Re: [syzbot] [media?] KASAN: slab-use-after-free Read in dvb_device_open

[syzbot <syzbot+1eb177ecc3943b883f0a@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-use-after-free Read in dvb_device_open

==================================================================
BUG: KASAN: slab-use-after-free in dvb_device_open+0x405/0x470 drivers/media/dvb-core/dvbdev.c:99
Read of size 8 at addr ffff888143aaf018 by task syz.3.546/8305

CPU: 0 UID: 0 PID: 8305 Comm: syz.3.546 Not tainted 6.12.0-syzkaller-10299-gae5cd00f92cb #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xc3/0x620 mm/kasan/report.c:489
 kasan_report+0xd9/0x110 mm/kasan/report.c:602
 dvb_device_open+0x405/0x470 drivers/media/dvb-core/dvbdev.c:99
 chrdev_open+0x237/0x6a0 fs/char_dev.c:414
 do_dentry_open+0xf59/0x1ea0 fs/open.c:945
 vfs_open+0x82/0x3f0 fs/open.c:1075
 do_open fs/namei.c:3828 [inline]
 path_openat+0x1e6a/0x2d60 fs/namei.c:3987
 do_filp_open+0x20c/0x470 fs/namei.c:4014
 do_sys_openat2+0x17a/0x1e0 fs/open.c:1402
 do_sys_open fs/open.c:1417 [inline]
 __do_sys_openat fs/open.c:1433 [inline]
 __se_sys_openat fs/open.c:1428 [inline]
 __x64_sys_openat+0x175/0x210 fs/open.c:1428
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9a46d85d29
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f9a47b85038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f9a46f75fa0 RCX: 00007f9a46d85d29
RDX: 0000000000000001 RSI: 0000000020000000 RDI: ffffffffffffff9c
RBP: 00007f9a46e01b08 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f9a46f75fa0 R15: 00007ffe1e4113f8
 </TASK>

Allocated by task 1:
 kasan_save_stack+0x33/0x60 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
 kmalloc_noprof include/linux/slab.h:901 [inline]
 kzalloc_noprof include/linux/slab.h:1037 [inline]
 dvb_register_device+0x1e2/0x2380 drivers/media/dvb-core/dvbdev.c:479
 dvb_register_frontend+0x5a7/0x880 drivers/media/dvb-core/dvb_frontend.c:3051
 vidtv_bridge_dvb_init drivers/media/test-drivers/vidtv/vidtv_bridge.c:430 [inline]
 vidtv_bridge_probe+0x45e/0xa90 drivers/media/test-drivers/vidtv/vidtv_bridge.c:502
 platform_probe+0xff/0x1f0 drivers/base/platform.c:1404
 call_driver_probe drivers/base/dd.c:579 [inline]
 really_probe+0x23e/0xa90 drivers/base/dd.c:658
 __driver_probe_device+0x1de/0x440 drivers/base/dd.c:800
 driver_probe_device+0x4c/0x1b0 drivers/base/dd.c:830
 __driver_attach+0x283/0x580 drivers/base/dd.c:1216
 bus_for_each_dev+0x13c/0x1d0 drivers/base/bus.c:370
 bus_add_driver+0x2e9/0x690 drivers/base/bus.c:675
 driver_register+0x15c/0x4b0 drivers/base/driver.c:246
 vidtv_bridge_init+0x45/0x80 drivers/media/test-drivers/vidtv/vidtv_bridge.c:592
 do_one_initcall+0x128/0x630 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+0x58f/0x8b0 init/main.c:1577
 kernel_init+0x1c/0x2b0 init/main.c:1466
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Freed by task 8297:
 kasan_save_stack+0x33/0x60 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+0x51/0x70 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+0x14f/0x4b0 mm/slub.c:4746
 dvb_free_device drivers/media/dvb-core/dvbdev.c:623 [inline]
 kref_put include/linux/kref.h:65 [inline]
 dvb_device_put.part.0+0x60/0x90 drivers/media/dvb-core/dvbdev.c:636
 dvb_device_put drivers/media/dvb-core/dvbdev.c:635 [inline]
 dvb_device_open+0x374/0x470 drivers/media/dvb-core/dvbdev.c:117
 chrdev_open+0x237/0x6a0 fs/char_dev.c:414
 do_dentry_open+0xf59/0x1ea0 fs/open.c:945
 vfs_open+0x82/0x3f0 fs/open.c:1075
 do_open fs/namei.c:3828 [inline]
 path_openat+0x1e6a/0x2d60 fs/namei.c:3987
 do_filp_open+0x20c/0x470 fs/namei.c:4014
 do_sys_openat2+0x17a/0x1e0 fs/open.c:1402
 do_sys_open fs/open.c:1417 [inline]
 __do_sys_openat fs/open.c:1433 [inline]
 __se_sys_openat fs/open.c:1428 [inline]
 __x64_sys_openat+0x175/0x210 fs/open.c:1428
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888143aaf000
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 24 bytes inside of
 freed 256-byte region [ffff888143aaf000, ffff888143aaf100)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x143aae
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x57ff00000000040(head|node=1|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 057ff00000000040 ffff88801ac41b40 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000100010 00000001f5000000 0000000000000000
head: 057ff00000000040 ffff88801ac41b40 dead000000000122 0000000000000000
head: 0000000000000000 0000000000100010 00000001f5000000 0000000000000000
head: 057ff00000000001 ffffea00050eab81 ffffffffffffffff 0000000000000000
head: 0000000000000002 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 14768145455, free_ts 0
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x2d1/0x350 mm/page_alloc.c:1556
 prep_new_page mm/page_alloc.c:1564 [inline]
 get_page_from_freelist+0xfce/0x2f80 mm/page_alloc.c:3474
 __alloc_pages_noprof+0x223/0x25a0 mm/page_alloc.c:4751
 alloc_pages_mpol_noprof+0x2c9/0x610 mm/mempolicy.c:2265
 alloc_slab_page mm/slub.c:2408 [inline]
 allocate_slab mm/slub.c:2574 [inline]
 new_slab+0x2c9/0x410 mm/slub.c:2627
 ___slab_alloc+0xd1d/0x16e0 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+0xf6/0x420 mm/slub.c:4309
 kmalloc_noprof include/linux/slab.h:901 [inline]
 kzalloc_noprof include/linux/slab.h:1037 [inline]
 bus_add_driver+0x92/0x690 drivers/base/bus.c:659
 driver_register+0x15c/0x4b0 drivers/base/driver.c:246
 usb_register_driver+0x24a/0x500 drivers/usb/core/driver.c:1082
 uvc_init+0x24/0x60 drivers/media/usb/uvc/uvc_driver.c:3170
 do_one_initcall+0x128/0x630 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+0x58f/0x8b0 init/main.c:1577
 kernel_init+0x1c/0x2b0 init/main.c:1466
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888143aaef00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888143aaef80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888143aaf000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff888143aaf080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888143aaf100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


Tested on:

commit:         ae5cd00f dvb: prevent double free dvb device
git tree:       https://github.com/ea1davis/linux mdbc/syz
console output: https://syzkaller.appspot.com/x/log.txt?x=163d91f8580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e8d97faf7b870c89
dashboard link: https://syzkaller.appspot.com/bug?extid=1eb177ecc3943b883f0a
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.