[PATCH RFC] udf: Mark LVID buffer as uptodate before marking it dirty in open/sync

[syzbot]

When an I/O error occurs while writing the Logical Volume Integrity
Descriptor (LVID) buffer to the block device, the block layer's completion
handler (`end_buffer_write_sync()`) clears the `BH_Uptodate` flag on the
buffer. However, the buffer still contains valid LVID data in memory. If
the filesystem is subsequently remounted read-write or synced,
`udf_open_lvid()` or `udf_sync_fs()` will modify the LVID buffer and call
`mark_buffer_dirty()`. This triggers a spurious
`WARN_ON_ONCE(!buffer_uptodate(bh))` warning in `mark_buffer_dirty()`
because the buffer is not marked uptodate, even though its in-memory
contents are valid and are about to be overwritten.

To prevent this spurious warning, unconditionally set the `BH_Uptodate`
flag before calling `mark_buffer_dirty()` in `udf_open_lvid()` and
`udf_sync_fs()`. This acknowledges that the in-memory buffer is valid and
matches the workaround previously applied to `udf_close_lvid()` in commit
853a0c25baf9 ("udf: Mark LVID buffer as uptodate before marking it dirty").
Extending this workaround ensures consistent behavior across all LVID
updates.

Buffer I/O error on dev loop0, logical block 128, lost sync page write
------------[ cut here ]------------
!buffer_uptodate(bh)
WARNING: fs/buffer.c:1087 at mark_buffer_dirty+0x299/0x410 fs/buffer.c:1087
...
Call Trace:
<TASK>
udf_open_lvid+0x369/0x5b0 fs/udf/super.c:2078
udf_reconfigure+0x336/0x540 fs/udf/super.c:679
reconfigure_super+0x232/0x8f0 fs/super.c:1080
vfs_cmd_reconfigure fs/fsopen.c:268 [inline]
vfs_fsconfig_locked+0x171/0x320 fs/fsopen.c:297
__do_sys_fsconfig fs/fsopen.c:463 [inline]
__se_sys_fsconfig+0x6b9/0x810 fs/fsopen.c:350
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
</TASK>

Fixes: 853a0c25baf9 ("udf: Mark LVID buffer as uptodate before marking it dirty")
Assisted-by: Gemini:gemini-3.1-pro-preview Gemini:gemini-3-flash-preview syzbot
Reported-by: syzbot+0306b3...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=0306b38d9ed6ef71467d
Link: https://syzkaller.appspot.com/ai_job?id=83a8a238-e94a-44e6-8088-8640cf9cb7e0
To: "Jan Kara" <ja...@suse.com>
To: <linux-...@vger.kernel.org>

---
diff --git a/fs/udf/super.c b/fs/udf/super.c
index cad2e15d6..7a5e9bd11 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -2075,6 +2075,12 @@ static void udf_open_lvid(struct super_block *sb)
UDF_SET_FLAG(sb, UDF_FLAG_INCONSISTENT);

udf_finalize_lvid(lvid);
+ /*
+ * We set buffer uptodate unconditionally here to avoid spurious
+ * warnings from mark_buffer_dirty() when previous EIO has marked
+ * the buffer as !uptodate
+ */
+ set_buffer_uptodate(bh);
mark_buffer_dirty(bh);
sbi->s_lvid_dirty = 0;
mutex_unlock(&sbi->s_alloc_mutex);
@@ -2397,6 +2403,12 @@ static int udf_sync_fs(struct super_block *sb, int wait)
* Blockdevice will be synced later so we don't have to submit
* the buffer for IO
*/
+ /*
+ * We set buffer uptodate unconditionally here to avoid spurious
+ * warnings from mark_buffer_dirty() when previous EIO has marked
+ * the buffer as !uptodate
+ */
+ set_buffer_uptodate(bh);
mark_buffer_dirty(bh);
sbi->s_lvid_dirty = 0;
}


base-commit: 8cd9520d35a6c38db6567e97dd93b1f11f185dc6
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[Aleksandr Nogikh]

On Mon, Jun 22, 2026 at 7:43 PM 'syzbot' via
syzkaller-upstream-moderation

Now there are three places in the super.c file that do the same and
have the same comment. Maybe extrat it to some function and call it
from the 3 places?

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