpu(entry->pool->acomp_ctx);
> >         mutex_lock(&acomp_ctx->mutex);
> >
> >         dst = acomp_ctx->buffer;
> > @@ -944,6 +958,7 @@ static bool zswap_compress(struct folio *folio,
> > struct zswap_entry *entry)
> >                 zswap_reject_alloc_fail++;
> >
> >         mutex_unlock(&acomp_ctx->mutex);
> > +       acomp_ctx_put_cpu();
> >         return comp_ret == 0 && alloc_ret == 0;
> >  }
> >
> > @@ -954,7 +969,7 @@ static void zswap_decompress(struct zswap_entry
> > *entry, struct folio *folio)
> >         struct crypto_acomp_ctx *acomp_ctx;
> >         u8 *src;
> >
> > -       acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
> > +       acomp_ctx = acompx_ctx_get_cpu(entry->pool->acomp_ctx);
> >         mutex_lock(&acomp_ctx->mutex);
> >
> >         src = zpool_map_handle(zpool, entry->handle, ZPOOL_MM_RO);
> > @@ -984,6 +999,7 @@ static void zswap_decompress(struct zswap_entry
> > *entry, struct folio *folio)
> >
> >         if (src != acomp_ctx->buffer)
> >                 zpool_unmap_handle(zpool, entry->handle);
> > +       acomp_ctx_put_cpu();
> >  }
> >
> >  /*********************************
> >
> >
> > >
> > >
> > > ==================================================================
> > > BUG: KASAN: slab-use-after-free in zswap_decompress+0x7d7/0x810 mm/zswap.c:988
> > > Read of size 4 at addr ffff888027874044 by task kswapd0/92
> > >
> > > CPU: 1 UID: 0 PID: 92 Comm: kswapd0 Not tainted 6.12.0-09435-g2c22dc1ee3a1 #11
> > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> > > rel-1.16.1-0-g3208b098f51a-prebuilt.qemu.org 04/01/2014
> > > Call Trace:
> > >  <TASK>
> > >  __dump_stack lib/dump_stack.c:94 [inline]
> > >  dump_stack_lvl+0x116/0x1b0 lib/dump_stack.c:120
> > >  print_address_description mm/kasan/report.c:378 [inline]
> > >  print_report+0xc0/0x5e0 mm/kasan/report.c:489
> > >  kasan_report+0xbd/0xf0 mm/kasan/report.c:602
> > >  zswap_decompress+0x7d7/0x810 mm/zswap.c:988
> > >  zswap_writeback_entry+0x1e9/0x860 mm/zswap.c:1058
> > >  shrink_memcg_cb+0x213/0x360 mm/zswap.c:1163
> > >  __list_lru_walk_one+0x15e/0x490 mm/list_lru.c:301
> > >  list_lru_walk_one+0x3e/0x50 mm/list_lru.c:338
> > >  list_lru_shrink_walk include/linux/list_lru.h:240 [inline]
> > >  zswap_shrinker_scan+0x135/0x220 mm/zswap.c:1197
> > >  do_shrink_slab+0x44e/0x1190 mm/shrinker.c:437
> > >  shrink_slab_memcg mm/shrinker.c:550 [inline]
> > >  shrink_slab+0xb61/0x12a0 mm/shrinker.c:628
> > >  shrink_one+0x4ad/0x7c0 mm/vmscan.c:4836
> > >  shrink_many mm/vmscan.c:4897 [inline]
> > >  lru_gen_shrink_node mm/vmscan.c:4975 [inline]
> > >  shrink_node+0x269a/0x3d60 mm/vmscan.c:5956
> > >  kswapd_shrink_node mm/vmscan.c:6785 [inline]
> > >  balance_pgdat+0xbe5/0x18c0 mm/vmscan.c:6977
> > >  kswapd+0x6ff/0xd60 mm/vmscan.c:7246
> > >  kthread+0x2ca/0x3b0 kernel/kthread.c:389
> > >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> > >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> > >  </TASK>
> > >
> > > Allocated by task 1:
> > >  kasan_save_stack+0x24/0x50 mm/kasan/common.c:47
> > >  kasan_save_track+0x14/0x30 mm/kasan/common.c:68
> > >  poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
> > >  __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
> > >  kasan_kmalloc include/linux/kasan.h:260 [inline]
> > >  __do_kmalloc_node mm/slub.c:4283 [inline]
> > >  __kmalloc_noprof+0x212/0x530 mm/slub.c:4295
> > >  kmalloc_noprof include/linux/slab.h:905 [inline]
> > >  kzalloc_noprof include/linux/slab.h:1037 [inline]
> > >  __acomp_request_alloc_noprof include/crypto/internal/acompress.h:75 [inline]
> > >  acomp_request_alloc+0x46/0x110 crypto/acompress.c:131
> > >  zswap_cpu_comp_prepare+0x1f4/0x470 mm/zswap.c:840
> > >  cpuhp_invoke_callback+0x26d/0x9d0 kernel/cpu.c:204
> > >  cpuhp_issue_call+0x1c1/0x8d0 kernel/cpu.c:2375
> > >  __cpuhp_state_add_instance_cpuslocked+0x26a/0x3c0 kernel/cpu.c:2437
> > >  __cpuhp_state_add_instance+0xd7/0x2e0 kernel/cpu.c:2458
> > >  cpuhp_state_add_instance include/linux/cpuhotplug.h:386 [inline]
> > >  zswap_pool_create+0x2c3/0x5c0 mm/zswap.c:288
> > >  __zswap_pool_create_fallback mm/zswap.c:356 [inline]
> > >  zswap_setup+0x3a5/0x820 mm/zswap.c:1781
> > >  zswap_init+0x2d/0x40 mm/zswap.c:1817
> > >  do_one_initcall+0x111/0x6d0 init/main.c:1266
> > >  do_initcall_level init/main.c:1328 [inline]
> > >  do_initcalls init/main.c:1344 [inline]
> > >  do_basic_setup init/main.c:1363 [inline]
> > >  kernel_init_freeable+0x5ae/0x8a0 init/main.c:1577
> > >  kernel_init+0x1e/0x2d0 init/main.c:1466
> > >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> > >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> > >
> > > Freed by task 25:
> > >  kasan_save_stack+0x24/0x50 mm/kasan/common.c:47
> > >  kasan_save_track+0x14/0x30 mm/kasan/common.c:68
> > >  kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:582
> > >  poison_slab_object mm/kasan/common.c:247 [inline]
> > >  __kasan_slab_free+0x54/0x70 mm/kasan/common.c:264
> > >  kasan_slab_free include/linux/kasan.h:233 [inline]
> > >  slab_free_hook mm/slub.c:2338 [inline]
> > >  slab_free mm/slub.c:4598 [inline]
> > >  kfree+0x14e/0x4d0 mm/slub.c:4746
> > >  zswap_cpu_comp_dead+0xe3/0x1c0 mm/zswap.c:874
> > >  cpuhp_invoke_callback+0x564/0x9d0 kernel/cpu.c:216
> > >  __cpuhp_invoke_callback_range+0x104/0x220 kernel/cpu.c:965
> > >  cpuhp_invoke_callback_range kernel/cpu.c:989 [inline]
> > >  cpuhp_down_callbacks kernel/cpu.c:1382 [inline]
> > >  _cpu_down+0x41d/0xef0 kernel/cpu.c:1443
> > >  __cpu_down_maps_locked+0x6f/0x90 kernel/cpu.c:1473
> > >  work_for_cpu_fn+0x55/0xa0 kernel/workqueue.c:6719
> > >  process_one_work+0x9a2/0x1ba0 kernel/workqueue.c:3229
> > >  process_scheduled_works kernel/workqueue.c:3310 [inline]
> > >  worker_thread+0x677/0xe90 kernel/workqueue.c:3391
> > >  kthread+0x2ca/0x3b0 kernel/kthread.c:389
> > >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> > >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> > >
> > > The buggy address belongs to the object at ffff888027874000
> > >  which belongs to the cache kmalloc-96 of size 96
> > > The buggy address is located 68 bytes inside of
> > >  freed 96-byte region [ffff888027874000, ffff888027874060)
> > >
> > > The buggy address belongs to the physical page:
> > > page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x27874
> > > flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
> > > page_type: f5(slab)
> > > raw: 00fff00000000000 ffff88801b041280 dead000000000100 dead000000000122
> > > raw: 0000000000000000 0000000000200020 00000001f5000000 0000000000000000
> > > page dumped because: kasan: bad access detected
> > > page_owner tracks the page as allocated
> > > page last allocated via order 0, migratetype Unmovable, gfp_mask
> > > 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 1, tgid
> > > 1 (swapper/0), ts 20389586985, free_ts 18720773637
> > >  set_page_owner include/linux/page_owner.h:32 [inline]
> > >  post_alloc_hook+0x2e7/0x350 mm/page_alloc.c:1556
> > >  prep_new_page mm/page_alloc.c:1564 [inline]
> > >  get_page_from_freelist+0xe4e/0x2b20 mm/page_alloc.c:3474
> > >  __alloc_pages_noprof+0x219/0x21f0 mm/page_alloc.c:4751
> > >  alloc_pages_mpol_noprof+0x2b6/0x600 mm/mempolicy.c:2265
> > >  alloc_slab_page mm/slub.c:2408 [inline]
> > >  allocate_slab mm/slub.c:2574 [inline]
> > >  new_slab+0x2d5/0x420 mm/slub.c:2627
> > >  ___slab_alloc+0xbb7/0x1850 mm/slub.c:3815
> > >  __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3905
> > >  __slab_alloc_node mm/slub.c:3980 [inline]
> > >  slab_alloc_node mm/slub.c:4141 [inline]
> > >  __do_kmalloc_node mm/slub.c:4282 [inline]
> > >  __kmalloc_noprof+0x2ac/0x530 mm/slub.c:4295
> > >  kmalloc_noprof include/linux/slab.h:905 [inline]
> > >  kzalloc_noprof include/linux/slab.h:1037 [inline]
> > >  __acomp_request_alloc_noprof include/crypto/internal/acompress.h:75 [inline]
> > >  acomp_request_alloc+0x46/0x110 crypto/acompress.c:131
> > >  zswap_cpu_comp_prepare+0x1f4/0x470 mm/zswap.c:840
> > >  cpuhp_invoke_callback+0x26d/0x9d0 kernel/cpu.c:204
> > >  cpuhp_issue_call+0x1c1/0x8d0 kernel/cpu.c:2375
> > >  __cpuhp_state_add_instance_cpuslocked+0x26a/0x3c0 kernel/cpu.c:2437
> > >  __cpuhp_state_add_instance+0xd7/0x2e0 kernel/cpu.c:2458
> > >  cpuhp_state_add_instance include/linux/cpuhotplug.h:386 [inline]
> > >  zswap_pool_create+0x2c3/0x5c0 mm/zswap.c:288
> > >  __zswap_pool_create_fallback mm/zswap.c:356 [inline]
> > >  zswap_setup+0x3a5/0x820 mm/zswap.c:1781
> > > page last free pid 54 tgid 54 stack trace:
> > >  reset_page_owner include/linux/page_owner.h:25 [inline]
> > >  free_pages_prepare mm/page_alloc.c:1127 [inline]
> > >  free_unref_page+0x714/0x10c0 mm/page_alloc.c:2657
> > >  vfree+0x17e/0x890 mm/vmalloc.c:3382
> > >  delayed_vfree_work+0x57/0x70 mm/vmalloc.c:3303
> > >  process_one_work+0x9a2/0x1ba0 kernel/workqueue.c:3229
> > >  process_scheduled_works kernel/workqueue.c:3310 [inline]
> > >  worker_thread+0x677/0xe90 kernel/workqueue.c:3391
> > >  kthread+0x2ca/0x3b0 kernel/kthread.c:389
> > >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> > >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> > >
> > > Memory state around the buggy address:
> > >  ffff888027873f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> > >  ffff888027873f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> > > >ffff888027874000: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> > >                                            ^
> > >  ffff888027874080: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
> > >  ffff888027874100: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
> > > ==================================================================
> > > We also find a similar bug report in function zswap_store(), listed as below:
> > >
> > > ==================================================================
> > > BUG: KASAN: slab-use-after-free in zswap_compress mm/zswap.c:925 [inline]
> > > BUG: KASAN: slab-use-after-free in zswap_store_page mm/zswap.c:1426 [inline]
> > > BUG: KASAN: slab-use-after-free in zswap_store+0x2307/0x25e0 mm/zswap.c:1533
> > > Read of size 4 at addr ffff8880219f6b44 by task kswapd0/88
> > >
> > > CPU: 1 UID: 0 PID: 88 Comm: kswapd0 Tainted: G     U
> > > 6.12.0-09435-g2c22dc1ee3a1 #11
> > > Tainted: [U]=USER
> > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> > > rel-1.16.1-0-g3208b098f51a-prebuilt.qemu.org 04/01/2014
> > > Call Trace:
> > >  <TASK>
> > >  __dump_stack lib/dump_stack.c:94 [inline]
> > >  dump_stack_lvl+0x116/0x1b0 lib/dump_stack.c:120
> > >  print_address_description mm/kasan/report.c:378 [inline]
> > >  print_report+0xc0/0x5e0 mm/kasan/report.c:489
> > >  kasan_report+0xbd/0xf0 mm/kasan/report.c:602
> > >  zswap_compress mm/zswap.c:925 [inline]
> > >  zswap_store_page mm/zswap.c:1426 [inline]
> > >  zswap_store+0x2307/0x25e0 mm/zswap.c:1533
> > >  swap_writepage+0x3a8/0xe50 mm/page_io.c:279
> > >  pageout+0x3b9/0xa90 mm/vmscan.c:689
> > >  shrink_folio_list+0x2988/0x4340 mm/vmscan.c:1367
> > >  evict_folios+0x72b/0x1a10 mm/vmscan.c:4593
> > >  try_to_shrink_lruvec+0x62b/0xa60 mm/vmscan.c:4789
> > >  shrink_one+0x417/0x7c0 mm/vmscan.c:4834
> > >  shrink_many mm/vmscan.c:4897 [inline]
> > >  lru_gen_shrink_node mm/vmscan.c:4975 [inline]
> > >  shrink_node+0x269a/0x3d60 mm/vmscan.c:5956
> > >  kswapd_shrink_node mm/vmscan.c:6785 [inline]
> > >  balance_pgdat+0xbe5/0x18c0 mm/vmscan.c:6977
> > >  kswapd+0x6ff/0xd60 mm/vmscan.c:7246
> > >  kthread+0x2ca/0x3b0 kernel/kthread.c:389
> > >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> > >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> > >  </TASK>
> > >
> > > Allocated by task 1:
> > >  kasan_save_stack+0x24/0x50 mm/kasan/common.c:47
> > >  kasan_save_track+0x14/0x30 mm/kasan/common.c:68
> > >  poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
> > >  __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
> > >  kasan_kmalloc include/linux/kasan.h:260 [inline]
> > >  __do_kmalloc_node mm/slub.c:4283 [inline]
> > >  __kmalloc_noprof+0x212/0x530 mm/slub.c:4295
> > >  kmalloc_noprof include/linux/slab.h:905 [inline]
> > >  kzalloc_noprof include/linux/slab.h:1037 [inline]
> > >  __acomp_request_alloc_noprof include/crypto/internal/acompress.h:75 [inline]
> > >  acomp_request_alloc+0x46/0x110 crypto/acompress.c:131
> > >  zswap_cpu_comp_prepare+0x1f4/0x470 mm/zswap.c:840
> > >  cpuhp_invoke_callback+0x26d/0x9d0 kernel/cpu.c:204
> > >  cpuhp_issue_call+0x1c1/0x8d0 kernel/cpu.c:2375
> > >  __cpuhp_state_add_instance_cpuslocked+0x26a/0x3c0 kernel/cpu.c:2437
> > >  __cpuhp_state_add_instance+0xd7/0x2e0 kernel/cpu.c:2458
> > >  cpuhp_state_add_instance include/linux/cpuhotplug.h:386 [inline]
> > >  zswap_pool_create+0x2c3/0x5c0 mm/zswap.c:288
> > >  __zswap_pool_create_fallback mm/zswap.c:356 [inline]
> > >  zswap_setup+0x3a5/0x820 mm/zswap.c:1781
> > >  zswap_init+0x2d/0x40 mm/zswap.c:1817
> > >  do_one_initcall+0x111/0x6d0 init/main.c:1266
> > >  do_initcall_level init/main.c:1328 [inline]
> > >  do_initcalls init/main.c:1344 [inline]
> > >  do_basic_setup init/main.c:1363 [inline]
> > >  kernel_init_freeable+0x5ae/0x8a0 init/main.c:1577
> > >  kernel_init+0x1e/0x2d0 init/main.c:1466
> > >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> > >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> > >
> > > Freed by task 901:
> > >  kasan_save_stack+0x24/0x50 mm/kasan/common.c:47
> > >  kasan_save_track+0x14/0x30 mm/kasan/common.c:68
> > >  kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:582
> > >  poison_slab_object mm/kasan/common.c:247 [inline]
> > >  __kasan_slab_free+0x54/0x70 mm/kasan/common.c:264
> > >  kasan_slab_free include/linux/kasan.h:233 [inline]
> > >  slab_free_hook mm/slub.c:2338 [inline]
> > >  slab_free mm/slub.c:4598 [inline]
> > >  kfree+0x14e/0x4d0 mm/slub.c:4746
> > >  zswap_cpu_comp_dead+0xe3/0x1c0 mm/zswap.c:874
> > >  cpuhp_invoke_callback+0x564/0x9d0 kernel/cpu.c:216
> > >  __cpuhp_invoke_callback_range+0x104/0x220 kernel/cpu.c:965
> > >  cpuhp_invoke_callback_range kernel/cpu.c:989 [inline]
> > >  cpuhp_down_callbacks kernel/cpu.c:1382 [inline]
> > >  _cpu_down+0x41d/0xef0 kernel/cpu.c:1443
> > >  __cpu_down_maps_locked+0x6f/0x90 kernel/cpu.c:1473
> > >  work_for_cpu_fn+0x55/0xa0 kernel/workqueue.c:6719
> > >  process_one_work+0x9a2/0x1ba0 kernel/workqueue.c:3229
> > >  process_scheduled_works kernel/workqueue.c:3310 [inline]
> > >  worker_thread+0x677/0xe90 kernel/workqueue.c:3391
> > >  kthread+0x2ca/0x3b0 kernel/kthread.c:389
> > >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> > >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> > >
> > > The buggy address belongs to the object at ffff8880219f6b00
> > >  which belongs to the cache kmalloc-96 of size 96
> > > The buggy address is located 68 bytes inside of
> > >  freed 96-byte region [ffff8880219f6b00, ffff8880219f6b60)
> > >
> > > The buggy address belongs to the physical page:
> > > page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x219f6
> > > anon flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
> > > page_type: f5(slab)
> > > raw: 00fff00000000000 ffff88801b041280 ffffea0000887d00 dead000000000005
> > > raw: 0000000000000000 0000000000200020 00000001f5000000 0000000000000000
> > > page dumped because: kasan: bad access detected
> > > page_owner tracks the page as allocated
> > > page last allocated via order 0, migratetype Unmovable, gfp_mask
> > > 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 1, tgid
> > > 1 (swapper/0), ts 15792736110, free_ts 14433067061
> > >  set_page_owner include/linux/page_owner.h:32 [inline]
> > >  post_alloc_hook+0x2e7/0x350 mm/page_alloc.c:1556
> > >  prep_new_page mm/page_alloc.c:1564 [inline]
> > >  get_page_from_freelist+0xe4e/0x2b20 mm/page_alloc.c:3474
> > >  __alloc_pages_noprof+0x219/0x21f0 mm/page_alloc.c:4751
> > >  alloc_pages_mpol_noprof+0x2b6/0x600 mm/mempolicy.c:2265
> > >  alloc_slab_page mm/slub.c:2408 [inline]
> > >  allocate_slab mm/slub.c:2574 [inline]
> > >  new_slab+0x2d5/0x420 mm/slub.c:2627
> > >  ___slab_alloc+0xbb7/0x1850 mm/slub.c:3815
> > >  __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3905
> > >  __slab_alloc_node mm/slub.c:3980 [inline]
> > >  slab_alloc_node mm/slub.c:4141 [inline]
> > >  __kmalloc_cache_noprof+0x280/0x410 mm/slub.c:4309
> > >  kmalloc_noprof include/linux/slab.h:901 [inline]
> > >  kzalloc_noprof include/linux/slab.h:1037 [inline]
> > >  usb_hub_create_port_device+0xbb/0xde0 drivers/usb/core/port.c:743
> > >  hub_configure drivers/usb/core/hub.c:1710 [inline]
> > >  hub_probe+0x1ceb/0x2fc0 drivers/usb/core/hub.c:1965
> > >  usb_probe_interface+0x314/0x9f0 drivers/usb/core/driver.c:399
> > >  call_driver_probe drivers/base/dd.c:579 [inline]
> > >  really_probe+0x252/0xa90 drivers/base/dd.c:658
> > >  __driver_probe_device+0x1df/0x450 drivers/base/dd.c:800
> > >  driver_probe_device+0x4c/0x1a0 drivers/base/dd.c:830
> > >  __device_attach_driver+0x1db/0x2f0 drivers/base/dd.c:958
> > >  bus_for_each_drv+0x14c/0x1d0 drivers/base/bus.c:459
> > > page last free pid 25 tgid 25 stack trace:
> > >  reset_page_owner include/linux/page_owner.h:25 [inline]
> > >  free_pages_prepare mm/page_alloc.c:1127 [inline]
> > >  free_unref_page+0x714/0x10c0 mm/page_alloc.c:2657
> > >  vfree+0x17e/0x890 mm/vmalloc.c:3382
> > >  delayed_vfree_work+0x57/0x70 mm/vmalloc.c:3303
> > >  process_one_work+0x9a2/0x1ba0 kernel/workqueue.c:3229
> > >  process_scheduled_works kernel/workqueue.c:3310 [inline]
> > >  worker_thread+0x677/0xe90 kernel/workqueue.c:3391
> > >  kthread+0x2ca/0x3b0 kernel/kthread.c:389
> > >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> > >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> > >
> > > Memory state around the buggy address:
> > >  ffff8880219f6a00: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
> > >  ffff8880219f6a80: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
> > > >ffff8880219f6b00: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> > >                                            ^
> > >  ffff8880219f6b80: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
> > >  ffff8880219f6c00: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> > > ==================================================================
> > > If you have any questions, please contact us.
> > >
> > > Best Regards,
> > > Yue

Re: [Bug] KASAN: slab-use-after-free Read in zswap_decompress

[Yosry Ahmed]

On Wed, Dec 18, 2024 at 1:17 AM Sam Sun <samsun1006219@gmail.com> wrote:
>
> On Wed, Dec 18, 2024 at 3:32 AM Yosry Ahmed <yosryahmed@google.com> wrote:
> >
> > On Tue, Dec 17, 2024 at 8:30 AM Yosry Ahmed <yosryahmed@google.com> wrote:
> > >
> > > On Tue, Dec 17, 2024 at 2:52 AM Sam Sun <samsun1006219@gmail.com> wrote:
> > > >
> > > > Dear developers and maintainers,
> > > >
> > > > We encountered a slab-use-after-free bug while using our modified
> > > > syzkaller. Kernel crash log is listed below.
> > >
> > >
> > > Thanks for reporting this!
> > >
> > > This seems to be the problem that Johannes pointed out in:
> > > https://lore.kernel.org/lkml/20241113213007.GB1564047@cmpxchg.org/.
> > >
> > > Would you be able to check if the following diff fixes the problem?
> >
> > I sent a poached semi-staged git diff, apologies. Please try the
> > proper patch attached instead.
> >
>
> I am sorry that I don't have a PoC that can trigger this bug. But
> according to your analysis, I think this patch can fix the bug
> properly.

I was able to reproduce this in a VM with a hacky diff that sets up
the race condition:

diff --git a/mm/zswap.c b/mm/zswap.c
index f6316b66fb236..e5f7341948924 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -893,8 +893,18 @@ static bool zswap_compress(struct page *page,
struct zswap_entry *entry,
        gfp_t gfp;
        u8 *dst;

+       set_cpus_allowed_ptr(current, cpumask_of(1));
+       pr_info("zswap_compress(): running on CPU %d\n", smp_processor_id());
+
        acomp_ctx = raw_cpu_ptr(pool->acomp_ctx);

+       set_cpus_allowed_ptr(current, cpumask_of(0));
+       pr_info("zswap_compress(): running on CPU %d\n", smp_processor_id());
+       pr_info("zswap_compress(): sleeping\n");
+
+       schedule_timeout_uninterruptible(msecs_to_jiffies(10*MSEC_PER_SEC));
+       pr_info("zswap_compress(): woke up on CPU %d\n", smp_processor_id());
+
        mutex_lock(&acomp_ctx->mutex);

        dst = acomp_ctx->buffer;

Running a user program that invokes zswap compression, after
"sleeping" is printed I manually offlined CPU 1 and I got a similar
KASAN UAF splat and a kernel crash due to faulting on an illegal
kernel address. This goes away with my fix and the offlining is
delayed until the end of zswap_compress(), so I will send it out
separately.

>
> >
> > >
> > > diff --git a/mm/zswap.c b/mm/zswap.c
> > > index 0030ce8fecfc5..089d70dee3246 100644
> > > --- a/mm/zswap.c
> > > +++ b/mm/zswap.c
> > > @@ -875,6 +875,21 @@ static int zswap_cpu_comp_dead(unsigned int cpu,
> > > struct hlist_node *node)
> > >         return 0;
> > >  }
> > >
> > > +static void acomp_ctx_get_cpu(struct crypto_acomp_ctx *acomp_ctx)
> > > +{
> > > +       /*
> > > +        * Prevent CPU hotplug from freeing this CPU's acomp_ctx until
> > > +        * acomp_ctx_put_cpu().
> > > +        */
> > > +       cpus_read_lock();
> > > +       return raw_cpu_ptr
> > > +}
> > > +
> > > +static void acomp_ctx_put_cpu(void)
> > > +{
> > > +       cpus_read_unlock();
> > > +}
> > > +
> > >  static bool zswap_compress(struct folio *folio, struct zswap_entry *entry)
> > >  {
> > >         struct crypto_acomp_ctx *acomp_ctx;
> > > @@ -887,8 +902,7 @@ static bool zswap_compress(struct folio *folio,
> > > struct zswap_entry *entry)
> > >         gfp_t gfp;
> > >         u8 *dst;
> > >
> > > -       acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
> > > -
> > > +       acomp_ctx = acomp_ctx_get_cpu(entry->pool->acomp_ctx);
> > >         mutex_lock(&acomp_ctx->mutex);
> > >
> > >         dst = acomp_ctx->buffer;
> > > @@ -944,6 +958,7 @@ static bool zswap_compress(struct folio *folio,
> > > struct zswap_entry *entry)
> > >                 zswap_reject_alloc_fail++;
> > >
> > >         mutex_unlock(&acomp_ctx->mutex);
> > > +       acomp_ctx_put_cpu();
> > >         return comp_ret == 0 && alloc_ret == 0;
> > >  }
> > >
> > > @@ -954,7 +969,7 @@ static void zswap_decompress(struct zswap_entry
> > > *entry, struct folio *folio)
> > >         struct crypto_acomp_ctx *acomp_ctx;
> > >         u8 *src;
> > >
> > > -       acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
> > > +       acomp_ctx = acompx_ctx_get_cpu(entry->pool->acomp_ctx);
> > >         mutex_lock(&acomp_ctx->mutex);
> > >
> > >         src = zpool_map_handle(zpool, entry->handle, ZPOOL_MM_RO);
> > > @@ -984,6 +999,7 @@ static void zswap_decompress(struct zswap_entry
> > > *entry, struct folio *folio)
> > >
> > >         if (src != acomp_ctx->buffer)
> > >                 zpool_unmap_handle(zpool, entry->handle);
> > > +       acomp_ctx_put_cpu();
> > >  }
> > >
> > >  /*********************************
> > >
> > >
> > > >
> > > >
> > > > ==================================================================
> > > > BUG: KASAN: slab-use-after-free in zswap_decompress+0x7d7/0x810 mm/zswap.c:988
> > > > Read of size 4 at addr ffff888027874044 by task kswapd0/92
> > > >
> > > > CPU: 1 UID: 0 PID: 92 Comm: kswapd0 Not tainted 6.12.0-09435-g2c22dc1ee3a1 #11
> > > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> > > > rel-1.16.1-0-g3208b098f51a-prebuilt.qemu.org 04/01/2014
> > > > Call Trace:
> > > >  <TASK>
> > > >  __dump_stack lib/dump_stack.c:94 [inline]
> > > >  dump_stack_lvl+0x116/0x1b0 lib/dump_stack.c:120
> > > >  print_address_description mm/kasan/report.c:378 [inline]
> > > >  print_report+0xc0/0x5e0 mm/kasan/report.c:489
> > > >  kasan_report+0xbd/0xf0 mm/kasan/report.c:602
> > > >  zswap_decompress+0x7d7/0x810 mm/zswap.c:988
> > > >  zswap_writeback_entry+0x1e9/0x860 mm/zswap.c:1058
> > > >  shrink_memcg_cb+0x213/0x360 mm/zswap.c:1163
> > > >  __list_lru_walk_one+0x15e/0x490 mm/list_lru.c:301
> > > >  list_lru_walk_one+0x3e/0x50 mm/list_lru.c:338
> > > >  list_lru_shrink_walk include/linux/list_lru.h:240 [inline]
> > > >  zswap_shrinker_scan+0x135/0x220 mm/zswap.c:1197
> > > >  do_shrink_slab+0x44e/0x1190 mm/shrinker.c:437
> > > >  shrink_slab_memcg mm/shrinker.c:550 [inline]
> > > >  shrink_slab+0xb61/0x12a0 mm/shrinker.c:628
> > > >  shrink_one+0x4ad/0x7c0 mm/vmscan.c:4836
> > > >  shrink_many mm/vmscan.c:4897 [inline]
> > > >  lru_gen_shrink_node mm/vmscan.c:4975 [inline]
> > > >  shrink_node+0x269a/0x3d60 mm/vmscan.c:5956
> > > >  kswapd_shrink_node mm/vmscan.c:6785 [inline]
> > > >  balance_pgdat+0xbe5/0x18c0 mm/vmscan.c:6977
> > > >  kswapd+0x6ff/0xd60 mm/vmscan.c:7246
> > > >  kthread+0x2ca/0x3b0 kernel/kthread.c:389
> > > >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> > > >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> > > >  </TASK>
> > > >
> > > > Allocated by task 1:
> > > >  kasan_save_stack+0x24/0x50 mm/kasan/common.c:47
> > > >  kasan_save_track+0x14/0x30 mm/kasan/common.c:68
> > > >  poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
> > > >  __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
> > > >  kasan_kmalloc include/linux/kasan.h:260 [inline]
> > > >  __do_kmalloc_node mm/slub.c:4283 [inline]
> > > >  __kmalloc_noprof+0x212/0x530 mm/slub.c:4295
> > > >  kmalloc_noprof include/linux/slab.h:905 [inline]
> > > >  kzalloc_noprof include/linux/slab.h:1037 [inline]
> > > >  __acomp_request_alloc_noprof include/crypto/internal/acompress.h:75 [inline]
> > > >  acomp_request_alloc+0x46/0x110 crypto/acompress.c:131
> > > >  zswap_cpu_comp_prepare+0x1f4/0x470 mm/zswap.c:840
> > > >  cpuhp_invoke_callback+0x26d/0x9d0 kernel/cpu.c:204
> > > >  cpuhp_issue_call+0x1c1/0x8d0 kernel/cpu.c:2375
> > > >  __cpuhp_state_add_instance_cpuslocked+0x26a/0x3c0 kernel/cpu.c:2437
> > > >  __cpuhp_state_add_instance+0xd7/0x2e0 kernel/cpu.c:2458
> > > >  cpuhp_state_add_instance include/linux/cpuhotplug.h:386 [inline]
> > > >  zswap_pool_create+0x2c3/0x5c0 mm/zswap.c:288
> > > >  __zswap_pool_create_fallback mm/zswap.c:356 [inline]
> > > >  zswap_setup+0x3a5/0x820 mm/zswap.c:1781
> > > >  zswap_init+0x2d/0x40 mm/zswap.c:1817
> > > >  do_one_initcall+0x111/0x6d0 init/main.c:1266
> > > >  do_initcall_level init/main.c:1328 [inline]
> > > >  do_initcalls init/main.c:1344 [inline]
> > > >  do_basic_setup init/main.c:1363 [inline]
> > > >  kernel_init_freeable+0x5ae/0x8a0 init/main.c:1577
> > > >  kernel_init+0x1e/0x2d0 init/main.c:1466
> > > >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> > > >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> > > >
> > > > Freed by task 25:
> > > >  kasan_save_stack+0x24/0x50 mm/kasan/common.c:47
> > > >  kasan_save_track+0x14/0x30 mm/kasan/common.c:68
> > > >  kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:582
> > > >  poison_slab_object mm/kasan/common.c:247 [inline]
> > > >  __kasan_slab_free+0x54/0x70 mm/kasan/common.c:264
> > > >  kasan_slab_free include/linux/kasan.h:233 [inline]
> > > >  slab_free_hook mm/slub.c:2338 [inline]
> > > >  slab_free mm/slub.c:4598 [inline]
> > > >  kfree+0x14e/0x4d0 mm/slub.c:4746
> > > >  zswap_cpu_comp_dead+0xe3/0x1c0 mm/zswap.c:874
> > > >  cpuhp_invoke_callback+0x564/0x9d0 kernel/cpu.c:216
> > > >  __cpuhp_invoke_callback_range+0x104/0x220 kernel/cpu.c:965
> > > >  cpuhp_invoke_callback_range kernel/cpu.c:989 [inline]
> > > >  cpuhp_down_callbacks kernel/cpu.c:1382 [inline]
> > > >  _cpu_down+0x41d/0xef0 kernel/cpu.c:1443
> > > >  __cpu_down_maps_locked+0x6f/0x90 kernel/cpu.c:1473
> > > >  work_for_cpu_fn+0x55/0xa0 kernel/workqueue.c:6719
> > > >  process_one_work+0x9a2/0x1ba0 kernel/workqueue.c:3229
> > > >  process_scheduled_works kernel/workqueue.c:3310 [inline]
> > > >  worker_thread+0x677/0xe90 kernel/workqueue.c:3391
> > > >  kthread+0x2ca/0x3b0 kernel/kthread.c:389
> > > >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> > > >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> > > >
> > > > The buggy address belongs to the object at ffff888027874000
> > > >  which belongs to the cache kmalloc-96 of size 96
> > > > The buggy address is located 68 bytes inside of
> > > >  freed 96-byte region [ffff888027874000, ffff888027874060)
> > > >
> > > > The buggy address belongs to the physical page:
> > > > page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x27874
> > > > flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
> > > > page_type: f5(slab)
> > > > raw: 00fff00000000000 ffff88801b041280 dead000000000100 dead000000000122
> > > > raw: 0000000000000000 0000000000200020 00000001f5000000 0000000000000000
> > > > page dumped because: kasan: bad access detected
> > > > page_owner tracks the page as allocated
> > > > page last allocated via order 0, migratetype Unmovable, gfp_mask
> > > > 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 1, tgid
> > > > 1 (swapper/0), ts 20389586985, free_ts 18720773637
> > > >  set_page_owner include/linux/page_owner.h:32 [inline]
> > > >  post_alloc_hook+0x2e7/0x350 mm/page_alloc.c:1556
> > > >  prep_new_page mm/page_alloc.c:1564 [inline]
> > > >  get_page_from_freelist+0xe4e/0x2b20 mm/page_alloc.c:3474
> > > >  __alloc_pages_noprof+0x219/0x21f0 mm/page_alloc.c:4751
> > > >  alloc_pages_mpol_noprof+0x2b6/0x600 mm/mempolicy.c:2265
> > > >  alloc_slab_page mm/slub.c:2408 [inline]
> > > >  allocate_slab mm/slub.c:2574 [inline]
> > > >  new_slab+0x2d5/0x420 mm/slub.c:2627
> > > >  ___slab_alloc+0xbb7/0x1850 mm/slub.c:3815
> > > >  __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3905
> > > >  __slab_alloc_node mm/slub.c:3980 [inline]
> > > >  slab_alloc_node mm/slub.c:4141 [inline]
> > > >  __do_kmalloc_node mm/slub.c:4282 [inline]
> > > >  __kmalloc_noprof+0x2ac/0x530 mm/slub.c:4295
> > > >  kmalloc_noprof include/linux/slab.h:905 [inline]
> > > >  kzalloc_noprof include/linux/slab.h:1037 [inline]
> > > >  __acomp_request_alloc_noprof include/crypto/internal/acompress.h:75 [inline]
> > > >  acomp_request_alloc+0x46/0x110 crypto/acompress.c:131
> > > >  zswap_cpu_comp_prepare+0x1f4/0x470 mm/zswap.c:840
> > > >  cpuhp_invoke_callback+0x26d/0x9d0 kernel/cpu.c:204
> > > >  cpuhp_issue_call+0x1c1/0x8d0 kernel/cpu.c:2375
> > > >  __cpuhp_state_add_instance_cpuslocked+0x26a/0x3c0 kernel/cpu.c:2437
> > > >  __cpuhp_state_add_instance+0xd7/0x2e0 kernel/cpu.c:2458
> > > >  cpuhp_state_add_instance include/linux/cpuhotplug.h:386 [inline]
> > > >  zswap_pool_create+0x2c3/0x5c0 mm/zswap.c:288
> > > >  __zswap_pool_create_fallback mm/zswap.c:356 [inline]
> > > >  zswap_setup+0x3a5/0x820 mm/zswap.c:1781
> > > > page last free pid 54 tgid 54 stack trace:
> > > >  reset_page_owner include/linux/page_owner.h:25 [inline]
> > > >  free_pages_prepare mm/page_alloc.c:1127 [inline]
> > > >  free_unref_page+0x714/0x10c0 mm/page_alloc.c:2657
> > > >  vfree+0x17e/0x890 mm/vmalloc.c:3382
> > > >  delayed_vfree_work+0x57/0x70 mm/vmalloc.c:3303
> > > >  process_one_work+0x9a2/0x1ba0 kernel/workqueue.c:3229
> > > >  process_scheduled_works kernel/workqueue.c:3310 [inline]
> > > >  worker_thread+0x677/0xe90 kernel/workqueue.c:3391
> > > >  kthread+0x2ca/0x3b0 kernel/kthread.c:389
> > > >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> > > >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> > > >
> > > > Memory state around the buggy address:
> > > >  ffff888027873f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> > > >  ffff888027873f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> > > > >ffff888027874000: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> > > >                                            ^
> > > >  ffff888027874080: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
> > > >  ffff888027874100: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
> > > > ==================================================================
> > > > We also find a similar bug report in function zswap_store(), listed as below:
> > > >
> > > > ==================================================================
> > > > BUG: KASAN: slab-use-after-free in zswap_compress mm/zswap.c:925 [inline]
> > > > BUG: KASAN: slab-use-after-free in zswap_store_page mm/zswap.c:1426 [inline]
> > > > BUG: KASAN: slab-use-after-free in zswap_store+0x2307/0x25e0 mm/zswap.c:1533
> > > > Read of size 4 at addr ffff8880219f6b44 by task kswapd0/88
> > > >
> > > > CPU: 1 UID: 0 PID: 88 Comm: kswapd0 Tainted: G     U
> > > > 6.12.0-09435-g2c22dc1ee3a1 #11
> > > > Tainted: [U]=USER
> > > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> > > > rel-1.16.1-0-g3208b098f51a-prebuilt.qemu.org 04/01/2014
> > > > Call Trace:
> > > >  <TASK>
> > > >  __dump_stack lib/dump_stack.c:94 [inline]
> > > >  dump_stack_lvl+0x116/0x1b0 lib/dump_stack.c:120
> > > >  print_address_description mm/kasan/report.c:378 [inline]
> > > >  print_report+0xc0/0x5e0 mm/kasan/report.c:489
> > > >  kasan_report+0xbd/0xf0 mm/kasan/report.c:602
> > > >  zswap_compress mm/zswap.c:925 [inline]
> > > >  zswap_store_page mm/zswap.c:1426 [inline]
> > > >  zswap_store+0x2307/0x25e0 mm/zswap.c:1533
> > > >  swap_writepage+0x3a8/0xe50 mm/page_io.c:279
> > > >  pageout+0x3b9/0xa90 mm/vmscan.c:689
> > > >  shrink_folio_list+0x2988/0x4340 mm/vmscan.c:1367
> > > >  evict_folios+0x72b/0x1a10 mm/vmscan.c:4593
> > > >  try_to_shrink_lruvec+0x62b/0xa60 mm/vmscan.c:4789
> > > >  shrink_one+0x417/0x7c0 mm/vmscan.c:4834
> > > >  shrink_many mm/vmscan.c:4897 [inline]
> > > >  lru_gen_shrink_node mm/vmscan.c:4975 [inline]
> > > >  shrink_node+0x269a/0x3d60 mm/vmscan.c:5956
> > > >  kswapd_shrink_node mm/vmscan.c:6785 [inline]
> > > >  balance_pgdat+0xbe5/0x18c0 mm/vmscan.c:6977
> > > >  kswapd+0x6ff/0xd60 mm/vmscan.c:7246
> > > >  kthread+0x2ca/0x3b0 kernel/kthread.c:389
> > > >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> > > >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> > > >  </TASK>
> > > >
> > > > Allocated by task 1:
> > > >  kasan_save_stack+0x24/0x50 mm/kasan/common.c:47
> > > >  kasan_save_track+0x14/0x30 mm/kasan/common.c:68
> > > >  poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
> > > >  __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
> > > >  kasan_kmalloc include/linux/kasan.h:260 [inline]
> > > >  __do_kmalloc_node mm/slub.c:4283 [inline]
> > > >  __kmalloc_noprof+0x212/0x530 mm/slub.c:4295
> > > >  kmalloc_noprof include/linux/slab.h:905 [inline]
> > > >  kzalloc_noprof include/linux/slab.h:1037 [inline]
> > > >  __acomp_request_alloc_noprof include/crypto/internal/acompress.h:75 [inline]
> > > >  acomp_request_alloc+0x46/0x110 crypto/acompress.c:131
> > > >  zswap_cpu_comp_prepare+0x1f4/0x470 mm/zswap.c:840
> > > >  cpuhp_invoke_callback+0x26d/0x9d0 kernel/cpu.c:204
> > > >  cpuhp_issue_call+0x1c1/0x8d0 kernel/cpu.c:2375
> > > >  __cpuhp_state_add_instance_cpuslocked+0x26a/0x3c0 kernel/cpu.c:2437
> > > >  __cpuhp_state_add_instance+0xd7/0x2e0 kernel/cpu.c:2458
> > > >  cpuhp_state_add_instance include/linux/cpuhotplug.h:386 [inline]
> > > >  zswap_pool_create+0x2c3/0x5c0 mm/zswap.c:288
> > > >  __zswap_pool_create_fallback mm/zswap.c:356 [inline]
> > > >  zswap_setup+0x3a5/0x820 mm/zswap.c:1781
> > > >  zswap_init+0x2d/0x40 mm/zswap.c:1817
> > > >  do_one_initcall+0x111/0x6d0 init/main.c:1266
> > > >  do_initcall_level init/main.c:1328 [inline]
> > > >  do_initcalls init/main.c:1344 [inline]
> > > >  do_basic_setup init/main.c:1363 [inline]
> > > >  kernel_init_freeable+0x5ae/0x8a0 init/main.c:1577
> > > >  kernel_init+0x1e/0x2d0 init/main.c:1466
> > > >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> > > >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> > > >
> > > > Freed by task 901:
> > > >  kasan_save_stack+0x24/0x50 mm/kasan/common.c:47
> > > >  kasan_save_track+0x14/0x30 mm/kasan/common.c:68
> > > >  kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:582
> > > >  poison_slab_object mm/kasan/common.c:247 [inline]
> > > >  __kasan_slab_free+0x54/0x70 mm/kasan/common.c:264
> > > >  kasan_slab_free include/linux/kasan.h:233 [inline]
> > > >  slab_free_hook mm/slub.c:2338 [inline]
> > > >  slab_free mm/slub.c:4598 [inline]
> > > >  kfree+0x14e/0x4d0 mm/slub.c:4746
> > > >  zswap_cpu_comp_dead+0xe3/0x1c0 mm/zswap.c:874
> > > >  cpuhp_invoke_callback+0x564/0x9d0 kernel/cpu.c:216
> > > >  __cpuhp_invoke_callback_range+0x104/0x220 kernel/cpu.c:965
> > > >  cpuhp_invoke_callback_range kernel/cpu.c:989 [inline]
> > > >  cpuhp_down_callbacks kernel/cpu.c:1382 [inline]
> > > >  _cpu_down+0x41d/0xef0 kernel/cpu.c:1443
> > > >  __cpu_down_maps_locked+0x6f/0x90 kernel/cpu.c:1473
> > > >  work_for_cpu_fn+0x55/0xa0 kernel/workqueue.c:6719
> > > >  process_one_work+0x9a2/0x1ba0 kernel/workqueue.c:3229
> > > >  process_scheduled_works kernel/workqueue.c:3310 [inline]
> > > >  worker_thread+0x677/0xe90 kernel/workqueue.c:3391
> > > >  kthread+0x2ca/0x3b0 kernel/kthread.c:389
> > > >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> > > >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> > > >
> > > > The buggy address belongs to the object at ffff8880219f6b00
> > > >  which belongs to the cache kmalloc-96 of size 96
> > > > The buggy address is located 68 bytes inside of
> > > >  freed 96-byte region [ffff8880219f6b00, ffff8880219f6b60)
> > > >
> > > > The buggy address belongs to the physical page:
> > > > page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x219f6
> > > > anon flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
> > > > page_type: f5(slab)
> > > > raw: 00fff00000000000 ffff88801b041280 ffffea0000887d00 dead000000000005
> > > > raw: 0000000000000000 0000000000200020 00000001f5000000 0000000000000000
> > > > page dumped because: kasan: bad access detected
> > > > page_owner tracks the page as allocated
> > > > page last allocated via order 0, migratetype Unmovable, gfp_mask
> > > > 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 1, tgid
> > > > 1 (swapper/0), ts 15792736110, free_ts 14433067061
> > > >  set_page_owner include/linux/page_owner.h:32 [inline]
> > > >  post_alloc_hook+0x2e7/0x350 mm/page_alloc.c:1556
> > > >  prep_new_page mm/page_alloc.c:1564 [inline]
> > > >  get_page_from_freelist+0xe4e/0x2b20 mm/page_alloc.c:3474
> > > >  __alloc_pages_noprof+0x219/0x21f0 mm/page_alloc.c:4751
> > > >  alloc_pages_mpol_noprof+0x2b6/0x600 mm/mempolicy.c:2265
> > > >  alloc_slab_page mm/slub.c:2408 [inline]
> > > >  allocate_slab mm/slub.c:2574 [inline]
> > > >  new_slab+0x2d5/0x420 mm/slub.c:2627
> > > >  ___slab_alloc+0xbb7/0x1850 mm/slub.c:3815
> > > >  __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3905
> > > >  __slab_alloc_node mm/slub.c:3980 [inline]
> > > >  slab_alloc_node mm/slub.c:4141 [inline]
> > > >  __kmalloc_cache_noprof+0x280/0x410 mm/slub.c:4309
> > > >  kmalloc_noprof include/linux/slab.h:901 [inline]
> > > >  kzalloc_noprof include/linux/slab.h:1037 [inline]
> > > >  usb_hub_create_port_device+0xbb/0xde0 drivers/usb/core/port.c:743
> > > >  hub_configure drivers/usb/core/hub.c:1710 [inline]
> > > >  hub_probe+0x1ceb/0x2fc0 drivers/usb/core/hub.c:1965
> > > >  usb_probe_interface+0x314/0x9f0 drivers/usb/core/driver.c:399
> > > >  call_driver_probe drivers/base/dd.c:579 [inline]
> > > >  really_probe+0x252/0xa90 drivers/base/dd.c:658
> > > >  __driver_probe_device+0x1df/0x450 drivers/base/dd.c:800
> > > >  driver_probe_device+0x4c/0x1a0 drivers/base/dd.c:830
> > > >  __device_attach_driver+0x1db/0x2f0 drivers/base/dd.c:958
> > > >  bus_for_each_drv+0x14c/0x1d0 drivers/base/bus.c:459
> > > > page last free pid 25 tgid 25 stack trace:
> > > >  reset_page_owner include/linux/page_owner.h:25 [inline]
> > > >  free_pages_prepare mm/page_alloc.c:1127 [inline]
> > > >  free_unref_page+0x714/0x10c0 mm/page_alloc.c:2657
> > > >  vfree+0x17e/0x890 mm/vmalloc.c:3382
> > > >  delayed_vfree_work+0x57/0x70 mm/vmalloc.c:3303
> > > >  process_one_work+0x9a2/0x1ba0 kernel/workqueue.c:3229
> > > >  process_scheduled_works kernel/workqueue.c:3310 [inline]
> > > >  worker_thread+0x677/0xe90 kernel/workqueue.c:3391
> > > >  kthread+0x2ca/0x3b0 kernel/kthread.c:389
> > > >  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
> > > >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> > > >
> > > > Memory state around the buggy address:
> > > >  ffff8880219f6a00: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
> > > >  ffff8880219f6a80: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
> > > > >ffff8880219f6b00: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> > > >                                            ^
> > > >  ffff8880219f6b80: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
> > > >  ffff8880219f6c00: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> > > > ==================================================================
> > > > If you have any questions, please contact us.
> > > >
> > > > Best Regards,
> > > > Yue