[syzbot] [usb?] KASAN: slab-use-after-free Read in stub_rx_loop

[syzbot] [usb?] KASAN: slab-use-after-free Read in stub_rx_loop

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    48a5a7ab8d6a Merge tag 'v7.2-rc4-smb3-client-fixes' of git..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=113c32ea580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=20c9876b0f77b546
dashboard link: https://syzkaller.appspot.com/bug?extid=06fa667a0931a3430026
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-48a5a7ab.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cca5551ec121/vmlinux-48a5a7ab.xz
kernel image: https://storage.googleapis.com/syzbot-assets/30b6e710a3ae/bzImage-48a5a7ab.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+06fa667a0931a3430026@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in stub_recv_cmd_submit drivers/usb/usbip/stub_rx.c:609 [inline]
BUG: KASAN: slab-use-after-free in stub_rx_pdu drivers/usb/usbip/stub_rx.c:688 [inline]
BUG: KASAN: slab-use-after-free in stub_rx_loop+0x2965/0x2ee0 drivers/usb/usbip/stub_rx.c:707
Read of size 4 at addr ffff888012cacdb0 by task stub_rx/5324

CPU: 0 UID: 0 PID: 5324 Comm: stub_rx Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description+0x55/0x1e0 mm/kasan/report.c:378
 print_report+0x58/0x70 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 stub_recv_cmd_submit drivers/usb/usbip/stub_rx.c:609 [inline]
 stub_rx_pdu drivers/usb/usbip/stub_rx.c:688 [inline]
 stub_rx_loop+0x2965/0x2ee0 drivers/usb/usbip/stub_rx.c:707
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 5324:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 unpoison_slab_object mm/kasan/common.c:340 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4612 [inline]
 slab_alloc_node mm/slub.c:4945 [inline]
 kmem_cache_alloc_noprof+0x2a0/0x5f0 mm/slub.c:4959
 stub_priv_alloc drivers/usb/usbip/stub_rx.c:314 [inline]
 stub_recv_cmd_submit drivers/usb/usbip/stub_rx.c:490 [inline]
 stub_rx_pdu drivers/usb/usbip/stub_rx.c:688 [inline]
 stub_rx_loop+0xad9/0x2ee0 drivers/usb/usbip/stub_rx.c:707
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 5325:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2705 [inline]
 slab_free mm/slub.c:6405 [inline]
 kmem_cache_free+0x182/0x650 mm/slub.c:6532
 stub_send_ret_submit drivers/usb/usbip/stub_tx.c:333 [inline]
 stub_tx_loop+0x1b16/0x2800 drivers/usb/usbip/stub_tx.c:437
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

The buggy address belongs to the object at ffff888012cacd80
 which belongs to the cache stub_priv of size 64
The buggy address is located 48 bytes inside of
 freed 64-byte region [ffff888012cacd80, ffff888012cacdc0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff888012cace00 pfn:0x12cac
flags: 0xfff00000000200(workingset|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000200 ffff888033fd4280 ffff8880340e27c8 ffff8880340e27c8
raw: ffff888012cace00 000000080020001c 00000000f5000000 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 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5324, tgid 5324 (stub_rx), ts 94362120884, free_ts 93984048542
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1859
 prep_new_page mm/page_alloc.c:1867 [inline]
 get_page_from_freelist+0x21fa/0x2270 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5304
 alloc_slab_page mm/slub.c:3294 [inline]
 allocate_slab+0x79/0x5e0 mm/slub.c:3408
 new_slab mm/slub.c:3454 [inline]
 refill_objects+0x2d5/0x350 mm/slub.c:7338
 refill_sheaf mm/slub.c:2832 [inline]
 __pcs_replace_empty_main+0x2bf/0x6b0 mm/slub.c:4703
 alloc_from_pcs mm/slub.c:4801 [inline]
 slab_alloc_node mm/slub.c:4933 [inline]
 kmem_cache_alloc_noprof+0x382/0x5f0 mm/slub.c:4959
 stub_priv_alloc drivers/usb/usbip/stub_rx.c:314 [inline]
 stub_recv_cmd_submit drivers/usb/usbip/stub_rx.c:490 [inline]
 stub_rx_pdu drivers/usb/usbip/stub_rx.c:688 [inline]
 stub_rx_loop+0xad9/0x2ee0 drivers/usb/usbip/stub_rx.c:707
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
page last free pid 4993 tgid 4993 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1406 [inline]
 __free_frozen_pages+0xc1e/0xd10 mm/page_alloc.c:2950
 __slab_free+0x274/0x2c0 mm/slub.c:5767
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x99/0x100 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:350
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4612 [inline]
 slab_alloc_node mm/slub.c:4945 [inline]
 kmem_cache_alloc_node_noprof+0x355/0x610 mm/slub.c:5017
 __alloc_skb+0x1d7/0x7a0 net/core/skbuff.c:704
 alloc_skb include/linux/skbuff.h:1384 [inline]
 alloc_skb_with_frags+0xc6/0x760 net/core/skbuff.c:6769
 sock_alloc_send_pskb+0x878/0x990 net/core/sock.c:3013
 unix_dgram_sendmsg+0x4fe/0x1870 net/unix/af_unix.c:2136
 sock_sendmsg_nosec+0x13a/0x180 net/socket.c:775
 __sock_sendmsg net/socket.c:790 [inline]
 sock_write_iter+0x2de/0x3e0 net/socket.c:1241
 do_iter_readv_writev+0x612/0x8c0 fs/read_write.c:-1
 vfs_writev+0x343/0x990 fs/read_write.c:1058
 do_writev+0x154/0x2e0 fs/read_write.c:1104
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94

Memory state around the buggy address:
 ffff888012cacc80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888012cacd00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888012cacd80: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
                                     ^
 ffff888012cace00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888012cace80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


---
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#syz undup

Re: [syzbot] [usb?] KASAN: slab-use-after-free Read in stub_rx_loop

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    818bebeb63dd drm/xe: Don't hand out the flat CCS storage a..
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=151ce979580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ccca94d2c01b9e78
dashboard link: https://syzkaller.appspot.com/bug?extid=06fa667a0931a3430026
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13a28d49580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+06fa667a0931a3430026@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in stub_recv_cmd_submit drivers/usb/usbip/stub_rx.c:609 [inline]
BUG: KASAN: slab-use-after-free in stub_rx_pdu drivers/usb/usbip/stub_rx.c:688 [inline]
BUG: KASAN: slab-use-after-free in stub_rx_loop+0x2d3b/0x31c0 drivers/usb/usbip/stub_rx.c:707
Read of size 4 at addr ffff888034999db0 by task stub_rx/6028

CPU: 0 UID: 0 PID: 6028 Comm: stub_rx Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x13d/0x4b0 mm/kasan/report.c:482
 kasan_report+0xdf/0x1c0 mm/kasan/report.c:595
 stub_recv_cmd_submit drivers/usb/usbip/stub_rx.c:609 [inline]
 stub_rx_pdu drivers/usb/usbip/stub_rx.c:688 [inline]
 stub_rx_loop+0x2d3b/0x31c0 drivers/usb/usbip/stub_rx.c:707
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 6028:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 unpoison_slab_object mm/kasan/common.c:340 [inline]
 __kasan_slab_alloc+0x89/0x90 mm/kasan/common.c:366
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4586 [inline]
 slab_alloc_node mm/slub.c:4919 [inline]
 kmem_cache_alloc_noprof+0x26b/0x6a0 mm/slub.c:4933
 stub_priv_alloc drivers/usb/usbip/stub_rx.c:314 [inline]
 stub_recv_cmd_submit drivers/usb/usbip/stub_rx.c:490 [inline]
 stub_rx_pdu drivers/usb/usbip/stub_rx.c:688 [inline]
 stub_rx_loop+0x638/0x31c0 drivers/usb/usbip/stub_rx.c:707
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 6029:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2678 [inline]
 slab_free mm/slub.c:6372 [inline]
 kmem_cache_free+0x127/0x6b0 mm/slub.c:6499
 stub_free_priv_and_urb+0x427/0x570 drivers/usb/usbip/stub_main.c:321
 stub_send_ret_submit+0xecf/0x1810 drivers/usb/usbip/stub_tx.c:333
 stub_tx_loop+0xe2/0x3e0 drivers/usb/usbip/stub_tx.c:437
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

The buggy address belongs to the object at ffff888034999d80
 which belongs to the cache stub_priv of size 64
The buggy address is located 48 bytes inside of
 freed 64-byte region [ffff888034999d80, ffff888034999dc0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff888034999e00 pfn:0x34999
flags: 0xfff00000000200(workingset|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000200 ffff8881016c7540 ffff88802aafa948 ffff88802aafa948
raw: ffff888034999e00 000000080020001c 00000000f5000000 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 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 6028, tgid 6028 (stub_rx), ts 78215496489
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1871
 prep_new_page mm/page_alloc.c:1879 [inline]
 get_page_from_freelist+0x110d/0x35b0 mm/page_alloc.c:3943
 __alloc_frozen_pages_noprof+0x2eb/0x3300 mm/page_alloc.c:5436
 alloc_slab_page mm/slub.c:3267 [inline]
 allocate_slab mm/slub.c:3382 [inline]
 new_slab+0xa5/0x640 mm/slub.c:3428
 refill_objects+0xe3/0x410 mm/slub.c:7305
 refill_sheaf mm/slub.c:2805 [inline]
 __pcs_replace_empty_main+0x372/0x680 mm/slub.c:4677
 alloc_from_pcs mm/slub.c:4775 [inline]
 slab_alloc_node mm/slub.c:4907 [inline]
 kmem_cache_alloc_noprof+0x46e/0x6a0 mm/slub.c:4933
 stub_priv_alloc drivers/usb/usbip/stub_rx.c:314 [inline]
 stub_recv_cmd_submit drivers/usb/usbip/stub_rx.c:490 [inline]
 stub_rx_pdu drivers/usb/usbip/stub_rx.c:688 [inline]
 stub_rx_loop+0x638/0x31c0 drivers/usb/usbip/stub_rx.c:707
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
page last free pid 15 tgid 15 ts 77527058318 stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 __free_pages_prepare mm/page_alloc.c:1418 [inline]
 __free_frozen_pages+0x79f/0x10f0 mm/page_alloc.c:2962
 __pagetable_free include/linux/mm.h:3745 [inline]
 pagetable_free include/linux/mm.h:3769 [inline]
 pagetable_dtor_free include/linux/mm.h:3868 [inline]
 __tlb_remove_table include/asm-generic/tlb.h:221 [inline]
 __tlb_remove_table_free mm/mmu_gather.c:228 [inline]
 tlb_remove_table_rcu+0x2cf/0x380 mm/mmu_gather.c:291
 rcu_do_batch kernel/rcu/tree.c:2645 [inline]
 rcu_core+0x5a2/0x10e0 kernel/rcu/tree.c:2897
 handle_softirqs+0x1e6/0x9d0 kernel/softirq.c:645
 __do_softirq kernel/softirq.c:679 [inline]
 invoke_softirq kernel/softirq.c:519 [inline]
 __irq_exit_rcu+0x194/0x210 kernel/softirq.c:767
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:784
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
 sysvec_apic_timer_interrupt+0xa3/0xc0 arch/x86/kernel/apic/apic.c:1062
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674

Memory state around the buggy address:
 ffff888034999c80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888034999d00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888034999d80: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
                                     ^
 ffff888034999e00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888034999e80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

[PATCH] usbip: prevent priv from uaf in cmd submit

[Edward Adam Davis]

The num_urbs is 1, and the request is not special, so it is not tweaked.
After stub_complete() executes, priv is added to the tx queue.
stub_tx_loop() immediately dequeues it and frees priv; the subsequent
loop iteration then checks priv->num_urbs, which ultimately triggers [1].

Use num_urbs directly to avoid accessing the already-freed priv.

[1]
BUG: KASAN: slab-use-after-free in stub_recv_cmd_submit drivers/usb/usbip/stub_rx.c:609 [inline]
Read of size 4 at addr ffff888034999db0 by task stub_rx/6028
Call Trace:
 stub_recv_cmd_submit drivers/usb/usbip/stub_rx.c:609 [inline]
 stub_rx_pdu drivers/usb/usbip/stub_rx.c:688 [inline]
 stub_rx_loop+0x2d3b/0x31c0 drivers/usb/usbip/stub_rx.c:707

Allocated by task 6028:
 stub_priv_alloc drivers/usb/usbip/stub_rx.c:314 [inline]
 stub_recv_cmd_submit drivers/usb/usbip/stub_rx.c:490 [inline]
 stub_rx_pdu drivers/usb/usbip/stub_rx.c:688 [inline]
 stub_rx_loop+0x638/0x31c0 drivers/usb/usbip/stub_rx.c:707

Freed by task 6029:
 stub_free_priv_and_urb+0x427/0x570 drivers/usb/usbip/stub_main.c:321
 stub_send_ret_submit+0xecf/0x1810 drivers/usb/usbip/stub_tx.c:333
 stub_tx_loop+0xe2/0x3e0 drivers/usb/usbip/stub_tx.c:437

Fixes: ea44d190764b ("usbip: Implement SG support to vhci-hcd and stub driver")
Reported-by: syzbot+06fa667a0931a3430026@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=06fa667a0931a3430026
Signed-off-by: Edward Adam Davis <eadavis@sina.com>
---
 drivers/usb/usbip/stub_rx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/usbip/stub_rx.c b/drivers/usb/usbip/stub_rx.c
index 1e9ae578810d..85370b3bc600 100644
--- a/drivers/usb/usbip/stub_rx.c
+++ b/drivers/usb/usbip/stub_rx.c
@@ -606,7 +606,7 @@ static void stub_recv_cmd_submit(struct stub_device *sdev,
 		return;
 
 	/* urb is now ready to submit */
-	for (i = 0; i < priv->num_urbs; i++) {
+	for (i = 0; i < num_urbs; i++) {
 		if (!is_tweaked) {
 			ret = usb_submit_urb(priv->urbs[i], GFP_KERNEL);
 
-- 
2.43.0