KASAN: use-after-free Read in v4l2_fh_open

KASAN: use-after-free Read in v4l2_fh_open

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    291009f6 Merge tag 'pm-5.11-rc8' of git://git.kernel.org/p..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17260814d00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6a218c95bd23063a
dashboard link: https://syzkaller.appspot.com/bug?extid=b2391895514ed9ef4a8e
compiler:       Debian clang version 11.0.1-2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14ec5814d00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17179dd4d00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b2391895514ed9ef4a8e@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in v4l2_fh_init drivers/media/v4l2-core/v4l2-fh.c:25 [inline]
BUG: KASAN: use-after-free in v4l2_fh_open+0xc7/0x430 drivers/media/v4l2-core/v4l2-fh.c:63
Read of size 8 at addr ffff8880228b88b8 by task v4l_id/18349

CPU: 1 PID: 18349 Comm: v4l_id Not tainted 5.11.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x137/0x1be lib/dump_stack.c:120
 print_address_description+0x5f/0x3a0 mm/kasan/report.c:230
 __kasan_report mm/kasan/report.c:396 [inline]
 kasan_report+0x15e/0x200 mm/kasan/report.c:413
 v4l2_fh_init drivers/media/v4l2-core/v4l2-fh.c:25 [inline]
 v4l2_fh_open+0xc7/0x430 drivers/media/v4l2-core/v4l2-fh.c:63
 em28xx_v4l2_open+0x15c/0xa60 drivers/media/usb/em28xx/em28xx-video.c:2163
 v4l2_open+0x229/0x360 drivers/media/v4l2-core/v4l2-dev.c:423
 chrdev_open+0x4a0/0x570 fs/char_dev.c:414
 do_dentry_open+0x7cb/0x1010 fs/open.c:817
 do_open fs/namei.c:3254 [inline]
 path_openat+0x2791/0x37a0 fs/namei.c:3371
 do_filp_open+0x191/0x3a0 fs/namei.c:3398
 do_sys_openat2+0xba/0x380 fs/open.c:1172
 do_sys_open fs/open.c:1188 [inline]
 __do_sys_open fs/open.c:1196 [inline]
 __se_sys_open fs/open.c:1192 [inline]
 __x64_sys_open+0x1af/0x1e0 fs/open.c:1192
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7fdd62b00840
Code: 73 01 c3 48 8b 0d 68 77 20 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d 89 bb 20 00 00 75 10 b8 02 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 1e f6 ff ff 48 89 04 24
RSP: 002b:00007ffe8bb255b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00007ffe8bb25728 RCX: 00007fdd62b00840
RDX: 00007fdd62aecea0 RSI: 0000000000000000 RDI: 00007ffe8bb26f1c
RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 000055f8a7dee8d0
R13: 00007ffe8bb25720 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the page:
page:00000000b7dd9778 refcount:0 mapcount:-128 mapping:0000000000000000 index:0x0 pfn:0x228b8
flags: 0xfff00000000000()
raw: 00fff00000000000 ffffea0000580108 ffff88813fffb910 0000000000000000
raw: 0000000000000000 0000000000000002 00000000ffffff7f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880228b8780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880228b8800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8880228b8880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                        ^
 ffff8880228b8900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880228b8980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

Re: KASAN: use-after-free Read in v4l2_fh_open

[SyzScope]

Hi,

This is SyzScope, a research project that aims to reveal high-risk 
primitives from a seemingly low-risk bug (UAF/OOB read, WARNING, BUG, etc.).

We are currently testing seemingly low-risk bugs on syzbot's open 
section(https://syzkaller.appspot.com/upstream), and try to reach out to 
kernel developers as long as SyzScope discovers any high-risk primitives.

Please let us know if SyzScope indeed helps, and any suggestions/feedback.

Regrading the bug "KASAN: use-after-free Read in v4l2_fh_open", SyzScope 
reports 1 memory write capability.

The detailed comments can be found at 
https://sites.google.com/view/syzscope/kasan-use-after-free-read-in-v4l2_fh_open

On 2/15/2021 7:18 AM, syzbot wrote:

> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    291009f6 Merge tag 'pm-5.11-rc8' of git://git.kernel.org/p..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=17260814d00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=6a218c95bd23063a
> dashboard link: https://syzkaller.appspot.com/bug?extid=b2391895514ed9ef4a8e
> compiler:       Debian clang version 11.0.1-2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14ec5814d00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17179dd4d00000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+b2391895514ed9ef4a8e@syzkaller.appspotmail.com
>
> ==================================================================
> BUG: KASAN: use-after-free in v4l2_fh_init drivers/media/v4l2-core/v4l2-fh.c:25 [inline]
> BUG: KASAN: use-after-free in v4l2_fh_open+0xc7/0x430 drivers/media/v4l2-core/v4l2-fh.c:63
> Read of size 8 at addr ffff8880228b88b8 by task v4l_id/18349
>
> CPU: 1 PID: 18349 Comm: v4l_id Not tainted 5.11.0-rc7-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>   __dump_stack lib/dump_stack.c:79 [inline]
>   dump_stack+0x137/0x1be lib/dump_stack.c:120
>   print_address_description+0x5f/0x3a0 mm/kasan/report.c:230
>   __kasan_report mm/kasan/report.c:396 [inline]
>   kasan_report+0x15e/0x200 mm/kasan/report.c:413
>   v4l2_fh_init drivers/media/v4l2-core/v4l2-fh.c:25 [inline]
>   v4l2_fh_open+0xc7/0x430 drivers/media/v4l2-core/v4l2-fh.c:63
>   em28xx_v4l2_open+0x15c/0xa60 drivers/media/usb/em28xx/em28xx-video.c:2163
>   v4l2_open+0x229/0x360 drivers/media/v4l2-core/v4l2-dev.c:423
>   chrdev_open+0x4a0/0x570 fs/char_dev.c:414
>   do_dentry_open+0x7cb/0x1010 fs/open.c:817
>   do_open fs/namei.c:3254 [inline]
>   path_openat+0x2791/0x37a0 fs/namei.c:3371
>   do_filp_open+0x191/0x3a0 fs/namei.c:3398
>   do_sys_openat2+0xba/0x380 fs/open.c:1172
>   do_sys_open fs/open.c:1188 [inline]
>   __do_sys_open fs/open.c:1196 [inline]
>   __se_sys_open fs/open.c:1192 [inline]
>   __x64_sys_open+0x1af/0x1e0 fs/open.c:1192
>   do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>   entry_SYSCALL_64_after_hwframe+0x44/0xa9
> RIP: 0033:0x7fdd62b00840
> Code: 73 01 c3 48 8b 0d 68 77 20 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d 89 bb 20 00 00 75 10 b8 02 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 1e f6 ff ff 48 89 04 24
> RSP: 002b:00007ffe8bb255b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
> RAX: ffffffffffffffda RBX: 00007ffe8bb25728 RCX: 00007fdd62b00840
> RDX: 00007fdd62aecea0 RSI: 0000000000000000 RDI: 00007ffe8bb26f1c
> RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000002 R11: 0000000000000246 R12: 000055f8a7dee8d0
> R13: 00007ffe8bb25720 R14: 0000000000000000 R15: 0000000000000000
>
> The buggy address belongs to the page:
> page:00000000b7dd9778 refcount:0 mapcount:-128 mapping:0000000000000000 index:0x0 pfn:0x228b8
> flags: 0xfff00000000000()
> raw: 00fff00000000000 ffffea0000580108 ffff88813fffb910 0000000000000000
> raw: 0000000000000000 0000000000000002 00000000ffffff7f 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>   ffff8880228b8780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>   ffff8880228b8800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>> ffff8880228b8880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>                                          ^
>   ffff8880228b8900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>   ffff8880228b8980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> ==================================================================
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> syzbot can test patches for this issue, for details see:
> https://goo.gl/tpsmEJ#testing-patches
>

Re: KASAN: use-after-free Read in v4l2_fh_open

[Hillf Danton]

On Mon, 15 Feb 2021 07:18:22 -0800
> syzbot found the following issue on:
> 
> HEAD commit:    291009f6 Merge tag 'pm-5.11-rc8' of git://git.kernel.org/p..
> git tree:       upstream
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17179dd4d00000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git  master

--- x/drivers/media/usb/em28xx/em28xx-video.c
+++ y/drivers/media/usb/em28xx/em28xx-video.c
@@ -2152,6 +2152,10 @@ static int em28xx_v4l2_open(struct file
 	if (mutex_lock_interruptible(&dev->lock))
 		return -ERESTARTSYS;
 
+	if (!dev->v4l2) {
+		mutex_unlock(&dev->lock);
+		return -ENODEV;
+	}
 	ret = v4l2_fh_open(filp);
 	if (ret) {
 		dev_err(&dev->intf->dev,
@@ -2161,6 +2165,7 @@ static int em28xx_v4l2_open(struct file
 		return ret;
 	}
 
+	v4l2 = dev->v4l2;
 	if (v4l2->users == 0) {
 		em28xx_set_mode(dev, EM28XX_ANALOG_MODE);
 
--

Re: [syzbot] [usb?] [media?] KASAN: use-after-free Read in v4l2_fh_open

[syzbot]

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+0x342/0x360 drivers/media/v4l2-core/v4l2-dev.c:432
Read of size 4 at addr ffff888024454800 by task v4l_id/5646

CPU: 1 PID: 5646 Comm: v4l_id Not tainted 6.8.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1b5/0x2a0 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0x163/0x510 mm/kasan/report.c:488
 kasan_report+0xcd/0x100 mm/kasan/report.c:601
 v4l2_open+0x342/0x360 drivers/media/v4l2-core/v4l2-dev.c:432
 chrdev_open+0x50f/0x5d0 fs/char_dev.c:414
 do_dentry_open+0x8fd/0x1590 fs/open.c:953
 path_openat+0x280d/0x31d0 fs/namei.c:3645
 do_filp_open+0x26d/0x500 fs/namei.c:3829
 do_sys_openat2+0x12f/0x1c0 fs/open.c:1404
 do_sys_open fs/open.c:1419 [inline]
 __do_sys_openat fs/open.c:1435 [inline]
 __se_sys_openat fs/open.c:1430 [inline]
 __x64_sys_openat+0x247/0x290 fs/open.c:1430
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x85/0x160 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7f3dabb169a4
Code: 24 20 48 8d 44 24 30 48 89 44 24 28 64 8b 04 25 18 00 00 00 85 c0 75 2c 44 89 e2 48 89 ee bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d 00 f0 ff ff 76 60 48 8b 15 55 a4 0d 00 f7 d8 64 89 02 48 83
RSP: 002b:00007ffc466ecd40 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007ffc466ecf58 RCX: 00007f3dabb169a4
RDX: 0000000000000000 RSI: 00007ffc466edf1e RDI: 00000000ffffff9c
RBP: 00007ffc466edf1e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffc466ecf70 R14: 0000555aa0ec0670 R15: 00007f3dac0aca80
 </TASK>

Allocated by task 8:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x30/0x60 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:370 [inline]
 __kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:387
 kasan_kmalloc include/linux/kasan.h:211 [inline]
 kmalloc_trace+0x1e6/0x400 mm/slub.c:4012
 kmalloc include/linux/slab.h:590 [inline]
 kzalloc include/linux/slab.h:711 [inline]
 em28xx_v4l2_init+0x107/0x2dc0 drivers/media/usb/em28xx/em28xx-video.c:2539
 em28xx_init_extension+0x11f/0x1c0 drivers/media/usb/em28xx/em28xx-core.c:1116
 process_scheduled_works+0x96f/0x1490 kernel/workqueue.c:2633
 worker_thread+0xa5f/0xff0 kernel/workqueue.c:2787
 kthread+0x2cd/0x360 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:243

Freed by task 8:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x30/0x60 mm/kasan/common.c:68
 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:589
 poison_slab_object+0xa6/0xe0 mm/kasan/common.c:240
 __kasan_slab_free+0x37/0x60 mm/kasan/common.c:256
 kasan_slab_free include/linux/kasan.h:184 [inline]
 slab_free_hook mm/slub.c:2121 [inline]
 slab_free mm/slub.c:4299 [inline]
 kfree+0x14a/0x370 mm/slub.c:4409
 em28xx_free_v4l2 drivers/media/usb/em28xx/em28xx-video.c:2120 [inline]
 kref_put include/linux/kref.h:65 [inline]
 em28xx_v4l2_init+0x1608/0x2dc0 drivers/media/usb/em28xx/em28xx-video.c:2908
 em28xx_init_extension+0x11f/0x1c0 drivers/media/usb/em28xx/em28xx-core.c:1116
 process_scheduled_works+0x96f/0x1490 kernel/workqueue.c:2633
 worker_thread+0xa5f/0xff0 kernel/workqueue.c:2787
 kthread+0x2cd/0x360 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:243

The buggy address belongs to the object at ffff888024454000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 2048 bytes inside of
 freed 8192-byte region [ffff888024454000, ffff888024456000)

The buggy address belongs to the physical page:
page:ffffea0000911400 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x24450
head:ffffea0000911400 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
anon flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888011442280 ffffea0001ede600 0000000000000005
raw: 0000000000000000 0000000080020002 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 4658, tgid 4658 (S41dhcpcd), ts 32416679882, free_ts 32403418572
 prep_new_page mm/page_alloc.c:1540 [inline]
 get_page_from_freelist+0x3355/0x34e0 mm/page_alloc.c:3311
 __alloc_pages+0x255/0x670 mm/page_alloc.c:4567
 alloc_slab_page+0x5f/0x150 include/linux/gfp.h:238
 new_slab+0x84/0x2f0 mm/slub.c:2354
 ___slab_alloc+0xc77/0x1310 mm/slub.c:3540
 kmalloc_trace+0x276/0x400 mm/slub.c:3625
 kmalloc include/linux/slab.h:590 [inline]
 kzalloc include/linux/slab.h:711 [inline]
 tomoyo_print_bprm security/tomoyo/audit.c:26 [inline]
 tomoyo_init_log+0x1228/0x2130 security/tomoyo/audit.c:264
 tomoyo_supervisor+0x37a/0x1370 security/tomoyo/common.c:2089
 tomoyo_audit_env_log security/tomoyo/environ.c:36 [inline]
 tomoyo_env_perm+0x157/0x1f0 security/tomoyo/environ.c:63
 tomoyo_find_next_domain+0x139a/0x1d40 security/tomoyo/domain.c:672
 tomoyo_bprm_check_security+0x114/0x170 security/tomoyo/tomoyo.c:102
 security_bprm_check+0x63/0xa0 security/security.c:1188
 bprm_execve+0xa45/0x1840 fs/exec.c:1771
 do_execveat_common+0x552/0x6f0 fs/exec.c:1984
 do_execve fs/exec.c:2058 [inline]
 __do_sys_execve fs/exec.c:2134 [inline]
 __se_sys_execve fs/exec.c:2129 [inline]
 __x64_sys_execve+0x92/0xa0 fs/exec.c:2129
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x85/0x160 arch/x86/entry/common.c:83
page last free pid 4657 tgid 4657 stack trace:
 free_unref_page_prepare+0x94d/0xa60 include/linux/page_owner.h:24
 free_unref_page+0x37/0x3f0 mm/page_alloc.c:2486
 __put_partials+0xeb/0x130 mm/slub.c:2453
 put_cpu_partial+0x169/0x240 mm/slub.c:2997
 __slab_free+0x2c3/0x400 mm/slub.c:4166
 qlist_free_all+0x5e/0xc0 mm/kasan/quarantine.c:163
 kasan_quarantine_reduce+0x14b/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x23/0x70 mm/kasan/common.c:322
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook mm/slub.c:3813 [inline]
 slab_alloc_node mm/slub.c:3860 [inline]
 __do_kmalloc_node mm/slub.c:3980 [inline]
 __kmalloc+0x1dd/0x540 mm/slub.c:3994
 kmalloc include/linux/slab.h:594 [inline]
 tomoyo_realpath_from_path+0xcf/0x5e0 security/tomoyo/realpath.c:251
 tomoyo_path_perm+0x24d/0x5b0 security/tomoyo/file.c:151
 security_inode_getattr+0xd3/0x120 security/security.c:2238
 vfs_fstatat+0xca/0x1b0 fs/stat.c:173
 __se_sys_newfstatat fs/stat.c:468 [inline]
 __x64_sys_newfstatat+0xff/0x170 fs/stat.c:462
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x85/0x160 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

Memory state around the buggy address:
 ffff888024454700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888024454780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888024454800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff888024454880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888024454900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


Tested on:

commit:         5ad3cb0e Merge tag 'for-v6.8-rc2' of git://git.kernel...
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=163afbac180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fa01a41dc74de670
dashboard link: https://syzkaller.appspot.com/bug?extid=b2391895514ed9ef4a8e
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=15d84096180000

Re: KASAN: use-after-free Read in v4l2_fh_open

[Hillf Danton]

On Mon, 15 Feb 2021 07:18:22 -0800
> syzbot found the following issue on:
> 
> HEAD commit:    291009f6 Merge tag 'pm-5.11-rc8' of git://git.kernel.org/p..
> git tree:       upstream
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17179dd4d00000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git  master

--- x/drivers/media/usb/em28xx/em28xx-video.c
+++ y/drivers/media/usb/em28xx/em28xx-video.c
@@ -2152,6 +2152,10 @@ static int em28xx_v4l2_open(struct file
 	if (mutex_lock_interruptible(&dev->lock))
 		return -ERESTARTSYS;
 
+	if (!dev->v4l2) {
+		mutex_unlock(&dev->lock);
+		return -ENODEV;
+	}
 	ret = v4l2_fh_open(filp);
 	if (ret) {
 		dev_err(&dev->intf->dev,
@@ -2161,6 +2165,7 @@ static int em28xx_v4l2_open(struct file
 		return ret;
 	}
 
+	v4l2 = dev->v4l2;
 	if (v4l2->users == 0) {
 		em28xx_set_mode(dev, EM28XX_ANALOG_MODE);
 
@@ -2899,6 +2904,7 @@ unregister_dev:
 	v4l2_ctrl_handler_free(&v4l2->ctrl_handler);
 	v4l2_device_unregister(&v4l2->v4l2_dev);
 err:
+	video_unregister_device(&v4l2->vdev);
 	dev->v4l2 = NULL;
 	kref_put(&v4l2->ref, em28xx_free_v4l2);
 	mutex_unlock(&dev->lock);
--

Re: [syzbot] [usb?] [media?] KASAN: use-after-free Read in v4l2_fh_open

[syzbot]

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+0x342/0x360 drivers/media/v4l2-core/v4l2-dev.c:432
Read of size 4 at addr ffff8880257b8800 by task v4l_id/5638

CPU: 1 PID: 5638 Comm: v4l_id Not tainted 6.8.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1b5/0x2a0 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0x163/0x510 mm/kasan/report.c:488
 kasan_report+0xcd/0x100 mm/kasan/report.c:601
 v4l2_open+0x342/0x360 drivers/media/v4l2-core/v4l2-dev.c:432
 chrdev_open+0x50f/0x5d0 fs/char_dev.c:414
 do_dentry_open+0x8fd/0x1590 fs/open.c:953
 path_openat+0x280d/0x31d0 fs/namei.c:3645
 do_filp_open+0x26d/0x500 fs/namei.c:3829
 do_sys_openat2+0x12f/0x1c0 fs/open.c:1404
 do_sys_open fs/open.c:1419 [inline]
 __do_sys_openat fs/open.c:1435 [inline]
 __se_sys_openat fs/open.c:1430 [inline]
 __x64_sys_openat+0x247/0x290 fs/open.c:1430
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x85/0x160 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7fd0c998f9a4
Code: 24 20 48 8d 44 24 30 48 89 44 24 28 64 8b 04 25 18 00 00 00 85 c0 75 2c 44 89 e2 48 89 ee bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d 00 f0 ff ff 76 60 48 8b 15 55 a4 0d 00 f7 d8 64 89 02 48 83
RSP: 002b:00007ffe99c37580 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007ffe99c37798 RCX: 00007fd0c998f9a4
RDX: 0000000000000000 RSI: 00007ffe99c38f1e RDI: 00000000ffffff9c
RBP: 00007ffe99c38f1e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffe99c377b0 R14: 000056109fa30670 R15: 00007fd0c9b4aa80
 </TASK>

Allocated by task 5003:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x30/0x60 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:370 [inline]
 __kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:387
 kasan_kmalloc include/linux/kasan.h:211 [inline]
 kmalloc_trace+0x1e6/0x400 mm/slub.c:4012
 kmalloc include/linux/slab.h:590 [inline]
 kzalloc include/linux/slab.h:711 [inline]
 em28xx_v4l2_init+0x107/0x2dd0 drivers/media/usb/em28xx/em28xx-video.c:2539
 em28xx_init_extension+0x11f/0x1c0 drivers/media/usb/em28xx/em28xx-core.c:1116
 process_scheduled_works+0x96f/0x1490 kernel/workqueue.c:2633
 worker_thread+0xa5f/0xff0 kernel/workqueue.c:2787
 kthread+0x2cd/0x360 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:243

Freed by task 5003:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x30/0x60 mm/kasan/common.c:68
 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:589
 poison_slab_object+0xa6/0xe0 mm/kasan/common.c:240
 __kasan_slab_free+0x37/0x60 mm/kasan/common.c:256
 kasan_slab_free include/linux/kasan.h:184 [inline]
 slab_free_hook mm/slub.c:2121 [inline]
 slab_free mm/slub.c:4299 [inline]
 kfree+0x14a/0x370 mm/slub.c:4409
 em28xx_free_v4l2 drivers/media/usb/em28xx/em28xx-video.c:2120 [inline]
 kref_put include/linux/kref.h:65 [inline]
 em28xx_v4l2_init+0x1618/0x2dd0 drivers/media/usb/em28xx/em28xx-video.c:2909
 em28xx_init_extension+0x11f/0x1c0 drivers/media/usb/em28xx/em28xx-core.c:1116
 process_scheduled_works+0x96f/0x1490 kernel/workqueue.c:2633
 worker_thread+0xa5f/0xff0 kernel/workqueue.c:2787
 kthread+0x2cd/0x360 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:243

The buggy address belongs to the object at ffff8880257b8000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 2048 bytes inside of
 freed 8192-byte region [ffff8880257b8000, ffff8880257ba000)

The buggy address belongs to the physical page:
page:ffffea000095ee00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x257b8
head:ffffea000095ee00 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888011442280 ffffea00007c9c00 0000000000000006
raw: 0000000000000000 0000000080020002 00000001ffffffff 0000000000000000
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 4662, tgid 4662 (dhcpcd), ts 31219348806, free_ts 31206911230
 prep_new_page mm/page_alloc.c:1540 [inline]
 get_page_from_freelist+0x3355/0x34e0 mm/page_alloc.c:3311
 __alloc_pages+0x255/0x670 mm/page_alloc.c:4567
 alloc_slab_page+0x5f/0x150 include/linux/gfp.h:238
 new_slab+0x84/0x2f0 mm/slub.c:2354
 ___slab_alloc+0xc77/0x1310 mm/slub.c:3540
 __kmalloc_node_track_caller+0x2e9/0x570 mm/slub.c:3625
 kmalloc_reserve+0xf3/0x260 net/core/skbuff.c:582
 __alloc_skb+0x19f/0x3d0 net/core/skbuff.c:651
 alloc_skb include/linux/skbuff.h:1296 [inline]
 netlink_dump+0x204/0xc70 net/netlink/af_netlink.c:2231
 netlink_recvmsg+0x671/0x10f0 net/netlink/af_netlink.c:1990
 ____sys_recvmsg+0x28b/0x570 net/socket.c:1046
 __sys_recvmsg+0x280/0x360 net/socket.c:2845
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x85/0x160 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
page last free pid 4662 tgid 4662 stack trace:
 free_unref_page_prepare+0x94d/0xa60 include/linux/page_owner.h:24
 free_unref_page+0x37/0x3f0 mm/page_alloc.c:2486
 __put_partials+0xeb/0x130 mm/slub.c:2453
 put_cpu_partial+0x169/0x240 mm/slub.c:2997
 __slab_free+0x2c3/0x400 mm/slub.c:4166
 qlist_free_all+0x5e/0xc0 mm/kasan/quarantine.c:163
 kasan_quarantine_reduce+0x14b/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x23/0x70 mm/kasan/common.c:322
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook mm/slub.c:3813 [inline]
 slab_alloc_node mm/slub.c:3860 [inline]
 __do_kmalloc_node mm/slub.c:3980 [inline]
 __kmalloc+0x1dd/0x540 mm/slub.c:3994
 kmalloc include/linux/slab.h:594 [inline]
 tomoyo_add_entry security/tomoyo/common.c:2023 [inline]
 tomoyo_supervisor+0xdf1/0x1370 security/tomoyo/common.c:2095
 tomoyo_path_permission+0x243/0x360 security/tomoyo/file.c:168
 tomoyo_path_perm+0x442/0x5b0 security/tomoyo/file.c:838
 security_inode_getattr+0xd3/0x120 security/security.c:2238
 vfs_fstatat+0xca/0x1b0 fs/stat.c:173
 __se_sys_newfstatat fs/stat.c:468 [inline]
 __x64_sys_newfstatat+0xff/0x170 fs/stat.c:462
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x85/0x160 arch/x86/entry/common.c:83

Memory state around the buggy address:
 ffff8880257b8700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880257b8780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880257b8800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff8880257b8880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880257b8900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


Tested on:

commit:         04b8076d Merge tag 'firewire-fixes-6.8-rc7' of git://g..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=10309dca180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fa01a41dc74de670
dashboard link: https://syzkaller.appspot.com/bug?extid=b2391895514ed9ef4a8e
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=112b2732180000

Re: KASAN: use-after-free Read in v4l2_fh_open

[Hillf Danton]

On Mon, 15 Feb 2021 07:18:22 -0800
> syzbot found the following issue on:
> 
> HEAD commit:    291009f6 Merge tag 'pm-5.11-rc8' of git://git.kernel.org/p..
> git tree:       upstream
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17179dd4d00000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git  master

--- x/drivers/media/usb/em28xx/em28xx-video.c
+++ y/drivers/media/usb/em28xx/em28xx-video.c
@@ -2152,6 +2152,10 @@ static int em28xx_v4l2_open(struct file
 	if (mutex_lock_interruptible(&dev->lock))
 		return -ERESTARTSYS;
 
+	if (!dev->v4l2) {
+		mutex_unlock(&dev->lock);
+		return -ENODEV;
+	}
 	ret = v4l2_fh_open(filp);
 	if (ret) {
 		dev_err(&dev->intf->dev,
@@ -2161,6 +2165,7 @@ static int em28xx_v4l2_open(struct file
 		return ret;
 	}
 
+	v4l2 = dev->v4l2;
 	if (v4l2->users == 0) {
 		em28xx_set_mode(dev, EM28XX_ANALOG_MODE);
 
@@ -2376,10 +2381,17 @@ static const struct v4l2_ioctl_ops video
 #endif
 };
 
+static void em28xx_video_device_release(struct video_device *vd)
+{
+	struct em28xx_v4l2 *v4l2 = container_of(vd, struct em28xx_v4l2, vdev);
+
+	kref_put(&v4l2->ref, em28xx_free_v4l2);
+}
+
 static const struct video_device em28xx_video_template = {
 	.fops		= &em28xx_v4l_fops,
 	.ioctl_ops	= &video_ioctl_ops,
-	.release	= video_device_release_empty,
+	.release	= em28xx_video_device_release,
 	.tvnorms	= V4L2_STD_ALL,
 };
 
@@ -2788,6 +2800,7 @@ static int em28xx_v4l2_init(struct em28x
 			"unable to register video device (error=%i).\n", ret);
 		goto unregister_dev;
 	}
+	kref_get(&v4l2->ref); /* put by video_unregister_device() */
 
 	/* Allocate and fill vbi video_device struct */
 	if (em28xx_vbi_supported(dev) == 1) {
--

Re: [syzbot] [usb?] [media?] KASAN: use-after-free Read in v4l2_fh_open

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+b2391895514ed9ef4a8e@syzkaller.appspotmail.com

Tested on:

commit:         04b8076d Merge tag 'firewire-fixes-6.8-rc7' of git://g..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=12012abc180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fa01a41dc74de670
dashboard link: https://syzkaller.appspot.com/bug?extid=b2391895514ed9ef4a8e
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1709bcf2180000

Note: testing is done by a robot and is best-effort only.