From: Ryusuke Konishi Date: Tue, 7 Jan 2025 20:00:47 +0000 (+0900) Subject: nilfs2: protect access to buffers with no active references X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=367a9bffabe08c04f6d725032cce3d891b2b9e1a;p=users%2Fhch%2Fmisc.git nilfs2: protect access to buffers with no active references 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@gmail.com Signed-off-by: Ryusuke Konishi 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 --- diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c index 587251830897..58a598b548fa 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 = 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();