[btrfs?] KASAN: use-after-free Read in caching_kthread

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syzbot

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Dec 18, 2022, 6:20:52 AM12/18/22

to syzkaller...@googlegroups.com

Hello,

syzbot found the following issue on:

HEAD commit: 3f8a27f9e27b Linux 4.19.211
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1067f01b880000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b9277b418617afe
dashboard link: https://syzkaller.appspot.com/bug?extid=8735475417a0d7d4f0db
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/98c0bdb4abb3/disk-3f8a27f9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ea228ff02669/vmlinux-3f8a27f9.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+873547...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in caching_kthread+0x871/0x970 fs/btrfs/inode-map.c:31
Read of size 8 at addr ffff888096b70d70 by task btrfs-ino-cache/29855

CPU: 0 PID: 29855 Comm: btrfs-ino-cache Not tainted 4.19.211-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
print_address_description.cold+0x54/0x219 mm/kasan/report.c:256
kasan_report_error.cold+0x8a/0x1b9 mm/kasan/report.c:354
kasan_report mm/kasan/report.c:412 [inline]
__asan_report_load8_noabort+0x88/0x90 mm/kasan/report.c:433
caching_kthread+0x871/0x970 fs/btrfs/inode-map.c:31
kthread+0x33f/0x460 kernel/kthread.c:259
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

Allocated by task 29786:
kmem_cache_alloc_trace+0x12f/0x380 mm/slab.c:3625
kmalloc include/linux/slab.h:515 [inline]
kzalloc include/linux/slab.h:709 [inline]
btrfs_alloc_root fs/btrfs/disk-io.c:1220 [inline]
btrfs_read_tree_root+0x94/0x560 fs/btrfs/disk-io.c:1421
btrfs_read_fs_root fs/btrfs/disk-io.c:1467 [inline]
btrfs_get_fs_root+0x239/0x890 fs/btrfs/disk-io.c:1601
btrfs_read_fs_root_no_name fs/btrfs/disk-io.h:80 [inline]
open_ctree+0x469c/0x61e0 fs/btrfs/disk-io.c:3181
btrfs_fill_super fs/btrfs/super.c:1209 [inline]
btrfs_mount_root+0x12e5/0x1830 fs/btrfs/super.c:1613
mount_fs+0xa3/0x310 fs/super.c:1261
vfs_kern_mount.part.0+0x68/0x470 fs/namespace.c:961
vfs_kern_mount+0x3c/0x60 fs/namespace.c:951
btrfs_mount+0x23a/0xaa0 fs/btrfs/super.c:1681
mount_fs+0xa3/0x310 fs/super.c:1261
vfs_kern_mount.part.0+0x68/0x470 fs/namespace.c:961
vfs_kern_mount fs/namespace.c:951 [inline]
do_new_mount fs/namespace.c:2492 [inline]
do_mount+0x115c/0x2f50 fs/namespace.c:2822
ksys_mount+0xcf/0x130 fs/namespace.c:3038
__do_sys_mount fs/namespace.c:3052 [inline]
__se_sys_mount fs/namespace.c:3049 [inline]
__x64_sys_mount+0xba/0x150 fs/namespace.c:3049
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 8143:
__cache_free mm/slab.c:3503 [inline]
kfree+0xcc/0x210 mm/slab.c:3822
btrfs_put_fs_root fs/btrfs/disk-io.h:111 [inline]
btrfs_free_fs_root+0x1e6/0x260 fs/btrfs/disk-io.c:3861
btrfs_free_fs_roots+0x2ef/0x4d0 fs/btrfs/disk-io.c:2092
close_ctree+0x306/0x850 fs/btrfs/disk-io.c:4017
generic_shutdown_super+0x144/0x370 fs/super.c:456
kill_anon_super+0x36/0x60 fs/super.c:1032
btrfs_kill_super+0x49/0x550 fs/btrfs/super.c:2221
deactivate_locked_super+0x94/0x160 fs/super.c:329
deactivate_super+0x174/0x1a0 fs/super.c:360
cleanup_mnt+0x1a8/0x290 fs/namespace.c:1098
task_work_run+0x148/0x1c0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:193 [inline]
exit_to_usermode_loop+0x251/0x2a0 arch/x86/entry/common.c:167
prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath arch/x86/entry/common.c:271 [inline]
do_syscall_64+0x538/0x620 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff888096b70b80
which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 496 bytes inside of
4096-byte region [ffff888096b70b80, ffff888096b71b80)
The buggy address belongs to the page:
page:ffffea00025adc00 count:1 mapcount:0 mapping:ffff88813bff0dc0 index:0x0 compound_mapcount: 0
flags: 0xfff00000008100(slab|head)
raw: 00fff00000008100 ffffea0000daa508 ffffea0000e13708 ffff88813bff0dc0
raw: 0000000000000000 ffff888096b70b80 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888096b70c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888096b70c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888096b70d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888096b70d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888096b70e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
BTRFS warning (device <unknown>): duplicate device /dev/loop4 devid 1 generation 8 scanned by syz-executor.4 (29767)

---
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 syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

syzbot

unread,

Dec 31, 2022, 9:19:35 AM12/31/22

to syzkaller...@googlegroups.com

syzbot has found a reproducer for the following issue on:

HEAD commit: 3f8a27f9e27b Linux 4.19.211
git tree: linux-4.19.y

console output: https://syzkaller.appspot.com/x/log.txt?x=11dc2632480000

kernel config: https://syzkaller.appspot.com/x/.config?x=9b9277b418617afe
dashboard link: https://syzkaller.appspot.com/bug?extid=8735475417a0d7d4f0db
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14b84ac0480000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/98c0bdb4abb3/disk-3f8a27f9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ea228ff02669/vmlinux-3f8a27f9.xz

mounted in repro: https://storage.googleapis.com/syzbot-assets/9ffe0c225b1f/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+873547...@syzkaller.appspotmail.com

BTRFS warning (device <unknown>): duplicate device /dev/loop5 devid 1 generation 8 scanned by systemd-udevd (16130)
BTRFS warning (device <unknown>): duplicate device /dev/loop4 devid 1 generation 8 scanned by systemd-udevd (16141)
BTRFS warning (device <unknown>): duplicate device /dev/loop3 devid 1 generation 8 scanned by syz-executor.3 (16114)

==================================================================
BUG: KASAN: use-after-free in caching_kthread+0x871/0x970 fs/btrfs/inode-map.c:31

Read of size 8 at addr ffff8880986def70 by task btrfs-ino-cache/16164

CPU: 0 PID: 16164 Comm: btrfs-ino-cache Not tainted 4.19.211-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
print_address_description.cold+0x54/0x219 mm/kasan/report.c:256
kasan_report_error.cold+0x8a/0x1b9 mm/kasan/report.c:354
kasan_report mm/kasan/report.c:412 [inline]
__asan_report_load8_noabort+0x88/0x90 mm/kasan/report.c:433
caching_kthread+0x871/0x970 fs/btrfs/inode-map.c:31
kthread+0x33f/0x460 kernel/kthread.c:259
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

Allocated by task 16073:

Freed by task 8168:

__cache_free mm/slab.c:3503 [inline]
kfree+0xcc/0x210 mm/slab.c:3822
btrfs_put_fs_root fs/btrfs/disk-io.h:111 [inline]
btrfs_free_fs_root+0x1e6/0x260 fs/btrfs/disk-io.c:3861
btrfs_free_fs_roots+0x2ef/0x4d0 fs/btrfs/disk-io.c:2092
close_ctree+0x306/0x850 fs/btrfs/disk-io.c:4017
generic_shutdown_super+0x144/0x370 fs/super.c:456
kill_anon_super+0x36/0x60 fs/super.c:1032
btrfs_kill_super+0x49/0x550 fs/btrfs/super.c:2221
deactivate_locked_super+0x94/0x160 fs/super.c:329
deactivate_super+0x174/0x1a0 fs/super.c:360
cleanup_mnt+0x1a8/0x290 fs/namespace.c:1098
task_work_run+0x148/0x1c0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:193 [inline]
exit_to_usermode_loop+0x251/0x2a0 arch/x86/entry/common.c:167
prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath arch/x86/entry/common.c:271 [inline]
do_syscall_64+0x538/0x620 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880986ded80

which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 496 bytes inside of

4096-byte region [ffff8880986ded80, ffff8880986dfd80)

The buggy address belongs to the page:

page:ffffea000261b780 count:1 mapcount:0 mapping:ffff88813bff0dc0 index:0x0 compound_mapcount: 0
flags: 0xfff00000008100(slab|head)
raw: 00fff00000008100 ffffea0001f8fa08 ffffea0002680f88 ffff88813bff0dc0
raw: 0000000000000000 ffff8880986ded80 0000000100000001 0000000000000000

page dumped because: kasan: bad access detected

Memory state around the buggy address:

ffff8880986dee00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880986dee80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880986def00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880986def80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880986df000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

syzbot

unread,

Jan 12, 2023, 4:42:41 AM1/12/23

to syzkaller...@googlegroups.com

syzbot has found a reproducer for the following issue on:

HEAD commit: 3f8a27f9e27b Linux 4.19.211
git tree: linux-4.19.y

console output: https://syzkaller.appspot.com/x/log.txt?x=10031491480000

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=144feba4480000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11085fba480000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/98c0bdb4abb3/disk-3f8a27f9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ea228ff02669/vmlinux-3f8a27f9.xz

mounted in repro: https://storage.googleapis.com/syzbot-assets/50b7bdec324e/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+873547...@syzkaller.appspotmail.com

BTRFS info (device loop0): has skinny extents
BTRFS info (device loop0): clearing free space tree
BTRFS info (device loop0): clearing 1 ro feature flag
BTRFS info (device loop0): clearing 2 ro feature flag

==================================================================
BUG: KASAN: use-after-free in caching_kthread+0x871/0x970 fs/btrfs/inode-map.c:31

Read of size 8 at addr ffff88809147a7f0 by task btrfs-ino-cache/11097

CPU: 1 PID: 11097 Comm: btrfs-ino-cache Not tainted 4.19.211-syzkaller #0

Allocated by task 11070:

Freed by task 8127:

The buggy address belongs to the object at ffff88809147a600

which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 496 bytes inside of

4096-byte region [ffff88809147a600, ffff88809147b600)

The buggy address belongs to the page:

page:ffffea0002451e80 count:1 mapcount:0 mapping:ffff88813bff0dc0 index:0x0 compound_mapcount: 0
flags: 0xfff00000008100(slab|head)
raw: 00fff00000008100 ffffea0002452088 ffffea00023f5c88 ffff88813bff0dc0
raw: 0000000000000000 ffff88809147a600 0000000100000001 0000000000000000

page dumped because: kasan: bad access detected

Memory state around the buggy address:

ffff88809147a680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88809147a700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88809147a780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88809147a800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88809147a880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

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