commit 367a9bffabe08c04f6d725032cce3d891b2b9e1a upstream.
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.
[konishi.ryusuke@gmail.com: adjusted for page/folio conversion] Link: https://lkml.kernel.org/r/20250107200202.6432-3-konishi.ryusuke@gmail.com Signed-off-by: Ryusuke Konishi 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: Andrew Morton akpm@linux-foundation.org --- fs/nilfs2/segment.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c index 75fd6e86f18a..2f778234ecf2 100644 --- a/fs/nilfs2/segment.c +++ b/fs/nilfs2/segment.c @@ -732,7 +732,6 @@ static size_t nilfs_lookup_dirty_data_buffers(struct inode *inode, } if (!page_has_buffers(page)) create_empty_buffers(page, i_blocksize(inode), 0); - unlock_page(page);
bh = head = page_buffers(page); do { @@ -742,11 +741,14 @@ static size_t nilfs_lookup_dirty_data_buffers(struct inode *inode, list_add_tail(&bh->b_assoc_buffers, listp); ndirties++; if (unlikely(ndirties >= nlimit)) { + unlock_page(page); pagevec_release(&pvec); cond_resched(); return ndirties; } } while (bh = bh->b_this_page, bh != head); + + unlock_page(page); } pagevec_release(&pvec); cond_resched();