[syzbot] [overlayfs?] KASAN: slab-use-after-free Read in ovl_dentry_update_reval

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4f5e5092fdbf Merge tag 'net-6.8-rc5' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1143fa78180000
kernel config: https://syzkaller.appspot.com/x/.config?x=cb86c5ad8597e08a
dashboard link: https://syzkaller.appspot.com/bug?extid=316db8a1191938280eb6
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: i386

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-4f5e5092.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f8b1959c3264/vmlinux-4f5e5092.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4dd38747bfa8/bzImage-4f5e5092.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+316db8...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in ovl_dentry_remote fs/overlayfs/util.c:162 [inline]
BUG: KASAN: slab-use-after-free in ovl_dentry_update_reval+0xd2/0xf0 fs/overlayfs/util.c:167
Read of size 4 at addr ffff888028839b90 by task syz-executor.1/16906

CPU: 0 PID: 16906 Comm: syz-executor.1 Not tainted 6.8.0-rc4-syzkaller-00180-g4f5e5092fdbf #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:377 [inline]
print_report+0xc4/0x620 mm/kasan/report.c:488
kasan_report+0xda/0x110 mm/kasan/report.c:601
ovl_dentry_remote fs/overlayfs/util.c:162 [inline]
ovl_dentry_update_reval+0xd2/0xf0 fs/overlayfs/util.c:167
ovl_link_up fs/overlayfs/copy_up.c:610 [inline]
ovl_copy_up_one+0x20fa/0x3490 fs/overlayfs/copy_up.c:1170
ovl_copy_up_flags+0x18d/0x200 fs/overlayfs/copy_up.c:1223
ovl_nlink_start+0x372/0x450 fs/overlayfs/util.c:1153
ovl_do_remove+0x171/0xde0 fs/overlayfs/dir.c:893
vfs_unlink+0x2fb/0x910 fs/namei.c:4334
do_unlinkat+0x5c0/0x750 fs/namei.c:4398
__do_sys_unlink fs/namei.c:4446 [inline]
__se_sys_unlink fs/namei.c:4444 [inline]
__ia32_sys_unlink+0xc7/0x110 fs/namei.c:4444
do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
__do_fast_syscall_32+0x7c/0x120 arch/x86/entry/common.c:321
do_fast_syscall_32+0x33/0x80 arch/x86/entry/common.c:346
entry_SYSENTER_compat_after_hwframe+0x7c/0x86
RIP: 0023:0xf7341579
Code: b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
RSP: 002b:00000000f5f3b5ac EFLAGS: 00000292 ORIG_RAX: 000000000000000a
RAX: ffffffffffffffda RBX: 0000000020000200 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000292 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>

Allocated by task 16906:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
unpoison_slab_object mm/kasan/common.c:314 [inline]
__kasan_slab_alloc+0x89/0x90 mm/kasan/common.c:340
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]
kmem_cache_alloc_lru+0x140/0x700 mm/slub.c:3879
__d_alloc+0x35/0x8c0 fs/dcache.c:1624
d_alloc+0x4a/0x1e0 fs/dcache.c:1704
d_alloc_parallel+0xe9/0x12c0 fs/dcache.c:2462
__lookup_slow+0x194/0x460 fs/namei.c:1678
lookup_one+0x185/0x1c0 fs/namei.c:2785
ovl_lookup_upper fs/overlayfs/overlayfs.h:401 [inline]
ovl_link_up fs/overlayfs/copy_up.c:599 [inline]
ovl_copy_up_one+0x104e/0x3490 fs/overlayfs/copy_up.c:1170
ovl_copy_up_flags+0x18d/0x200 fs/overlayfs/copy_up.c:1223
ovl_nlink_start+0x372/0x450 fs/overlayfs/util.c:1153
ovl_do_remove+0x171/0xde0 fs/overlayfs/dir.c:893
vfs_unlink+0x2fb/0x910 fs/namei.c:4334
do_unlinkat+0x5c0/0x750 fs/namei.c:4398
__do_sys_unlink fs/namei.c:4446 [inline]
__se_sys_unlink fs/namei.c:4444 [inline]
__ia32_sys_unlink+0xc7/0x110 fs/namei.c:4444
do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
__do_fast_syscall_32+0x7c/0x120 arch/x86/entry/common.c:321
do_fast_syscall_32+0x33/0x80 arch/x86/entry/common.c:346
entry_SYSENTER_compat_after_hwframe+0x7c/0x86

Freed by task 109:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
kasan_save_free_info+0x3f/0x60 mm/kasan/generic.c:640
poison_slab_object mm/kasan/common.c:241 [inline]
__kasan_slab_free+0x121/0x1c0 mm/kasan/common.c:257
kasan_slab_free include/linux/kasan.h:184 [inline]
slab_free_hook mm/slub.c:2121 [inline]
slab_free mm/slub.c:4299 [inline]
kmem_cache_free+0x129/0x360 mm/slub.c:4363
rcu_do_batch kernel/rcu/tree.c:2190 [inline]
rcu_core+0x819/0x1680 kernel/rcu/tree.c:2465
__do_softirq+0x21c/0x8e7 kernel/softirq.c:553

Last potentially related work creation:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
__kasan_record_aux_stack+0xba/0x110 mm/kasan/generic.c:586
__call_rcu_common.constprop.0+0x9a/0x7c0 kernel/rcu/tree.c:2715
dentry_free+0xc2/0x160 fs/dcache.c:376
__dentry_kill+0x498/0x600 fs/dcache.c:622
shrink_kill fs/dcache.c:1048 [inline]
shrink_dentry_list+0x140/0x5d0 fs/dcache.c:1075
prune_dcache_sb+0xeb/0x150 fs/dcache.c:1156
super_cache_scan+0x32a/0x550 fs/super.c:221
do_shrink_slab+0x426/0x1120 mm/shrinker.c:435
shrink_slab_memcg mm/shrinker.c:548 [inline]
shrink_slab+0xa87/0x1310 mm/shrinker.c:626
shrink_one+0x493/0x7b0 mm/vmscan.c:4767
shrink_many mm/vmscan.c:4828 [inline]
lru_gen_shrink_node mm/vmscan.c:4929 [inline]
shrink_node+0x21d0/0x3790 mm/vmscan.c:5888
kswapd_shrink_node mm/vmscan.c:6693 [inline]
balance_pgdat+0x9d2/0x1a90 mm/vmscan.c:6883
kswapd+0x5be/0xc00 mm/vmscan.c:7143
kthread+0x2c6/0x3b0 kernel/kthread.c:388
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:242

The buggy address belongs to the object at ffff888028839b90
which belongs to the cache dentry of size 312
The buggy address is located 0 bytes inside of
freed 312-byte region [ffff888028839b90, ffff888028839cc8)

The buggy address belongs to the physical page:
page:ffffea0000a20e00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x28838
head:ffffea0000a20e00 order:1 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff888020749431
ksm flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff8880162cf400 ffffea0000a28d00 dead000000000003
raw: 0000000000000000 0000000080140014 00000001ffffffff ffff888020749431
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Reclaimable, gfp_mask 0xd20d0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_RECLAIMABLE), pid 4679, tgid 4679 (udevd), ts 34753908780, free_ts 0
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x2d4/0x350 mm/page_alloc.c:1533
prep_new_page mm/page_alloc.c:1540 [inline]
get_page_from_freelist+0xa28/0x3780 mm/page_alloc.c:3311
__alloc_pages+0x22f/0x2440 mm/page_alloc.c:4567
__alloc_pages_node include/linux/gfp.h:238 [inline]
alloc_pages_node include/linux/gfp.h:261 [inline]
alloc_slab_page mm/slub.c:2190 [inline]
allocate_slab mm/slub.c:2354 [inline]
new_slab+0xcc/0x3a0 mm/slub.c:2407
___slab_alloc+0x4b0/0x1780 mm/slub.c:3540
__slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3625
__slab_alloc_node mm/slub.c:3678 [inline]
slab_alloc_node mm/slub.c:3850 [inline]
kmem_cache_alloc_lru+0x37b/0x700 mm/slub.c:3879
__d_alloc+0x35/0x8c0 fs/dcache.c:1624
d_alloc+0x4a/0x1e0 fs/dcache.c:1704
lookup_one_qstr_excl+0xcb/0x190 fs/namei.c:1604
do_renameat2+0x5ae/0xdc0 fs/namei.c:4986
__do_sys_rename fs/namei.c:5083 [inline]
__se_sys_rename fs/namei.c:5081 [inline]
__x64_sys_rename+0x81/0xa0 fs/namei.c:5081
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xd5/0x270 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x6f/0x77
page_owner free stack trace missing

Memory state around the buggy address:
ffff888028839a80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888028839b00: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
>ffff888028839b80: fc fc fa fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888028839c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888028839c80: fb fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess), 2 bytes skipped:
0: 10 06 adc %al,(%rsi)
2: 03 74 b4 01 add 0x1(%rsp,%rsi,4),%esi
6: 10 07 adc %al,(%rdi)
8: 03 74 b0 01 add 0x1(%rax,%rsi,4),%esi
c: 10 08 adc %cl,(%rax)
e: 03 74 d8 01 add 0x1(%rax,%rbx,8),%esi
1e: 00 51 52 add %dl,0x52(%rcx)
21: 55 push %rbp
22: 89 e5 mov %esp,%ebp
24: 0f 34 sysenter
26: cd 80 int $0x80
* 28: 5d pop %rbp <-- trapping instruction
29: 5a pop %rdx
2a: 59 pop %rcx
2b: c3 ret
2c: 90 nop
2d: 90 nop
2e: 90 nop
2f: 90 nop
30: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi
37: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi


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