[v5.15] KASAN: use-after-free Read in hpfs_get_ea

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c79648372d02 Linux 5.15.189
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1243c8a2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=9e47345638b85bd0
dashboard link: https://syzkaller.appspot.com/bug?extid=1ded3afdecabdd33273d
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
userspace arch: arm64

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7ab49562317a/disk-c7964837.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e847ec1e38d3/vmlinux-c7964837.xz
kernel image: https://storage.googleapis.com/syzbot-assets/263158c6371c/Image-c7964837.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1ded3a...@syzkaller.appspotmail.com

hpfs: You really don't want any checks? You are crazy...
hpfs: hpfs_map_sector(): read error
hpfs: code page support is disabled
==================================================================
BUG: KASAN: use-after-free in strcmp+0xc0/0xf4 lib/string.c:400
Read of size 1 at addr ffff0000ec0d38a6 by task syz.1.15/4202

CPU: 1 PID: 4202 Comm: syz.1.15 Not tainted 5.15.189-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call trace:
dump_backtrace+0x0/0x43c arch/arm64/kernel/stacktrace.c:152
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
__dump_stack+0x30/0x40 lib/dump_stack.c:88
dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106
print_address_description+0x78/0x30c mm/kasan/report.c:248
__kasan_report mm/kasan/report.c:434 [inline]
kasan_report+0xec/0x15c mm/kasan/report.c:451
__asan_report_load1_noabort+0x44/0x50 mm/kasan/report_generic.c:306
strcmp+0xc0/0xf4 lib/string.c:400
hpfs_get_ea+0xfc/0x958 fs/hpfs/ea.c:139
hpfs_read_inode+0x15c/0xcac fs/hpfs/inode.c:63
hpfs_fill_super+0xe64/0x1800 fs/hpfs/super.c:712
mount_bdev+0x264/0x358 fs/super.c:1400
hpfs_mount+0x44/0x58 fs/hpfs/super.c:758
legacy_get_tree+0xd4/0x16c fs/fs_context.c:611
vfs_get_tree+0x90/0x274 fs/super.c:1530
do_new_mount+0x228/0x810 fs/namespace.c:3014
path_mount+0x5b4/0x1000 fs/namespace.c:3344
do_mount fs/namespace.c:3357 [inline]
__do_sys_mount fs/namespace.c:3565 [inline]
__se_sys_mount fs/namespace.c:3542 [inline]
__arm64_sys_mount+0x514/0x5e4 fs/namespace.c:3542
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

The buggy address belongs to the page:
page:00000000f07c9f41 refcount:0 mapcount:0 mapping:0000000000000000 index:0x100 pfn:0x12c0d3
flags: 0x5ffc00000000000(node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000100 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff0000ec0d3780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff0000ec0d3800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff0000ec0d3880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff0000ec0d3900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff0000ec0d3980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
hpfs: hpfs_map_sector(): read error
hpfs: hpfs_map_sector(): read error
hpfs: hpfs_map_sector(): read error
hpfs: hpfs_map_sector(): read error
hpfs: hpfs_map_4sectors(): unaligned read
hpfs: hpfs_map_4sectors(): unaligned read
hpfs: filesystem error: unable to find root dir


---
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.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: c79648372d02 Linux 5.15.189
git tree: linux-5.15.y

console output: https://syzkaller.appspot.com/x/log.txt?x=116b4034580000

kernel config: https://syzkaller.appspot.com/x/.config?x=9e47345638b85bd0
dashboard link: https://syzkaller.appspot.com/bug?extid=1ded3afdecabdd33273d
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
userspace arch: arm64

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=140534f0580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15d368a2580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7ab49562317a/disk-c7964837.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e847ec1e38d3/vmlinux-c7964837.xz
kernel image: https://storage.googleapis.com/syzbot-assets/263158c6371c/Image-c7964837.gz.xz

mounted in repro: https://storage.googleapis.com/syzbot-assets/797653cbca3b/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1ded3a...@syzkaller.appspotmail.com

hpfs: You really don't want any checks? You are crazy...
hpfs: hpfs_map_sector(): read error
hpfs: code page support is disabled
==================================================================
BUG: KASAN: use-after-free in strcmp+0xc0/0xf4 lib/string.c:400

Read of size 1 at addr ffff0000eb4288a6 by task syz.0.16/4313

CPU: 0 PID: 4313 Comm: syz.0.16 Not tainted 5.15.189-syzkaller #0

page:0000000045d11a1c refcount:0 mapcount:0 mapping:0000000000000000 index:0x100 pfn:0x12b428

flags: 0x5ffc00000000000(node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000100 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:

ffff0000eb428780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff0000eb428800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff0000eb428880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff0000eb428900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff0000eb428980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff

==================================================================
hpfs: hpfs_map_sector(): read error
hpfs: hpfs_map_sector(): read error
hpfs: hpfs_map_sector(): read error
hpfs: hpfs_map_sector(): read error
hpfs: hpfs_map_4sectors(): unaligned read
hpfs: hpfs_map_4sectors(): unaligned read
hpfs: filesystem error: unable to find root dir


---

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.

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3594f306da12 Linux 6.1.147
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13852782580000
kernel config: https://syzkaller.appspot.com/x/.config?x=2be97b627a5d7554
dashboard link: https://syzkaller.appspot.com/bug?extid=98d90f982e59bdb12f21

compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
userspace arch: arm64

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0d2a884e198e/disk-3594f306.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/23d3643328c7/vmlinux-3594f306.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ef83d78711e3/Image-3594f306.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by: syzbot+98d90f...@syzkaller.appspotmail.com

hpfs: hpfs_map_sector(): read error
hpfs: code page support is disabled
==================================================================

BUG: KASAN: use-after-free in strcmp+0xc0/0xf4 lib/string.c:361
Read of size 1 at addr ffff0000fd7588a6 by task syz.4.92/4927

CPU: 1 PID: 4927 Comm: syz.4.92 Not tainted 6.1.147-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call trace:

dump_backtrace+0x1c8/0x1f4 arch/arm64/kernel/stacktrace.c:158
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165

__dump_stack+0x30/0x40 lib/dump_stack.c:88
dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106

print_address_description+0x88/0x200 mm/kasan/report.c:316
print_report+0x50/0x68 mm/kasan/report.c:418
kasan_report+0xa8/0x100 mm/kasan/report.c:522
__asan_report_load1_noabort+0x2c/0x38 mm/kasan/report_generic.c:348
strcmp+0xc0/0xf4 lib/string.c:361
hpfs_get_ea+0xfc/0x968 fs/hpfs/ea.c:139

hpfs_read_inode+0x15c/0xcac fs/hpfs/inode.c:63
hpfs_fill_super+0xe64/0x1800 fs/hpfs/super.c:712

mount_bdev+0x264/0x358 fs/super.c:1443
hpfs_mount+0x44/0x58 fs/hpfs/super.c:758
legacy_get_tree+0xd4/0x16c fs/fs_context.c:632
vfs_get_tree+0x90/0x274 fs/super.c:1573
do_new_mount+0x228/0x810 fs/namespace.c:3063
path_mount+0x5b4/0xe78 fs/namespace.c:3393
do_mount fs/namespace.c:3406 [inline]
__do_sys_mount fs/namespace.c:3614 [inline]
__se_sys_mount fs/namespace.c:3591 [inline]
__arm64_sys_mount+0x49c/0x584 fs/namespace.c:3591
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

The buggy address belongs to the physical page:
page:000000003de3ad37 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x13d758

flags: 0x5ffc00000000000(node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000000000 dead000000000100 dead000000000122 0000000000000000

raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000

page dumped because: kasan: bad access detected

Memory state around the buggy address:

ffff0000fd758780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff0000fd758800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff0000fd758880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff0000fd758900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff0000fd758980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff

==================================================================
hpfs: hpfs_map_sector(): read error
hpfs: hpfs_map_sector(): read error
hpfs: hpfs_map_sector(): read error
hpfs: hpfs_map_sector(): read error
hpfs: hpfs_map_4sectors(): unaligned read
hpfs: hpfs_map_4sectors(): unaligned read
hpfs: filesystem error: unable to find root dir


---

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dbcb8d8e4163 Linux 6.6.100
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=148674f0580000
kernel config: https://syzkaller.appspot.com/x/.config?x=293251cfa8d8100
dashboard link: https://syzkaller.appspot.com/bug?extid=91209a63bd6e8b2608e4

compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

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

Downloadable assets:

disk image: https://storage.googleapis.com/syzbot-assets/d0b56817a2c3/disk-dbcb8d8e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f0d646b2f7fa/vmlinux-dbcb8d8e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1e0b752a5011/bzImage-dbcb8d8e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by: syzbot+91209a...@syzkaller.appspotmail.com

hpfs: filesystem error: improperly stopped

hpfs: You really don't want any checks? You are crazy...

hpfs: hpfs_map_sector(): read error
hpfs: code page support is disabled
==================================================================

BUG: KASAN: use-after-free in strcmp+0x6f/0xb0 lib/string.c:288
Read of size 1 at addr ffff88805b983003 by task syz.0.101/6234

CPU: 1 PID: 6234 Comm: syz.0.101 Not tainted 6.6.100-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025

Call Trace:
<TASK>
dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:364 [inline]
print_report+0xac/0x200 mm/kasan/report.c:466
kasan_report+0x117/0x150 mm/kasan/report.c:579
strcmp+0x6f/0xb0 lib/string.c:288
hpfs_get_ea+0x115/0xda0 fs/hpfs/ea.c:139
hpfs_read_inode+0x19e/0x1010 fs/hpfs/inode.c:63
hpfs_fill_super+0x12d5/0x1ec0 fs/hpfs/super.c:712
mount_bdev+0x22b/0x2d0 fs/super.c:1643
legacy_get_tree+0xea/0x180 fs/fs_context.c:662
vfs_get_tree+0x8c/0x280 fs/super.c:1764
do_new_mount+0x24b/0xa40 fs/namespace.c:3371
do_mount fs/namespace.c:3711 [inline]
__do_sys_mount fs/namespace.c:3920 [inline]
__se_sys_mount+0x2da/0x3c0 fs/namespace.c:3897
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f26f159014a
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 1a 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 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:00007f26f23dfe68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f26f23dfef0 RCX: 00007f26f159014a
RDX: 0000200000009e80 RSI: 0000200000009ec0 RDI: 00007f26f23dfeb0
RBP: 0000200000009e80 R08: 00007f26f23dfef0 R09: 0000000000000041
R10: 0000000000000041 R11: 0000000000000246 R12: 0000200000009ec0
R13: 00007f26f23dfeb0 R14: 0000000000009e05 R15: 0000200000009f00
</TASK>

The buggy address belongs to the physical page:

page:ffffea00016e60c0 refcount:1 mapcount:0 mapping:ffff8880183a7cc0 index:0xd0d pfn:0x5b983
memcg:ffff888024650000
aops:shmem_aops ino:21 dentry name(?):"memfd:syzkaller"
flags: 0xfff6000008003c(referenced|uptodate|dirty|lru|swapbacked|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff6000008003c ffffea0001b62488 ffffea00016e2008 ffff8880183a7cc0
raw: 0000000000000d0d 0000000000000000 00000001ffffffff ffff888024650000

page dumped because: kasan: bad access detected

page_owner tracks the page as allocated
page last allocated via order 0, migratetype Movable, gfp_mask 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 6225, tgid 6224 (syz.2.98), ts 113677551023, free_ts 111267244794
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
prep_new_page mm/page_alloc.c:1561 [inline]
get_page_from_freelist+0x195c/0x19f0 mm/page_alloc.c:3191
__alloc_pages+0x1e3/0x460 mm/page_alloc.c:4457
__folio_alloc+0x10/0x20 mm/page_alloc.c:4489
vma_alloc_folio+0x47a/0x8f0 mm/mempolicy.c:2242
shmem_alloc_folio+0x179/0x230 mm/shmem.c:1680
shmem_alloc_and_acct_folio+0x189/0x630 mm/shmem.c:1705
shmem_get_folio_gfp+0xcde/0x2ac0 mm/shmem.c:2042
shmem_get_folio mm/shmem.c:2165 [inline]
shmem_write_begin+0xf2/0x420 mm/shmem.c:2707
generic_perform_write+0x2fb/0x5b0 mm/filemap.c:4016
shmem_file_write_iter+0xfb/0x120 mm/shmem.c:2884
call_write_iter include/linux/fs.h:2018 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x43b/0x940 fs/read_write.c:584
ksys_write+0x147/0x250 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1154 [inline]
free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
free_unref_page_list+0xbe/0x860 mm/page_alloc.c:2475
release_pages+0x1fa0/0x2220 mm/swap.c:1022
__folio_batch_release+0x71/0xe0 mm/swap.c:1042
folio_batch_release include/linux/pagevec.h:83 [inline]
shmem_undo_range+0x5d0/0x1a40 mm/shmem.c:1027
shmem_truncate_range mm/shmem.c:1136 [inline]
shmem_evict_inode+0x273/0xa70 mm/shmem.c:1265
evict+0x486/0x870 fs/inode.c:705
__dentry_kill+0x431/0x650 fs/dcache.c:611
dentry_kill+0xb8/0x290 fs/dcache.c:-1
dput+0xfe/0x1e0 fs/dcache.c:918
__fput+0x5e5/0x970 fs/file_table.c:392
task_work_run+0x1ce/0x250 kernel/task_work.c:239
exit_task_work include/linux/task_work.h:43 [inline]
do_exit+0x90b/0x23c0 kernel/exit.c:883
do_group_exit+0x21b/0x2d0 kernel/exit.c:1024
get_signal+0x12fc/0x1400 kernel/signal.c:2902
arch_do_signal_or_restart+0x96/0x780 arch/x86/kernel/signal.c:310

Memory state around the buggy address:

ffff88805b982f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88805b982f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88805b983000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
^
ffff88805b983080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88805b983100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 3594f306da12 Linux 6.1.147
git tree: linux-6.1.y

console output: https://syzkaller.appspot.com/x/log.txt?x=155c98a2580000

kernel config: https://syzkaller.appspot.com/x/.config?x=2be97b627a5d7554
dashboard link: https://syzkaller.appspot.com/bug?extid=98d90f982e59bdb12f21
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
userspace arch: arm64

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=144ea034580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=135c98a2580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0d2a884e198e/disk-3594f306.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/23d3643328c7/vmlinux-3594f306.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ef83d78711e3/Image-3594f306.gz.xz

mounted in repro: https://storage.googleapis.com/syzbot-assets/382f41eb42bc/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+98d90f...@syzkaller.appspotmail.com

hpfs: You really don't want any checks? You are crazy...

hpfs: hpfs_map_sector(): read error
hpfs: code page support is disabled
==================================================================
BUG: KASAN: use-after-free in strcmp+0xc0/0xf4 lib/string.c:361

Read of size 1 at addr ffff0000e970e8a6 by task syz.0.20/4444

CPU: 0 PID: 4444 Comm: syz.0.20 Not tainted 6.1.147-syzkaller #0

page:00000000ff45aad0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x12970e
flags: 0x5ffc00000000000(node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000000000 fffffc0003a5c3c8 fffffc0003a5c348 0000000000000000

raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:

ffff0000e970e780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff0000e970e800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff0000e970e880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff0000e970e900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff0000e970e980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff

==================================================================
hpfs: hpfs_map_sector(): read error
hpfs: hpfs_map_sector(): read error
hpfs: hpfs_map_sector(): read error
hpfs: hpfs_map_sector(): read error
hpfs: hpfs_map_4sectors(): unaligned read
hpfs: hpfs_map_4sectors(): unaligned read
hpfs: filesystem error: unable to find root dir


---

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: dbcb8d8e4163 Linux 6.6.100
git tree: linux-6.6.y

console output: https://syzkaller.appspot.com/x/log.txt?x=159674f0580000

kernel config: https://syzkaller.appspot.com/x/.config?x=293251cfa8d8100
dashboard link: https://syzkaller.appspot.com/bug?extid=91209a63bd6e8b2608e4
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14f52782580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11aea034580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d0b56817a2c3/disk-dbcb8d8e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f0d646b2f7fa/vmlinux-dbcb8d8e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1e0b752a5011/bzImage-dbcb8d8e.xz

mounted in repro: https://storage.googleapis.com/syzbot-assets/0a0c0ac0a6f7/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+91209a...@syzkaller.appspotmail.com

=======================================================
hpfs: filesystem error: invalid number of hotfixes: 2066844986, used: 2066844985; already mounted read-only

hpfs: filesystem error: improperly stopped
hpfs: You really don't want any checks? You are crazy...
hpfs: hpfs_map_sector(): read error
hpfs: code page support is disabled
==================================================================
BUG: KASAN: use-after-free in strcmp+0x6f/0xb0 lib/string.c:288

Read of size 1 at addr ffff88806bec88a6 by task syz.0.16/5940

CPU: 1 PID: 5940 Comm: syz.0.16 Not tainted 6.6.100-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
<TASK>
dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:364 [inline]
print_report+0xac/0x200 mm/kasan/report.c:466
kasan_report+0x117/0x150 mm/kasan/report.c:579
strcmp+0x6f/0xb0 lib/string.c:288
hpfs_get_ea+0x115/0xda0 fs/hpfs/ea.c:139
hpfs_read_inode+0x19e/0x1010 fs/hpfs/inode.c:63
hpfs_fill_super+0x12d5/0x1ec0 fs/hpfs/super.c:712
mount_bdev+0x22b/0x2d0 fs/super.c:1643
legacy_get_tree+0xea/0x180 fs/fs_context.c:662
vfs_get_tree+0x8c/0x280 fs/super.c:1764
do_new_mount+0x24b/0xa40 fs/namespace.c:3371
do_mount fs/namespace.c:3711 [inline]
__do_sys_mount fs/namespace.c:3920 [inline]
__se_sys_mount+0x2da/0x3c0 fs/namespace.c:3897
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

RIP: 0033:0x7f4af719014a

Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 1a 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 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:00007ffc6e100d38 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffc6e100dc0 RCX: 00007f4af719014a
RDX: 0000200000009e80 RSI: 0000200000009ec0 RDI: 00007ffc6e100d80
RBP: 0000200000009e80 R08: 00007ffc6e100dc0 R09: 0000000000000041

R10: 0000000000000041 R11: 0000000000000246 R12: 0000200000009ec0

R13: 00007ffc6e100d80 R14: 0000000000009e05 R15: 0000200000009f00

</TASK>

The buggy address belongs to the physical page:

page:ffffea0001afb200 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x6bec8
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffff7f(buddy)
raw: 00fff00000000000 ffff88813fffa988 ffffea0001afb608 0000000000000000
raw: 0000000000000001 0000000000000003 00000000ffffff7f 0000000000000000

page dumped because: kasan: bad access detected

page_owner tracks the page as freed
page last allocated via order 0, migratetype Movable, gfp_mask 0x140dca(GFP_HIGHUSER_MOVABLE|__GFP_COMP|__GFP_ZERO), pid 5909, tgid 5909 (sed), ts 80232672028, free_ts 80242281790

set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
prep_new_page mm/page_alloc.c:1561 [inline]
get_page_from_freelist+0x195c/0x19f0 mm/page_alloc.c:3191
__alloc_pages+0x1e3/0x460 mm/page_alloc.c:4457
__folio_alloc+0x10/0x20 mm/page_alloc.c:4489
vma_alloc_folio+0x47a/0x8f0 mm/mempolicy.c:2242

do_anonymous_page mm/memory.c:4149 [inline]
do_pte_missing mm/memory.c:3686 [inline]
handle_pte_fault mm/memory.c:5025 [inline]
__handle_mm_fault mm/memory.c:5166 [inline]
handle_mm_fault+0x1a38/0x4920 mm/memory.c:5331
do_user_addr_fault+0xad0/0x12e0 arch/x86/mm/fault.c:1324
handle_page_fault arch/x86/mm/fault.c:1465 [inline]
exc_page_fault+0x67/0x110 arch/x86/mm/fault.c:1521
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:608

page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1154 [inline]
free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
free_unref_page_list+0xbe/0x860 mm/page_alloc.c:2475
release_pages+0x1fa0/0x2220 mm/swap.c:1022

tlb_batch_pages_flush mm/mmu_gather.c:98 [inline]
tlb_flush_mmu_free mm/mmu_gather.c:293 [inline]
tlb_flush_mmu+0x368/0x4f0 mm/mmu_gather.c:300
tlb_finish_mmu+0xc3/0x1d0 mm/mmu_gather.c:392
exit_mmap+0x3f0/0xb50 mm/mmap.c:3311
__mmput+0x118/0x3c0 kernel/fork.c:1355
exit_mm+0x1da/0x2c0 kernel/exit.c:569
do_exit+0x88e/0x23c0 kernel/exit.c:870
do_group_exit+0x21b/0x2d0 kernel/exit.c:1024
__do_sys_exit_group kernel/exit.c:1035 [inline]
__se_sys_exit_group kernel/exit.c:1033 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1033

do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

Memory state around the buggy address:

ffff88806bec8780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88806bec8800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88806bec8880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff88806bec8900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88806bec8980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================