From 4e8173bb52bf8b4ce5dbc67f39e960fff265b001 Mon Sep 17 00:00:00 2001 From: Ryusuke Konishi Date: Wed, 8 Jan 2025 05:00:47 +0900 Subject: [PATCH] nilfs2: protect access to buffers with no active references BugLink: https://bugs.launchpad.net/bugs/2111953 [ 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@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 Signed-off-by: Sasha Levin CVE-2025-21811 Signed-off-by: Manuel Diewald Signed-off-by: Mehmet Basaran --- 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 b6acbc262543..f392182c843a 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();