On Thu, Aug 28, 2025 at 1:16 PM Max Kellermann max.kellermann@ionos.com wrote:

The function move_dirty_folio_in_page_array() was created by commit ce80b76dd327 ("ceph: introduce ceph_process_folio_batch() method") by moving code from ceph_writepages_start() to this function.

This new function is supposed to return an error code which is checked by the caller (now ceph_process_folio_batch()), and on error, the caller invokes redirty_page_for_writepage() and then breaks from the loop.

However, the refactoring commit has gone wrong, and it by accident, it always returns 0 (= success) because it first NULLs the pointer and then returns PTR_ERR(NULL) which is always 0. This means errors are silently ignored, leaving NULL entries in the page array, which may later crash the kernel.

The simple solution is to call PTR_ERR() before clearing the pointer.

Fixes: ce80b76dd327 ("ceph: introduce ceph_process_folio_batch() method") Link: https://lore.kernel.org/ceph-devel/aK4v548CId5GIKG1@swift.blarg.de/ Cc: stable@vger.kernel.org Signed-off-by: Max Kellermann max.kellermann@ionos.com

---

fs/ceph/addr.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c index 8b202d789e93..e3e0d477f3f7 100644 --- a/fs/ceph/addr.c +++ b/fs/ceph/addr.c @@ -1264,7 +1264,9 @@ static inline int move_dirty_folio_in_page_array(struct address_space *mapping, 0, gfp_flags); if (IS_ERR(pages[index])) {

•                   if (PTR_ERR(pages[index]) == -EINVAL) {
  

•                   int err = PTR_ERR(pages[index]);
  

•                   if (err == -EINVAL) {
                            pr_err_client(cl, "inode->i_blkbits=%hhu\n",
                                            inode->i_blkbits);
                    }
  

@@ -1273,7 +1275,7 @@ static inline int move_dirty_folio_in_page_array(struct address_space *mapping, BUG_ON(ceph_wbc->locked_pages == 0);

                    pages[index] = NULL;

•                   return PTR_ERR(pages[index]);
  

•                   return err;
            }
    } else {
            pages[index] = &folio->page;
  

-- 2.47.2

Queued up for 6.17-rc6.

Thanks,

Ilya