[v6.6] KASAN: use-after-free Read in sysv_new_inode

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 59a2de10b81a Linux 6.6.97
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1216818c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=ac0b29aca872266f
dashboard link: https://syzkaller.appspot.com/bug?extid=9231067e328b56b281ac
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/32864b54a55c/disk-59a2de10.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b0bbe4ada642/vmlinux-59a2de10.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9e3fe91e14c2/bzImage-59a2de10.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+923106...@syzkaller.appspotmail.com

syz.3.553: attempt to access beyond end of device
loop3: rw=0, sector=6491536, nr_sectors = 2 limit=128
Buffer I/O error on dev loop3, logical block 3245768, async page read
==================================================================
BUG: KASAN: use-after-free in sysv_new_inode+0x10c5/0x1270 fs/sysv/ialloc.c:153
Read of size 2 at addr ffff88805811d1ce by task syz.3.553/7930

CPU: 0 PID: 7930 Comm: syz.3.553 Not tainted 6.6.97-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/0x230 mm/kasan/report.c:475
kasan_report+0x117/0x150 mm/kasan/report.c:588
sysv_new_inode+0x10c5/0x1270 fs/sysv/ialloc.c:153
sysv_mknod+0x4e/0xe0 fs/sysv/namei.c:53
lookup_open fs/namei.c:3488 [inline]
open_last_lookups fs/namei.c:3556 [inline]
path_openat+0x1277/0x3190 fs/namei.c:3786
do_filp_open+0x1c5/0x3d0 fs/namei.c:3816
do_sys_openat2+0x12c/0x1c0 fs/open.c:1419
do_sys_open fs/open.c:1434 [inline]
__do_sys_openat fs/open.c:1450 [inline]
__se_sys_openat fs/open.c:1445 [inline]
__x64_sys_openat+0x139/0x160 fs/open.c:1445
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: 0033:0x7fd77f58e929
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:00007fd780485038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fd77f7b5fa0 RCX: 00007fd77f58e929
RDX: 0000000000101042 RSI: 0000200000000180 RDI: ffffffffffffff9c
RBP: 00007fd77f610b39 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000000001b6 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fd77f7b5fa0 R15: 00007ffe8bd97848
</TASK>

The buggy address belongs to the physical page:
page:ffffea0001604740 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x5811d
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 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 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 7893, tgid 7892 (syz.0.546), ts 268316706453, free_ts 269855012158
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
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87

Memory state around the buggy address:
ffff88805811d080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88805811d100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88805811d180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff88805811d200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88805811d280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 59a2de10b81a Linux 6.6.97
git tree: linux-6.6.y

console output: https://syzkaller.appspot.com/x/log.txt?x=116f5d82580000

kernel config: https://syzkaller.appspot.com/x/.config?x=ac0b29aca872266f
dashboard link: https://syzkaller.appspot.com/bug?extid=9231067e328b56b281ac
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=10d087d4580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13a6d0f0580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/32864b54a55c/disk-59a2de10.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b0bbe4ada642/vmlinux-59a2de10.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9e3fe91e14c2/bzImage-59a2de10.xz

mounted in repro: https://storage.googleapis.com/syzbot-assets/eaee549275ea/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+923106...@syzkaller.appspotmail.com

syz.0.16[5944]: memfd_create() called without MFD_EXEC or MFD_NOEXEC_SEAL set
loop0: detected capacity change from 0 to 128
VFS: Found a Xenix FS (block size = 1024) on device loop0
syz.0.16: attempt to access beyond end of device
loop0: rw=0, sector=6491536, nr_sectors = 2 limit=128
Buffer I/O error on dev loop0, logical block 3245768, async page read

==================================================================
BUG: KASAN: use-after-free in sysv_new_inode+0x10c5/0x1270 fs/sysv/ialloc.c:153

Read of size 2 at addr ffff88806d2b41ce by task syz.0.16/5944

CPU: 0 PID: 5944 Comm: syz.0.16 Not tainted 6.6.97-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/0x230 mm/kasan/report.c:475
kasan_report+0x117/0x150 mm/kasan/report.c:588
sysv_new_inode+0x10c5/0x1270 fs/sysv/ialloc.c:153
sysv_mknod+0x4e/0xe0 fs/sysv/namei.c:53
lookup_open fs/namei.c:3488 [inline]
open_last_lookups fs/namei.c:3556 [inline]
path_openat+0x1277/0x3190 fs/namei.c:3786
do_filp_open+0x1c5/0x3d0 fs/namei.c:3816
do_sys_openat2+0x12c/0x1c0 fs/open.c:1419
do_sys_open fs/open.c:1434 [inline]
__do_sys_openat fs/open.c:1450 [inline]
__se_sys_openat fs/open.c:1445 [inline]
__x64_sys_openat+0x139/0x160 fs/open.c:1445
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: 0033:0x7f67ff58e929

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:00007ffd766a0a38 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f67ff7b5fa0 RCX: 00007f67ff58e929

RDX: 0000000000101042 RSI: 0000200000000180 RDI: ffffffffffffff9c

RBP: 00007f67ff610b39 R08: 0000000000000000 R09: 0000000000000000

R10: 00000000000001b6 R11: 0000000000000246 R12: 0000000000000000

R13: 00007f67ff7b5fa0 R14: 00007f67ff7b5fa0 R15: 0000000000000004

</TASK>

The buggy address belongs to the physical page:

page:ffffea0001b4ad00 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x6d2b4
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffff7f(buddy)
raw: 00fff00000000000 ffffea0001b40d08 ffffea0001b30308 0000000000000000
raw: 0000000000000001 0000000000000002 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 5931, tgid 5931 (rm), ts 100836855443, free_ts 100872289474

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+0x738/0x12e0 arch/x86/mm/fault.c:1373
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:

ffff88806d2b4080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88806d2b4100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88806d2b4180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff88806d2b4200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88806d2b4280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
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