nilfs2: fix kernel bug due to missing clearing of buffer delay flag

commit 6ed469df0bfbef3e4b44fca954a781919db9f7ab upstream.

Syzbot reported that after nilfs2 reads a corrupted file system image
and degrades to read-only, the BUG_ON check for the buffer delay flag
in submit_bh_wbc() may fail, causing a kernel bug.

This is because the buffer delay flag is not cleared when clearing the
buffer state flags to discard a page/folio or a buffer head. So, fix
this.

This became necessary when the use of nilfs2's own page clear routine
was expanded.  This state inconsistency does not occur if the buffer
is written normally by log writing.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Link: https://lore.kernel.org/r/20241015213300.7114-1-konishi.ryusuke@gmail.com
Fixes: 8c26c4e2694a ("nilfs2: fix issue with flush kernel thread after remount in RO mode because of driver's internal error or metadata corruption")
Reported-by: syzbot+985ada84bf055a575c07@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=985ada84bf055a575c07
Cc: stable@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/nilfs2/page.c b/fs/nilfs2/page.c
index 81992b9a219b212fb41893d99cdca7895688543c..98be72e93b401b7d5c34ace88a78874acfbfe490 100644 (file)
--- a/fs/nilfs2/page.c
+++ b/fs/nilfs2/page.c
@@ -77,7 +77,8 @@ void nilfs_forget_buffer(struct buffer_head *bh)
        const unsigned long clear_bits =
                (BIT(BH_Uptodate) | BIT(BH_Dirty) | BIT(BH_Mapped) |
                 BIT(BH_Async_Write) | BIT(BH_NILFS_Volatile) |
-                BIT(BH_NILFS_Checked) | BIT(BH_NILFS_Redirected));
+                BIT(BH_NILFS_Checked) | BIT(BH_NILFS_Redirected) |
+                BIT(BH_Delay));
 
        lock_buffer(bh);
        set_mask_bits(&bh->b_state, clear_bits, 0);
@@ -409,7 +410,8 @@ void nilfs_clear_dirty_page(struct page *page, bool silent)
                const unsigned long clear_bits =
                        (BIT(BH_Uptodate) | BIT(BH_Dirty) | BIT(BH_Mapped) |
                         BIT(BH_Async_Write) | BIT(BH_NILFS_Volatile) |
-                        BIT(BH_NILFS_Checked) | BIT(BH_NILFS_Redirected));
+                        BIT(BH_NILFS_Checked) | BIT(BH_NILFS_Redirected) |
+                        BIT(BH_Delay));
 
                bh = head = page_buffers(page);
                do {