This is a note to let you know that I've just added the patch titled
nilfs2: protect access to buffers with no active references
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
nilfs2-protect-access-to-buffers-with-no-active-refe.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit b04c76616f4a18e62714594b259f42c3bcf86f85
Author: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Date: Wed Jan 8 05:00:47 2025 +0900
nilfs2: protect access to buffers with no active references
[ Upstream commit 367a9bffabe08c04f6d725032cce3d891b2b9e1a ]
nilfs_lookup_dirty_data_buffers(), which iterates through the buffers
attached to dirty data folios/pages, accesses the attached buffers without
locking the folios/pages.
For data cache, nilfs_clear_folio_dirty() may be called asynchronously
when the file system degenerates to read only, so
nilfs_lookup_dirty_data_buffers() still has the potential to cause use
after free issues when buffers lose the protection of their dirty state
midway due to this asynchronous clearing and are unintentionally freed by
try_to_free_buffers().
Eliminate this race issue by adjusting the lock section in this function.
Link: https://lkml.kernel.org/r/20250107200202.6432-3-konishi.ryusuke@xxxxxxxxx
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
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: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index 57b535921a73b..d4a98ac72b8ea 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -734,7 +734,6 @@ static size_t nilfs_lookup_dirty_data_buffers(struct inode *inode,
if (!head)
head = folio_create_empty_buffers(folio,
i_blocksize(inode), 0);
- folio_unlock(folio);
bh = head;
do {
@@ -744,11 +743,14 @@ static size_t nilfs_lookup_dirty_data_buffers(struct inode *inode,
list_add_tail(&bh->b_assoc_buffers, listp);
ndirties++;
if (unlikely(ndirties >= nlimit)) {
+ folio_unlock(folio);
folio_batch_release(&fbatch);
cond_resched();
return ndirties;
}
} while (bh = bh->b_this_page, bh != head);
+
+ folio_unlock(folio);
}
folio_batch_release(&fbatch);
cond_resched();
