[PATCH 4.19 5.4 5.10 5.15 6.1 6.6] nilfs2: fix kernel bug due to missing clearing of checked flag

[Ryusuke Konishi <konishi.ryusuke@gmail.com>]

commit 41e192ad2779cae0102879612dfe46726e4396aa upstream.

Syzbot reported that in directory operations after nilfs2 detects
filesystem corruption and degrades to read-only,
__block_write_begin_int(), which is called to prepare block writes, may
fail the BUG_ON check for accesses exceeding the folio/page size,
triggering a kernel bug.

This was found to be because the "checked" flag of a page/folio was not
cleared when it was discarded by nilfs2's own routine, which causes the
sanity check of directory entries to be skipped when the directory
page/folio is reloaded.  So, fix that.

This was necessary when the use of nilfs2's own page discard routine was
applied to more than just metadata files.

Link: https://lkml.kernel.org/r/20241017193359.5051-1-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")
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Reported-by: syzbot+d6ca2daf692c7a82f959@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=d6ca2daf692c7a82f959
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
Please apply this patch to the stable trees indicated by the subject
prefix instead of the failed patches.

This patch is tailored to take page/folio conversion into account.
Compiled and tested successfully.

Thanks,
Ryusuke Konishi

 fs/nilfs2/page.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/nilfs2/page.c b/fs/nilfs2/page.c
index 36d29c183bb7..956c90700e15 100644
--- a/fs/nilfs2/page.c
+++ b/fs/nilfs2/page.c
@@ -405,6 +405,7 @@ void nilfs_clear_dirty_page(struct page *page, bool silent)
 
 	ClearPageUptodate(page);
 	ClearPageMappedToDisk(page);
+	ClearPageChecked(page);
 
 	if (page_has_buffers(page)) {
 		struct buffer_head *bh, *head;
-- 
2.43.5