[syzbot] [ext4?] kernel BUG in ext4_write_inline_data (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 162b42445b58 Merge tag 'iommu-fixes-v6.19-rc7' of git://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12c48402580000
kernel config: https://syzkaller.appspot.com/x/.config?x=fea461e951c03b1b
dashboard link: https://syzkaller.appspot.com/bug?extid=7de5fe447862fc37576f
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11ec7bfa580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/98939f243052/disk-162b4244.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2ce9a7b8e049/vmlinux-162b4244.xz
kernel image: https://storage.googleapis.com/syzbot-assets/99eb2d7c3e94/bzImage-162b4244.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/82c4262402e2/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=1196145a580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7de5fe...@syzkaller.appspotmail.com

------------[ cut here ]------------
kernel BUG at fs/ext4/inline.c:240!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 6836 Comm: syz.5.137 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
RIP: 0010:ext4_write_inline_data+0x40b/0x4f0 fs/ext4/inline.c:240
Code: fe e8 e9 70 3f ff 42 8d 44 23 c4 bb 3c 00 00 00 89 44 24 08 44 29 e3 e9 aa fe ff ff e8 ce 70 3f ff 90 0f 0b e8 c6 70 3f ff 90 <0f> 0b e8 be 70 3f ff 48 8d 3d b7 58 f6 0d 48 c7 c2 60 5b ac 8b 4c
RSP: 0018:ffffc9000b0b74e0 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000001000 RCX: ffffffff82c7675b
RDX: ffff88802c845b80 RSI: ffffffff82c7697a RDI: ffff88802c845b80
RBP: ffff888075742918 R08: 0000000000000006 R09: 0000000000004000
R10: 000000000000003c R11: 0000000000000000 R12: 0000000000003000
R13: 0000000000004000 R14: ffffc9000b0b7580 R15: ffff888075742e82
FS: 00007fb1c0b036c0(0000) GS:ffff8881245dc000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f284e6ff000 CR3: 000000005cb37000 CR4: 0000000000350ef0
Call Trace:
<TASK>
ext4_write_inline_data_end+0x2a8/0xdb0 fs/ext4/inline.c:817
ext4_da_write_end+0x4f7/0xf20 fs/ext4/inode.c:3286
generic_perform_write+0x513/0xa40 mm/filemap.c:4335
ext4_buffered_write_iter+0x119/0x440 fs/ext4/file.c:299
ext4_file_write_iter+0xa3d/0x1d90 fs/ext4/file.c:723
iter_file_splice_write+0x82b/0x10a0 fs/splice.c:738
do_splice_from fs/splice.c:938 [inline]
direct_splice_actor+0x192/0x6c0 fs/splice.c:1161
splice_direct_to_actor+0x345/0xa30 fs/splice.c:1105
do_splice_direct_actor fs/splice.c:1204 [inline]
do_splice_direct+0x174/0x240 fs/splice.c:1230
do_sendfile+0xadc/0xe20 fs/read_write.c:1370
__do_sys_sendfile64 fs/read_write.c:1431 [inline]
__se_sys_sendfile64 fs/read_write.c:1417 [inline]
__x64_sys_sendfile64+0x1d8/0x220 fs/read_write.c:1417
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xc9/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb1bfb9aeb9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fb1c0b03028 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007fb1bfe15fa0 RCX: 00007fb1bfb9aeb9
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000004
RBP: 00007fb1bfc08c1f R08: 0000000000000000 R09: 0000000000000000
R10: 000000000e3aa6ea R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb1bfe16038 R14: 00007fb1bfe15fa0 R15: 00007ffc03931cf8
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:ext4_write_inline_data+0x40b/0x4f0 fs/ext4/inline.c:240
Code: fe e8 e9 70 3f ff 42 8d 44 23 c4 bb 3c 00 00 00 89 44 24 08 44 29 e3 e9 aa fe ff ff e8 ce 70 3f ff 90 0f 0b e8 c6 70 3f ff 90 <0f> 0b e8 be 70 3f ff 48 8d 3d b7 58 f6 0d 48 c7 c2 60 5b ac 8b 4c
RSP: 0018:ffffc9000b0b74e0 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000001000 RCX: ffffffff82c7675b
RDX: ffff88802c845b80 RSI: ffffffff82c7697a RDI: ffff88802c845b80
RBP: ffff888075742918 R08: 0000000000000006 R09: 0000000000004000
R10: 000000000000003c R11: 0000000000000000 R12: 0000000000003000
R13: 0000000000004000 R14: ffffc9000b0b7580 R15: ffff888075742e82
FS: 00007fb1c0b036c0(0000) GS:ffff8881246dc000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007efdf1812000 CR3: 000000005cb37000 CR4: 0000000000350ef0


---
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***

Subject: [PATCH] ext4: add debug logging for inline data flag in ext4_iget
Author: karti...@gmail.com

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


Add debug printk statements to track inline data flag status and inode
size during inode loading. This helps diagnose corruption issues where
the EXT4_INLINE_DATA_FL flag may be set inconsistently with the actual
inode size.

The debug output logs:
- Raw inode mode, flags, and size fields
- Whether INLINE_DATA flag is set
- Whether EXTENTS flag is set

This is useful for investigating crashes in ext4_write_inline_data()
where the BUG_ON(pos + len > EXT4_I(inode)->i_inline_size) triggers
due to corrupted filesystem images that have inline data flag set
but file size exceeding inline capacity.

Reported-by: syzbot+7de5fe...@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=7de5fe447862fc37576f
Signed-off-by: Deepanshu Kartikey <Karti...@gmail.com>
---
fs/ext4/inode.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 0c466ccbed69..ad6eff690edd 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5211,6 +5211,22 @@ struct inode *__ext4_iget(struct super_block *sb, unsigned long ino,
goto bad_inode;
raw_inode = ext4_raw_inode(&iloc);

+ printk(KERN_WARNING "EXT4-fs DEBUG: inode=%lu i_mode=0x%x i_flags=0x%x i_size_lo=%u i_size_hi=%u\n",
+ ino,
+ le16_to_cpu(raw_inode->i_mode),
+ le32_to_cpu(raw_inode->i_flags),
+ le32_to_cpu(raw_inode->i_size_lo),
+ le32_to_cpu(raw_inode->i_size_high));
+ /* Check if inline flag is set in raw flags */
+ if (le32_to_cpu(raw_inode->i_flags) & EXT4_INLINE_DATA_FL) {
+ printk(KERN_WARNING "EXT4-fs DEBUG: inode=%lu has INLINE_DATA flag set!\n", ino);
+ }
+
+ /* Check if extents flag is set in raw flags */
+ if (le32_to_cpu(raw_inode->i_flags) & EXT4_EXTENTS_FL) {
+ printk(KERN_WARNING "EXT4-fs DEBUG: inode=%lu has EXTENTS flag set!\n", ino);
+ }
+
if ((flags & EXT4_IGET_HANDLE) &&
(raw_inode->i_links_count == 0) && (raw_inode->i_mode == 0)) {
ret = -ESTALE;
--
2.43.0