[syzbot] [f2fs?] kernel BUG in clear_inode (5)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dee65f79364c Merge tag 'lsm-pr-20260202' of git://git.kern..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1639fbfa580000
kernel config: https://syzkaller.appspot.com/x/.config?x=151a39927f1e10b4
dashboard link: https://syzkaller.appspot.com/bug?extid=fc026e87558558f75c00
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=114fb322580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1245fc5a580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d5a48068ae28/disk-dee65f79.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2c254f049b04/vmlinux-dee65f79.xz
kernel image: https://storage.googleapis.com/syzbot-assets/12b280dac533/bzImage-dee65f79.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/bce313ec1951/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=164fb322580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fc026e...@syzkaller.appspotmail.com

F2FS-fs (loop0): Wrong SSA boundary, start(3584) end(4096) blocks(3072)
F2FS-fs (loop0): Can't find valid F2FS filesystem in 1th superblock
F2FS-fs (loop0): Image doesn't support compression
F2FS-fs (loop0): invalid crc value
------------[ cut here ]------------
kernel BUG at fs/inode.c:782!
Oops: invalid opcode: 0000 [#1] SMP KASAN PTI
CPU: 1 UID: 0 PID: 6061 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
RIP: 0010:clear_inode+0x19a/0x1c0 fs/inode.c:782
Code: 4c 89 f7 e8 08 2f eb ff e9 5a ff ff ff 44 89 f1 80 e1 07 80 c1 03 38 c1 7c a2 4c 89 f7 e8 de 2f eb ff eb 98 e8 47 c7 86 ff 90 <0f> 0b e8 3f c7 86 ff 90 0f 0b e8 37 c7 86 ff 90 0f 0b e8 2f c7 86
RSP: 0018:ffffc90003e17850 EFLAGS: 00010293
RAX: ffffffff823c6d29 RBX: ffff888057a99310 RCX: ffff88802b1edac0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90003e179c0 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1e8fbef R12: dffffc0000000000
R13: 1ffff920007c2f1c R14: ffff888057a99568 R15: 0000000000000001
FS: 000055557a53e500(0000) GS:ffff8881266c9000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fff6ffc5bbc CR3: 0000000034a72000 CR4: 00000000003526f0
Call Trace:
<TASK>
evict+0x61e/0xb10 fs/inode.c:837
f2fs_fill_super+0x54e4/0x6e30 fs/f2fs/super.c:5147
get_tree_bdev_flags+0x431/0x4f0 fs/super.c:1691
vfs_get_tree+0x92/0x2a0 fs/super.c:1751
fc_mount fs/namespace.c:1199 [inline]
do_new_mount_fc fs/namespace.c:3636 [inline]
do_new_mount+0x329/0xa50 fs/namespace.c:3712
do_mount fs/namespace.c:4035 [inline]
__do_sys_mount fs/namespace.c:4224 [inline]
__se_sys_mount+0x31d/0x420 fs/namespace.c:4201
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff95c0cc14a
Code: 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff c3 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd4f028d88 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffd4f028e10 RCX: 00007ff95c0cc14a
RDX: 0000200000000140 RSI: 00002000000001c0 RDI: 00007ffd4f028dd0
RBP: 0000200000000140 R08: 00007ffd4f028e10 R09: 0000000000000008
R10: 0000000000000008 R11: 0000000000000246 R12: 00002000000001c0
R13: 00007ffd4f028dd0 R14: 0000000000005548 R15: 0000200000000200
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:clear_inode+0x19a/0x1c0 fs/inode.c:782
Code: 4c 89 f7 e8 08 2f eb ff e9 5a ff ff ff 44 89 f1 80 e1 07 80 c1 03 38 c1 7c a2 4c 89 f7 e8 de 2f eb ff eb 98 e8 47 c7 86 ff 90 <0f> 0b e8 3f c7 86 ff 90 0f 0b e8 37 c7 86 ff 90 0f 0b e8 2f c7 86
RSP: 0018:ffffc90003e17850 EFLAGS: 00010293
RAX: ffffffff823c6d29 RBX: ffff888057a99310 RCX: ffff88802b1edac0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90003e179c0 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1e8fbef R12: dffffc0000000000
R13: 1ffff920007c2f1c R14: ffff888057a99568 R15: 0000000000000001
FS: 000055557a53e500(0000) GS:ffff8881266c9000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fff6ffc5bbc CR3: 0000000034a72000 CR4: 00000000003526f0


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Subject: #syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git f14faaf3a1fb3b9e4cf2e56269711fb85fba9458
Author: dman...@yandex.ru

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git f14faaf3a1fb3b9e4cf2e56269711fb85fba9458

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+fc026e...@syzkaller.appspotmail.com
Tested-by: syzbot+fc026e...@syzkaller.appspotmail.com

Tested on:

commit: f14faaf3 Merge tag 'tsm-fixes-for-6.19' of git://git.k..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=1302c7fa580000

kernel config: https://syzkaller.appspot.com/x/.config?x=151a39927f1e10b4
dashboard link: https://syzkaller.appspot.com/bug?extid=fc026e87558558f75c00
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

patch: https://syzkaller.appspot.com/x/patch.diff?x=124b0a52580000

Note: testing is done by a robot and is best-effort only.

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For archival purposes, forwarding an incoming command email to
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Subject: Re: [syzbot] [f2fs?] kernel BUG in clear_inode (5)
Author: kth...@gmail.com

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
index 38b8994bc1b2..914a0966a1c5 100644
--- a/fs/f2fs/inode.c
+++ b/fs/f2fs/inode.c
@@ -1001,6 +1001,13 @@ void f2fs_evict_inode(struct inode *inode)
out_clear:
fscrypt_put_encryption_info(inode);
fsverity_cleanup_inode(inode);
+ /*
+ * Pages in inode's data mapping may have been re-added during
+ * eviction, e.g. by f2fs_convert_inline_inode() called from
+ * f2fs_truncate(). Truncate them again before clear_inode()
+ * which expects nrpages == 0.
+ */
+ truncate_inode_pages_final(&inode->i_data);
clear_inode(inode);
}

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Subject: Re: [syzbot] [f2fs?] kernel BUG in clear_inode (5)
Author: kth...@gmail.com

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c

--- a/fs/f2fs/inode.c
+++ b/fs/f2fs/inode.c
@@ -1007,6 +1007,13 @@ void f2fs_evict_inode(struct inode *inode)
out_clear:
fscrypt_put_encryption_info(inode);

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Subject: Re: [syzbot] [f2fs?] kernel BUG in clear_inode

Author: kth...@gmail.com

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
index 0a1052d5ee62..92fcadf6d2cc 100644
--- a/fs/f2fs/inline.c
+++ b/fs/f2fs/inline.c
@@ -53,8 +53,8 @@ bool f2fs_sanity_check_inline_data(struct inode *inode, struct folio *ifolio)
if (!f2fs_has_inline_data(inode))
return false;

- if (inode_has_blocks(inode, ifolio))
- return false;
+ if (!f2fs_exist_data(inode) && inode_has_blocks(inode, ifolio))
+ return true;

if (!support_inline_data(inode))
return true;
@@ -142,6 +142,17 @@ int f2fs_read_inline_data(struct inode *inode, struct folio *folio)
return 0;
}

+static void f2fs_clear_inline_inode(struct dnode_of_data *dn)
+{
+ f2fs_folio_wait_writeback(dn->inode_folio, NODE, true, true);
+ clear_inode_flag(dn->inode, FI_DATA_EXIST);
+ clear_inode_flag(dn->inode, FI_INLINE_DATA);
+ set_raw_inline(dn->inode, F2FS_INODE(dn->inode_folio));
+ folio_mark_dirty(dn->inode_folio);
+ folio_clear_f2fs_inline(dn->inode_folio);
+ stat_dec_inline_inode(dn->inode);
+}
+
int f2fs_convert_inline_folio(struct dnode_of_data *dn, struct folio *folio)
{
struct f2fs_io_info fio = {
@@ -157,8 +168,10 @@ int f2fs_convert_inline_folio(struct dnode_of_data *dn, struct folio *folio)
struct node_info ni;
int dirty, err;

- if (!f2fs_exist_data(dn->inode))
- goto clear_out;
+ if (!f2fs_exist_data(dn->inode)) {
+ f2fs_clear_inline_inode(dn);
+ goto out;
+ }

err = f2fs_reserve_block(dn, 0);
if (err)
@@ -206,10 +219,8 @@ int f2fs_convert_inline_folio(struct dnode_of_data *dn, struct folio *folio)

/* clear inline data and flag after data writeback */
f2fs_truncate_inline_inode(dn->inode, dn->inode_folio, 0);
- folio_clear_f2fs_inline(dn->inode_folio);
-clear_out:
- stat_dec_inline_inode(dn->inode);
- clear_inode_flag(dn->inode, FI_INLINE_DATA);
+ f2fs_clear_inline_inode(dn);
+out:
f2fs_put_dnode(dn);
return 0;
}
@@ -232,9 +243,7 @@ int f2fs_convert_inline_inode(struct inode *inode)
if (err)
return err;

- folio = f2fs_grab_cache_folio(inode->i_mapping, 0, false);
- if (IS_ERR(folio))
- return PTR_ERR(folio);
+ set_new_dnode(&dn, inode, NULL, NULL, 0);

f2fs_lock_op(sbi, &lc);

@@ -246,14 +255,23 @@ int f2fs_convert_inline_inode(struct inode *inode)

set_new_dnode(&dn, inode, ifolio, ifolio, 0);

+ if (f2fs_has_inline_data(inode) && f2fs_exist_data(inode)) {
+ folio = f2fs_grab_cache_folio(inode->i_mapping, 0, false);
+ if (IS_ERR(folio)) {
+ err = PTR_ERR(folio);
+ folio = NULL;
+ goto out;
+ }
+ }
+
if (f2fs_has_inline_data(inode))
err = f2fs_convert_inline_folio(&dn, folio);

- f2fs_put_dnode(&dn);
out:
+ f2fs_put_dnode(&dn);
f2fs_unlock_op(sbi, &lc);
-
- f2fs_folio_put(folio, true);
+ if (folio)
+ f2fs_folio_put(folio, true);

if (!err)
f2fs_balance_fs(sbi, dn.node_changed);
diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
index e7942e6e312c..e0f850b3f0c3 100644
--- a/fs/f2fs/inode.c
+++ b/fs/f2fs/inode.c
@@ -1006,13 +1006,6 @@ void f2fs_evict_inode(struct inode *inode)
}
out_clear:
fscrypt_put_encryption_info(inode);
- /*
- * Defensively truncate any remaining page cache, e.g.
- * f2fs_convert_inline_inode() called from f2fs_truncate()
- * may leave page #0 behind in the page cache when the
- * inline conversion takes the clear_out success path.
- */
- truncate_inode_pages_final(&inode->i_data);
clear_inode(inode);
}

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Subject: Re: [syzbot] [f2fs?] kernel BUG in clear_inode
Author: kth...@gmail.com

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

Corrected patch: this resend excludes the local-only inode.c hunk and tests only the upstream-applicable inline.c fix.

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Subject: Re: [syzbot] [f2fs?] kernel BUG in clear_inode
Author: kth...@gmail.com

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master