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=1794630127; b=T+DV3uewzGiLocM3DcqgSaqP8RVEcGJIZZtyYpZyJTfFiF3t/MPooykYQyytjpwnGoDF K32AULMZcJpvdHyxrY21ZbN5SxU10MTFSUp6Df/DdwoTP3muOg8BeXC1aKXJEOdE81tie x4FRJk6E169GyDc1YiJvegP2B5oJIQTHCaDGaQRG2rCIdKmruHFx1tvtrSLwszlWFkssc PgkIlRgplnBAw6Ws0AfES7BcAuFnrSLxFVwbRm5dJGUGYqM6V4tnHQJ7qbk48xc8FUHpP 24vhRSokTz2q4yPXJidECXiiIW2agpjVpdsPCMKOVadXLb8mglN4Nw46ScugTYSZykg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794630127; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=GUeVhR0JjXcyFFVYBAIi5lG7lbTkoAV/YstHNFy6jvc=; b=wkLvgb7c054onn+EZyygd5u5ympTMjtkzM4bef/COXSROfELuj7px8ZuYDtPzUD2iKyl OU4k4BOenzRY1wg8N13D8xm7zg0/TxK1YsDCr5pb2r2jaLrZgImhgs2Cyq7CU2WbB7+yc XKT2YQudteOvrUkgQcbDiOOM3K6at9IUt/uwGha7QFKGofpD5JYZQrxV+qmV7L6BGeyIZ mSvqWb1gCyPM1zQYn03+qkeljbADmyT/ukEtSH/njH7OdhtjNcbDHynnCJfCrQQN9YbCY TPsl5DLEFRzhCwThSJSgGLwMN3F5yLxDlgjRp1uAv4+heiwZr2oliBB6Gu3QZalCYvQ== 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=ehs+3lyW; 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 03E99606A323 for ; Sat, 14 Nov 2026 04:22:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=ehs+3lyW Received: by smtp.kernel.org (Postfix) with ESMTPSA id A17111F000C4; Sat, 14 Nov 2026 04:22:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794630126; bh=GUeVhR0JjXcyFFVYBAIi5lG7lbTkoAV/YstHNFy6jvc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ehs+3lyW39Dal/7mwPtmQ3xjl/MIdaVd9gKfLCmKTSACGXrXLgYedI8lqAouMWGT3 W6y8QOYB7KD/+zXnXI6OF6dyvScOmFziN5nZ/pRRrt6OG45bm3FMBK5JcI8QHwyJTt TduxB1REWuoZzDpYI3HmXP88x8Ehrvx8JUlFLLeamlnbjnecyUoAs98qDqzFZP5wH1 ykG+vd5o170vcdsnLm+7egxw02xQbrVNLmHPY3VDNo6HQMV2ELiEO3rtTyLgohFz6A Q7aiRs0umrKe+JT2D0Mqvx9VXJHi9xOEKr3csTgFrdPWykFvBWFrM/RzUVJcrR4Q/B 1r0QaofCid3Xg== From: Sasha Levin To: stable@vger.kernel.org Cc: Josef Bacik , Rik van Riel , Muhammad Usama Anjum , Zi Yan , "David Hildenbrand (Arm)" , Sasha Levin Subject: [PATCH 6.18.y] mm/filemap: read mapping->a_ops->free_folio under i_lock Date: Fri, 13 Nov 2026 23:22:04 -0500 Message-ID: <20261114042149.2838075-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261109200315-failed-6.18-dc24e273244e@kernel.org> References: <20261109200315-failed-6.18-dc24e273244e@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Josef Bacik [ Upstream commit dc24e273244e9d712257d5a6c20a32c7f5ca84e6 ] 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 Tested-by: Muhammad Usama Anjum Reviewed-by: Zi Yan Link: https://patch.msgid.link/20261031-fixes_core-v3-6-d6437171ecc3@kernel.org Signed-off-by: David Hildenbrand (Arm) [ sashal: Adjusted patch context to retain inode_add_lru() instead of inode_lru_list_add(). ] Signed-off-by: Sasha Levin --- mm/filemap.c | 29 ++++++++++++++--------------- 1 file changed, 14 insertions(+), 15 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index cd7af384cff26..ee6594e691456 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_add_lru(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_add_lru(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) -- 2.53.0