Re: [syzbot] [media?] [usb?] KASAN: slab-use-after-free Read in v4l2_open

public inbox for linux-kernel@vger.kernel.org
 help / color / mirror / Atom feed

From: syzbot <syzbot+1a7507a194fff09e5c44@syzkaller.appspotmail.com>
To: kartikey406@gmail.com, linux-kernel@vger.kernel.org,
	 syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] [media?] [usb?] KASAN: slab-use-after-free Read in v4l2_open
Date: Fri, 20 Mar 2026 04:05:01 -0700	[thread overview]
Message-ID: <69bd29dd.050a0220.3bf4de.001e.GAE@google.com> (raw)
In-Reply-To: <20260320062304.1097949-1-kartikey406@gmail.com>

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-use-after-free Read in v4l2_open

==================================================================
BUG: KASAN: slab-use-after-free in v4l2_open+0x395/0x3a0 drivers/media/v4l2-core/v4l2-dev.c:444
Read of size 4 at addr ffff88801b71c858 by task v4l_id/6825

CPU: 1 UID: 0 PID: 6825 Comm: v4l_id Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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
 v4l2_open+0x395/0x3a0 drivers/media/v4l2-core/v4l2-dev.c:444
 chrdev_open+0x4cd/0x5e0 fs/char_dev.c:411
 do_dentry_open+0x785/0x14e0 fs/open.c:949
 vfs_open+0x3b/0x340 fs/open.c:1081
 do_open fs/namei.c:4693 [inline]
 path_openat+0x2e08/0x3860 fs/namei.c:4852
 do_file_open+0x23e/0x4a0 fs/namei.c:4881
 do_sys_openat2+0x113/0x200 fs/open.c:1366
 do_sys_open fs/open.c:1372 [inline]
 __do_sys_openat fs/open.c:1388 [inline]
 __se_sys_openat fs/open.c:1383 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1383
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f85abca7407
Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007ffeda7065e0 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f85ac45c880 RCX: 00007f85abca7407
RDX: 0000000000000000 RSI: 00007ffeda706f1c RDI: ffffffffffffff9c
RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 00007ffeda706830 R14: 00007f85ac5c3000 R15: 000056264efca4d8
 </TASK>

Allocated by task 6729:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __kmalloc_cache_noprof+0x31c/0x660 mm/slub.c:5412
 kmalloc_noprof include/linux/slab.h:950 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 em28xx_v4l2_init+0x10c/0x2ff0 drivers/media/usb/em28xx/em28xx-video.c:2538
 em28xx_init_extension+0x120/0x1c0 drivers/media/usb/em28xx/em28xx-core.c:1117
 process_one_work+0x9a3/0x1710 kernel/workqueue.c:3288
 process_scheduled_works kernel/workqueue.c:3379 [inline]
 worker_thread+0xba8/0x11e0 kernel/workqueue.c:3465
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 6729:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x46/0x50 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:2689 [inline]
 slab_free mm/slub.c:6242 [inline]
 kfree+0x1c5/0x640 mm/slub.c:6557
 em28xx_free_v4l2 drivers/media/usb/em28xx/em28xx-video.c:2118 [inline]
 kref_put include/linux/kref.h:65 [inline]
 em28xx_v4l2_init+0x16c8/0x2ff0 drivers/media/usb/em28xx/em28xx-video.c:2907
 em28xx_init_extension+0x120/0x1c0 drivers/media/usb/em28xx/em28xx-core.c:1117
 process_one_work+0x9a3/0x1710 kernel/workqueue.c:3288
 process_scheduled_works kernel/workqueue.c:3379 [inline]
 worker_thread+0xba8/0x11e0 kernel/workqueue.c:3465
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x51e/0xb90 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 ffff88801b71c000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 2136 bytes inside of
 freed 8192-byte region [ffff88801b71c000, ffff88801b71e000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1b718
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801b042280 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800020002 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b042280 dead000000000100 dead000000000122
head: 0000000000000000 0000000800020002 00000000f5000000 0000000000000000
head: 00fff00000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd28c0(GFP_NOWAIT|__GFP_IO|__GFP_FS|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5958, tgid 5958 (syz-executor), ts 82175242574, free_ts 82087244705
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x231/0x280 mm/page_alloc.c:1857
 prep_new_page mm/page_alloc.c:1865 [inline]
 get_page_from_freelist+0x2418/0x24b0 mm/page_alloc.c:3924
 __alloc_frozen_pages_noprof+0x233/0x3d0 mm/page_alloc.c:5211
 alloc_slab_page mm/slub.c:3278 [inline]
 allocate_slab+0x77/0x660 mm/slub.c:3467
 new_slab mm/slub.c:3525 [inline]
 refill_objects+0x339/0x3d0 mm/slub.c:7247
 refill_sheaf mm/slub.c:2816 [inline]
 __pcs_replace_empty_main+0x321/0x720 mm/slub.c:4651
 alloc_from_pcs mm/slub.c:4749 [inline]
 slab_alloc_node mm/slub.c:4883 [inline]
 __do_kmalloc_node mm/slub.c:5291 [inline]
 __kvmalloc_node_noprof+0x657/0x8a0 mm/slub.c:6824
 kvmalloc_array_node_noprof include/linux/slab.h:1216 [inline]
 __ptr_ring_init_queue_alloc_noprof include/linux/ptr_ring.h:481 [inline]
 ptr_ring_resize_noprof include/linux/ptr_ring.h:601 [inline]
 tun_attach+0x891/0x1590 drivers/net/tun.c:727
 tun_net_init+0x309/0x3d0 drivers/net/tun.c:940
 register_netdevice+0x6d1/0x1cf0 net/core/dev.c:11367
 tun_set_iff+0x844/0xf00 drivers/net/tun.c:2807
 __tun_chr_ioctl+0x7c8/0x1e30 drivers/net/tun.c:3088
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5958 tgid 5958 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1401 [inline]
 __free_frozen_pages+0xbf0/0xd00 mm/page_alloc.c:2942
 __slab_free+0x274/0x2c0 mm/slub.c:5605
 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:4569 [inline]
 slab_alloc_node mm/slub.c:4898 [inline]
 __kmalloc_cache_noprof+0x2ba/0x660 mm/slub.c:5407
 kmalloc_noprof include/linux/slab.h:950 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 inet_alloc_ifa net/ipv4/devinet.c:212 [inline]
 inet_rtm_to_ifa net/ipv4/devinet.c:904 [inline]
 inet_rtm_newaddr+0x5d8/0x1ad0 net/ipv4/devinet.c:980
 rtnetlink_rcv_msg+0x7d5/0xbe0 net/core/rtnetlink.c:6958
 netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x80f/0x9b0 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec+0x112/0x150 net/socket.c:796
 __sock_sendmsg net/socket.c:811 [inline]
 __sys_sendto+0x3ff/0x590 net/socket.c:2279
 __do_sys_sendto net/socket.c:2286 [inline]
 __se_sys_sendto net/socket.c:2282 [inline]
 __x64_sys_sendto+0xde/0x100 net/socket.c:2282
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88801b71c700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88801b71c780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88801b71c800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                    ^
 ffff88801b71c880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88801b71c900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


Tested on:

commit:         b5d083a3 Add linux-next specific files for 20260319
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=11a8f2da580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9e197b084b913f8d
dashboard link: https://syzkaller.appspot.com/bug?extid=1a7507a194fff09e5c44
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1013cada580000

next      parent reply	other threads:[~2026-03-20 11:05 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20260320062304.1097949-1-kartikey406@gmail.com>
2026-03-20 11:05 ` syzbot [this message]
     [not found] <20260319124025.1093288-1-kartikey406@gmail.com>
2026-03-20  5:44 ` [syzbot] [media?] [usb?] KASAN: slab-use-after-free Read in v4l2_open syzbot
2026-03-19  7:21 syzbot
2026-03-19  9:00 ` Edward Adam Davis
2026-03-19  9:29   ` syzbot
2026-03-19 12:20 ` Edward Adam Davis
2026-03-20  5:31   ` syzbot
2026-03-19 16:45 ` Edward Adam Davis
2026-03-20 10:30   ` syzbot

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=69bd29dd.050a0220.3bf4de.001e.GAE@google.com \
    --to=syzbot+1a7507a194fff09e5c44@syzkaller.appspotmail.com \
    --cc=kartikey406@gmail.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=syzkaller-bugs@googlegroups.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Be sure your reply has a Subject: header at the top and a blank line before the message body.

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox