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| author | Deepakkumar Karn <dkarn@redhat.com> | 2025-12-11 16:12:11 +0300 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2025-12-15 17:07:22 +0300 |
| commit | b68f91ef3b3fe82ad78c417de71b675699a8467c (patch) | |
| tree | 53b7ff46b8c071dd662c3c8c939ef9c7df7ca349 | |
| parent | 961b2ad1b4131c947cbc75700c83a6deb0c91d02 (diff) | |
| download | linux-b68f91ef3b3fe82ad78c417de71b675699a8467c.tar.xz | |
fs/buffer: add alert in try_to_free_buffers() for folios without buffers
try_to_free_buffers() can be called on folios with no buffers attached
when filemap_release_folio() is invoked on a folio belonging to a mapping
with AS_RELEASE_ALWAYS set but no release_folio operation defined.
In such cases, folio_needs_release() returns true because of the
AS_RELEASE_ALWAYS flag, but the folio has no private buffer data. This
causes try_to_free_buffers() to call drop_buffers() on a folio with no
buffers, leading to a null pointer dereference.
Adding a check in try_to_free_buffers() to return early if the folio has no
buffers attached, with WARN_ON_ONCE() to alert about the misconfiguration.
This provides defensive hardening.
Signed-off-by: Deepakkumar Karn <dkarn@redhat.com>
Link: https://patch.msgid.link/20251211131211.308021-1-dkarn@redhat.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
| -rw-r--r-- | fs/buffer.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/fs/buffer.c b/fs/buffer.c index c6f4660f92df..fd53b806ab7e 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -2948,6 +2948,10 @@ bool try_to_free_buffers(struct folio *folio) if (folio_test_writeback(folio)) return false; + /* Misconfigured folio check */ + if (WARN_ON_ONCE(!folio_buffers(folio))) + return true; + if (mapping == NULL) { /* can this still happen? */ ret = drop_buffers(folio, &buffers_to_free); goto out; |