From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793306099; b=Hxdw34NjeanG9jZvU51lnAAtmIlDGkIgdu+QduNZNetUC26vAhK5UCIecd7Gg/Y/qr3F POHc9n9fz1Q7zxB6WoJUmLvhX687GsBW+TvCV4dlPdkepUij9Xqfw147N5ruTKdIBon5Z us7G8GuTK4Md36inOj8XEjjeYRHUWDBIxiq66yq9E5axhBGe9tFm0ZNBJJ7b84Q6KFo0h +R2opptWiOp+qktm95AWD50h34YYklE1GX4THPqOUIRNSJRhMhSpwYNaJ1COy1Wu9G4Dg yh9ZWITwWWn2zRZMgNmcYtLlJe/QtO+Tc+UmG0b4cPvmO2BfwEucqtYkKcwY50nqrwQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793306099; h=Received:DKIM-Signature:From:Date:Subject:MIME-Version:Content-Type: Content-Transfer-Encoding:Message-Id:References:In-Reply-To:To:Cc: X-Mailer:X-Developer-Signature:X-Developer-Key; bh=KxYr7Sm6OEegxhd0iVI9DwNJDZ8ymD/S/fyvDRwEbZs=; b=poJOfbxtBP7looHvNDjn7V1n62S3Z0LgjVp8LorPxB+J/WsMczIdSIXjDkKJK7+/WP23 hEVo+ySYdIwHGaZuTcCm5woOugZ+DdP7NxMcnPPiq1uq217kC4YhkW1+VBxIPfoj1PFZD Mf2eTi97xtkFmJ56c3mxY/Gtgm4GXUj5nx/a9BZ6jSUeFENBsZtejzZfCrNJ5X5oEbi14 lIjwZX71u/jLIIOxk3XsrEU/KCpkk0JOjuk3sq2s9rhSTu0mCFOtz7Tkxn5YDpyVyGSKQ KoJywobPwsW09XZ+0J6XYGr3r2l8DkdzxCpRm8zj5YzgCJkLsZ9SsBhz8meaqoGiiSQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=m8stvVUt; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1040F606A32A; Thu, 29 Oct 2026 20:34:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=m8stvVUt Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3413D1F01826; Thu, 29 Oct 2026 20:34:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793306098; bh=KxYr7Sm6OEegxhd0iVI9DwNJDZ8ymD/S/fyvDRwEbZs=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=m8stvVUtaQ1zzXBZo9b4DXWtjQAwfK94PwzaJ/eyWlctn2jfEk/kIccDZT4yzRzTV xUwhkYp4JFgiEQbnWZ93UJ8mt2S+Web/7pzGe0SpkYI6oocQZiPLpHT73hP74roi3D Yr+BUk3pE/quR4/Ig1StPmT2uOE6hcTPcUKEVJ/Lv5UMx5k4G06IaFelmWSX8rEvzA ylUcnc1dGEcjLRHd7oeEGKeFW/1BtT4p1adLyRlFCZ+tJKXJz8Wd3CUiSLA5LptqrQ Lopmi7EvwC7Ts8BZAb+MLwTj6XScPpqfDLchayfM4KgiBF4iArRR7JwJRL9P4FDqwX OjQa5upyhqaBA== From: "David Hildenbrand (Arm)" Date: Thu, 29 Oct 2026 21:33:01 +0100 Subject: [PATCH v2 06/47] mm/filemap: read mapping->a_ops->free_folio under i_lock X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261029-fixes_core-v2-6-a64ce7f83abb@kernel.org> References: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> In-Reply-To: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> To: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Pedro Falcato , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Dev Jain , Usama Arif , Kiryl Shutsemau , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, Josef Bacik , stable@vger.kernel.org, "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3722; i=david@kernel.org; h=from:subject:message-id; bh=QdrOe18hQtm70tC+kr29IxB4g7ljmyzLHze5efGpjA8=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLIer22pSz/Yr2rC1Wyzv75dSO/9zxyjvv59K06tKJoq7 jFNwXtbRykLgxgHg6yYIktQ8H2Dly/X1Va78THDzGFlAhnCwMUpABOpqmNkOBziF+Ztzcv74uOs M8/99SO2irj9uWaeLBJ/3eKDe2PYO0aG15ob3G0e/LRW1gmRjJv2v3bv/R1bGjMeL888u3fdBef zDAA= X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A From: Josef Bacik memory_failure() -> ... -> filemap_remove_folio() can read mapping->a_ops after the inode has been freed. Once the folio is deleted from the pagecache it no longer pins the mapping, so after i_lock is dropped e.g., a concurrent final iput() can evict and free the inode before filemap_free_folio() looks up mapping->a_ops->free_folio. Most callers hold a reference on the inode, but not all. Documentation/filesystems/vfs.rst explicitly states that ->free_folio() must not assume the original address_space mapping still exists. Fix it by loading ->free_folio while i_lock is still held, similar to what folio_unmap_invalidate() does. Inline filemap_free_folio() into its remaining caller such that delete_from_page_cache_batch() also just loads the callback before dropping the i_lock. The bug was found by code inspection and has not been reproduced. Fix generated by an LLM and sent by Josef Bacik in private. Fixes: 59c66c5f8c4f ("mm: factor out page cache page freeing into a separate function") Cc: stable@vger.kernel.org Signed-off-by: Josef Bacik [ david: get rid of filemap_free_folio() entirely; improve patch description ] Reviewed-by: Rik van Riel Signed-off-by: David Hildenbrand (Arm) --- mm/filemap.c | 29 ++++++++++++++--------------- 1 file changed, 14 insertions(+), 15 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index b74bc1e5015c..906b013c11eb 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -227,18 +227,6 @@ void __filemap_remove_folio(struct folio *folio, void *shadow) page_cache_delete(mapping, folio, shadow); } -static void filemap_free_folio(const struct address_space *mapping, - struct folio *folio) -{ - void (*free_folio)(struct folio *); - - free_folio = mapping->a_ops->free_folio; - if (free_folio) - free_folio(folio); - - folio_put_refs(folio, folio_nr_pages(folio)); -} - /** * filemap_remove_folio - Remove folio from page cache. * @folio: The folio. @@ -250,6 +238,7 @@ static void filemap_free_folio(const struct address_space *mapping, void filemap_remove_folio(struct folio *folio) { struct address_space *mapping = folio->mapping; + void (*free_folio)(struct folio *folio); BUG_ON(!folio_test_locked(folio)); spin_lock(&mapping->host->i_lock); @@ -258,9 +247,12 @@ void filemap_remove_folio(struct folio *folio) xa_unlock_irq(&mapping->i_pages); if (mapping_shrinkable(mapping)) inode_lru_list_add(mapping->host); + free_folio = mapping->a_ops->free_folio; spin_unlock(&mapping->host->i_lock); - filemap_free_folio(mapping, folio); + if (free_folio) + free_folio(folio); + folio_put_refs(folio, folio_nr_pages(folio)); } /* @@ -320,6 +312,7 @@ static void page_cache_delete_batch(struct address_space *mapping, void delete_from_page_cache_batch(struct address_space *mapping, struct folio_batch *fbatch) { + void (*free_folio)(struct folio *folio); int i; if (!folio_batch_count(fbatch)) @@ -337,10 +330,16 @@ void delete_from_page_cache_batch(struct address_space *mapping, xa_unlock_irq(&mapping->i_pages); if (mapping_shrinkable(mapping)) inode_lru_list_add(mapping->host); + free_folio = mapping->a_ops->free_folio; spin_unlock(&mapping->host->i_lock); - for (i = 0; i < folio_batch_count(fbatch); i++) - filemap_free_folio(mapping, fbatch->folios[i]); + for (i = 0; i < folio_batch_count(fbatch); i++) { + struct folio *folio = fbatch->folios[i]; + + if (free_folio) + free_folio(folio); + folio_put_refs(folio, folio_nr_pages(folio)); + } } int filemap_check_errors(struct address_space *mapping) -- 2.43.0