[PATCH] f2fs: fix to avoid panic in f2fs_evict_inode

From: Chao Yu
Date: Thu Jul 03 2025 - 02:34:52 EST

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As syzbot [1] reported as below:

R10: 0000000000000100 R11: 0000000000000206 R12: 00007ffe17473450
R13: 00007f28b1c10854 R14: 000000000000dae5 R15: 00007ffe17474520
</TASK>
---[ end trace 0000000000000000 ]---
==================================================================
BUG: KASAN: use-after-free in __list_del_entry_valid+0xa6/0x130 lib/list_debug.c:62
Read of size 8 at addr ffff88812d962278 by task syz-executor/564

CPU: 1 PID: 564 Comm: syz-executor Tainted: G W 6.1.129-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
<TASK>
__dump_stack+0x21/0x24 lib/dump_stack.c:88
dump_stack_lvl+0xee/0x158 lib/dump_stack.c:106
print_address_description+0x71/0x210 mm/kasan/report.c:316
print_report+0x4a/0x60 mm/kasan/report.c:427
kasan_report+0x122/0x150 mm/kasan/report.c:531
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:351
__list_del_entry_valid+0xa6/0x130 lib/list_debug.c:62
__list_del_entry include/linux/list.h:134 [inline]
list_del_init include/linux/list.h:206 [inline]
f2fs_inode_synced+0xf7/0x2e0 fs/f2fs/super.c:1531
f2fs_update_inode+0x74/0x1c40 fs/f2fs/inode.c:585
f2fs_update_inode_page+0x137/0x170 fs/f2fs/inode.c:703
f2fs_write_inode+0x4ec/0x770 fs/f2fs/inode.c:731
write_inode fs/fs-writeback.c:1460 [inline]
__writeback_single_inode+0x4a0/0xab0 fs/fs-writeback.c:1677
writeback_single_inode+0x221/0x8b0 fs/fs-writeback.c:1733
sync_inode_metadata+0xb6/0x110 fs/fs-writeback.c:2789
f2fs_sync_inode_meta+0x16d/0x2a0 fs/f2fs/checkpoint.c:1159
block_operations fs/f2fs/checkpoint.c:1269 [inline]
f2fs_write_checkpoint+0xca3/0x2100 fs/f2fs/checkpoint.c:1658
kill_f2fs_super+0x231/0x390 fs/f2fs/super.c:4668
deactivate_locked_super+0x98/0x100 fs/super.c:332
deactivate_super+0xaf/0xe0 fs/super.c:363
cleanup_mnt+0x45f/0x4e0 fs/namespace.c:1186
__cleanup_mnt+0x19/0x20 fs/namespace.c:1193
task_work_run+0x1c6/0x230 kernel/task_work.c:203
exit_task_work include/linux/task_work.h:39 [inline]
do_exit+0x9fb/0x2410 kernel/exit.c:871
do_group_exit+0x210/0x2d0 kernel/exit.c:1021
__do_sys_exit_group kernel/exit.c:1032 [inline]
__se_sys_exit_group kernel/exit.c:1030 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1030
x64_sys_call+0x7b4/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:232
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f28b1b8e169
Code: Unable to access opcode bytes at 0x7f28b1b8e13f.
RSP: 002b:00007ffe174710a8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007f28b1c10879 RCX: 00007f28b1b8e169
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000001
RBP: 0000000000000002 R08: 00007ffe1746ee47 R09: 00007ffe17472360
R10: 0000000000000009 R11: 0000000000000246 R12: 00007ffe17472360
R13: 00007f28b1c10854 R14: 000000000000dae5 R15: 00007ffe17474520
</TASK>

Allocated by task 569:
kasan_save_stack mm/kasan/common.c:45 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
kasan_save_alloc_info+0x25/0x30 mm/kasan/generic.c:505
__kasan_slab_alloc+0x72/0x80 mm/kasan/common.c:328
kasan_slab_alloc include/linux/kasan.h:201 [inline]
slab_post_alloc_hook+0x4f/0x2c0 mm/slab.h:737
slab_alloc_node mm/slub.c:3398 [inline]
slab_alloc mm/slub.c:3406 [inline]
__kmem_cache_alloc_lru mm/slub.c:3413 [inline]
kmem_cache_alloc_lru+0x104/0x220 mm/slub.c:3429
alloc_inode_sb include/linux/fs.h:3245 [inline]
f2fs_alloc_inode+0x2d/0x340 fs/f2fs/super.c:1419
alloc_inode fs/inode.c:261 [inline]
iget_locked+0x186/0x880 fs/inode.c:1373
f2fs_iget+0x55/0x4c60 fs/f2fs/inode.c:483
f2fs_lookup+0x366/0xab0 fs/f2fs/namei.c:487
__lookup_slow+0x2a3/0x3d0 fs/namei.c:1690
lookup_slow+0x57/0x70 fs/namei.c:1707
walk_component+0x2e6/0x410 fs/namei.c:1998
lookup_last fs/namei.c:2455 [inline]
path_lookupat+0x180/0x490 fs/namei.c:2479
filename_lookup+0x1f0/0x500 fs/namei.c:2508
vfs_statx+0x10b/0x660 fs/stat.c:229
vfs_fstatat fs/stat.c:267 [inline]
vfs_lstat include/linux/fs.h:3424 [inline]
__do_sys_newlstat fs/stat.c:423 [inline]
__se_sys_newlstat+0xd5/0x350 fs/stat.c:417
__x64_sys_newlstat+0x5b/0x70 fs/stat.c:417
x64_sys_call+0x393/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:7
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 13:
kasan_save_stack mm/kasan/common.c:45 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
kasan_save_free_info+0x31/0x50 mm/kasan/generic.c:516
____kasan_slab_free+0x132/0x180 mm/kasan/common.c:236
__kasan_slab_free+0x11/0x20 mm/kasan/common.c:244
kasan_slab_free include/linux/kasan.h:177 [inline]
slab_free_hook mm/slub.c:1724 [inline]
slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1750
slab_free mm/slub.c:3661 [inline]
kmem_cache_free+0x12d/0x2a0 mm/slub.c:3683
f2fs_free_inode+0x24/0x30 fs/f2fs/super.c:1562
i_callback+0x4c/0x70 fs/inode.c:250
rcu_do_batch+0x503/0xb80 kernel/rcu/tree.c:2297
rcu_core+0x5a2/0xe70 kernel/rcu/tree.c:2557
rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2574
handle_softirqs+0x178/0x500 kernel/softirq.c:578
run_ksoftirqd+0x28/0x30 kernel/softirq.c:945
smpboot_thread_fn+0x45a/0x8c0 kernel/smpboot.c:164
kthread+0x270/0x310 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

Last potentially related work creation:
kasan_save_stack+0x3a/0x60 mm/kasan/common.c:45
__kasan_record_aux_stack+0xb6/0xc0 mm/kasan/generic.c:486
kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:496
call_rcu+0xd4/0xf70 kernel/rcu/tree.c:2845
destroy_inode fs/inode.c:316 [inline]
evict+0x7da/0x870 fs/inode.c:720
iput_final fs/inode.c:1834 [inline]
iput+0x62b/0x830 fs/inode.c:1860
do_unlinkat+0x356/0x540 fs/namei.c:4397
__do_sys_unlink fs/namei.c:4438 [inline]
__se_sys_unlink fs/namei.c:4436 [inline]
__x64_sys_unlink+0x49/0x50 fs/namei.c:4436
x64_sys_call+0x958/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:88
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff88812d961f20
which belongs to the cache f2fs_inode_cache of size 1200
The buggy address is located 856 bytes inside of
1200-byte region [ffff88812d961f20, ffff88812d9623d0)

The buggy address belongs to the physical page:
page:ffffea0004b65800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x12d960
head:ffffea0004b65800 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 0000000000000000 dead000000000122 ffff88810a94c500
raw: 0000000000000000 00000000800c000c 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Reclaimable, gfp_mask 0x1d2050(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL|__GFP_RECLAIMABLE), pid 569, tgid 568 (syz.2.16), ts 55943246141, free_ts 0
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1d0/0x1f0 mm/page_alloc.c:2532
prep_new_page mm/page_alloc.c:2539 [inline]
get_page_from_freelist+0x2e63/0x2ef0 mm/page_alloc.c:4328
__alloc_pages+0x235/0x4b0 mm/page_alloc.c:5605
alloc_slab_page include/linux/gfp.h:-1 [inline]
allocate_slab mm/slub.c:1939 [inline]
new_slab+0xec/0x4b0 mm/slub.c:1992
___slab_alloc+0x6f6/0xb50 mm/slub.c:3180
__slab_alloc+0x5e/0xa0 mm/slub.c:3279
slab_alloc_node mm/slub.c:3364 [inline]
slab_alloc mm/slub.c:3406 [inline]
__kmem_cache_alloc_lru mm/slub.c:3413 [inline]
kmem_cache_alloc_lru+0x13f/0x220 mm/slub.c:3429
alloc_inode_sb include/linux/fs.h:3245 [inline]
f2fs_alloc_inode+0x2d/0x340 fs/f2fs/super.c:1419
alloc_inode fs/inode.c:261 [inline]
iget_locked+0x186/0x880 fs/inode.c:1373
f2fs_iget+0x55/0x4c60 fs/f2fs/inode.c:483
f2fs_fill_super+0x3ad7/0x6bb0 fs/f2fs/super.c:4293
mount_bdev+0x2ae/0x3e0 fs/super.c:1443
f2fs_mount+0x34/0x40 fs/f2fs/super.c:4642
legacy_get_tree+0xea/0x190 fs/fs_context.c:632
vfs_get_tree+0x89/0x260 fs/super.c:1573
do_new_mount+0x25a/0xa20 fs/namespace.c:3056
page_owner free stack trace missing

Memory state around the buggy address:
ffff88812d962100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88812d962180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88812d962200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88812d962280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88812d962300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

[1] https://syzkaller.appspot.com/x/report.txt?x=13448368580000

This bug can be reproduced w/ the reproducer [2], once we enable
CONFIG_F2FS_CHECK_FS config, the reproducer will trigger panic as below,
so the direct reason of this bug is the same as the one below patch [3]
fixed.

kernel BUG at fs/f2fs/inode.c:857!
RIP: 0010:f2fs_evict_inode+0x1204/0x1a20
Call Trace:
<TASK>
evict+0x32a/0x7a0
do_unlinkat+0x37b/0x5b0
__x64_sys_unlink+0xad/0x100
do_syscall_64+0x5a/0xb0
entry_SYSCALL_64_after_hwframe+0x6e/0xd8
RIP: 0010:f2fs_evict_inode+0x1204/0x1a20

[2] https://syzkaller.appspot.com/x/repro.c?x=17495ccc580000
[3] https://lore.kernel.org/linux-f2fs-devel/20250702120321.1080759-1-chao@xxxxxxxxxx

Tracepoints before panic:

f2fs_unlink_enter: dev = (7,0), dir ino = 3, i_size = 4096, i_blocks = 8, name = file1
f2fs_unlink_exit: dev = (7,0), ino = 7, ret = 0
f2fs_evict_inode: dev = (7,0), ino = 7, pino = 3, i_mode = 0x81ed, i_size = 10, i_nlink = 0, i_blocks = 0, i_advise = 0x0
f2fs_truncate_node: dev = (7,0), ino = 7, nid = 8, block_address = 0x3c05

f2fs_unlink_enter: dev = (7,0), dir ino = 3, i_size = 4096, i_blocks = 8, name = file3
f2fs_unlink_exit: dev = (7,0), ino = 8, ret = 0
f2fs_evict_inode: dev = (7,0), ino = 8, pino = 3, i_mode = 0x81ed, i_size = 9000, i_nlink = 0, i_blocks = 24, i_advise = 0x4
f2fs_truncate: dev = (7,0), ino = 8, pino = 3, i_mode = 0x81ed, i_size = 0, i_nlink = 0, i_blocks = 24, i_advise = 0x4
f2fs_truncate_blocks_enter: dev = (7,0), ino = 8, i_size = 0, i_blocks = 24, start file offset = 0
f2fs_truncate_blocks_exit: dev = (7,0), ino = 8, ret = -2

The root cause is: in the fuzzed image, dnode #8 belongs to inode #7,
after inode #7 eviction, dnode #8 was dropped.

However there is dirent that has ino #8, so, once we unlink file3, in
f2fs_evict_inode(), both f2fs_truncate() and f2fs_update_inode_page()
will fail due to we can not load node #8, result in we missed to call
f2fs_inode_synced() to clear inode dirty status.

Let's fix this by calling f2fs_inode_synced() in error path of
f2fs_evict_inode().

PS: As I verified, the reproducer [2] can trigger this bug in v6.1.129,
but it failed in v6.16-rc4, this is because the testcase will stop due to
other corruption has been detected by f2fs:

F2FS-fs (loop0): inconsistent node block, node_type:2, nid:8, node_footer[nid:8,ino:8,ofs:0,cpver:5013063228981249506,blkaddr:15366]
F2FS-fs (loop0): f2fs_lookup: inode (ino=9) has zero i_nlink

Cc: stable@xxxxxxxxxx
Closes: https://syzkaller.appspot.com/x/report.txt?x=13448368580000
Signed-off-by: Chao Yu <chao@xxxxxxxxxx>
---
fs/f2fs/inode.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
index d3c6f3202b69..fc774de1c752 100644
--- a/fs/f2fs/inode.c
+++ b/fs/f2fs/inode.c
@@ -933,6 +933,19 @@ void f2fs_evict_inode(struct inode *inode)
f2fs_update_inode_page(inode);
if (dquot_initialize_needed(inode))
set_sbi_flag(sbi, SBI_QUOTA_NEED_REPAIR);
+
+ /*
+ * If both f2fs_truncate() and f2fs_update_inode_page() failed
+ * due to fuzzed corrupted inode, call f2fs_inode_synced() to
+ * avoid triggering later f2fs_bug_on().
+ */
+ if (is_inode_flag_set(inode, FI_DIRTY_INODE)) {
+ f2fs_warn(sbi,
+ "f2fs_evict_inode: inode is dirty, ino:%lu",
+ inode->i_ino);
+ f2fs_inode_synced(inode);
+ set_sbi_flag(sbi, SBI_NEED_FSCK);
+ }
}
if (freeze_protected)
sb_end_intwrite(inode->i_sb);
--
2.49.0

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