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=1794632206; b=JFpwUVi25GKZ9pAn1IdhflQzuRTV2EOXmrszK0pilyAob2uUvz2VEzkJT6c77RzHMAcP 6iRRXsJGkB3DXOADN1UVBkJ1lYABSf+KH0V5TsBbzI78YgAbzZrUOjIfSYhLLluQ0e/ru 8B0Lz78HZdADDZIzZaSYilgJRvXRRl5XGdkqt7er3t1wgjtitsFUnKgW6KP1kwe7bnFQQ 4YVbBxVAIRc7EqJTfXPI4l53L32RyVs7wi3uWvEnRz9jwAHv9raKHU9AdRm/c526iD7ch Vnem04z5xlzZDqIaZlBSdLRX5yhzGXdZl1H+aLSC+yfgJmRUKWBi+f20WV+2SF0GKwQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794632206; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=Fq38WdxYrlk7HWT9Rn7HOXfN4WWX6m7csVx9RyENc80=; b=Tk0DqavG2uvRLJBP2Xpvk5JXpDGZYniKVQyo9PFk0S4bcGvw9GMfa1HRzTv4vDk+NYtB xLFBn+Q1ESHIpWB/xELNyXHPWZ/p4gPyQ64ZwStcUqW68GzmqJecnpc08LPMvNKODB6Mq uwqOKp9wMMleuRIcAsyZoH1+Ub19j1IruXFBixqp5udqL76cuKd/y4jVPjxLCBy8K4eT2 fpetnMtblNr3Z7rOef3pYvAOykP8I0X1/y84B5kKNyTeQOSrApEAokYH8rwvLGzaE7J+j hvYtL1W3jhf1bKvLVZbSllU0Qm5XLcjmBZ6+3Alt5tAY5awfpJQbMxlDFDgXt3CIdRA== 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=Uc54yJYO; 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 DCCFA606A327 for ; Sat, 14 Nov 2026 04:56:46 +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=Uc54yJYO Received: by smtp.kernel.org (Postfix) with ESMTPSA id B3BF81F000C4; Sat, 14 Nov 2026 04:56:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794632206; bh=Fq38WdxYrlk7HWT9Rn7HOXfN4WWX6m7csVx9RyENc80=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Uc54yJYO7GG0gTyY90CetBycirTCfAcGt7ZAMKCQevqq7bkoYcXnNzQ1EnCFUZet6 RyI+OU50Kf2FUFobc4RrhQEA7rjFkqtSKbxbHdBeDNDYoipY1x+7XrhUibfs0HVIG7 qJIwRrgEjUPO2wrM4hMQ/f6jXvHSHgBUCB4yyaFctfkWEzLZbjLIX9IScCRSfC4C0A E7VM4fQhPAGfZ5OHGxIA2UXQXwelAUVJCCzy77Ok+8CIPL4QhRhYobCGGaJYrDMC1h Mo4RFfLmHo+61hTTh9C2K5ngFbtP1Lj85zm//9Sm9u1jVigsftDg+9XwWDlNs+gOVT /qrmPV2/oq40Q== 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 5.15.y] mm/filemap: read mapping->a_ops->free_folio under i_lock Date: Fri, 13 Nov 2026 23:56:44 -0500 Message-ID: <20261114045632.2986009-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261109202107-failed-5.15-dc24e273244e@kernel.org> References: <20261109202107-failed-5.15-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: Adapted callback capture from free_folio under i_lock to freepage under i_pages. ] Signed-off-by: Sasha Levin --- mm/filemap.c | 44 ++++++++++++++++++++++++-------------------- 1 file changed, 24 insertions(+), 20 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index 9fec53a3f5505..eccc5318b6644 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -232,23 +232,6 @@ void __delete_from_page_cache(struct page *page, void *shadow) page_cache_delete(mapping, page, shadow); } -static void page_cache_free_page(struct address_space *mapping, - struct page *page) -{ - void (*freepage)(struct page *); - - freepage = mapping->a_ops->freepage; - if (freepage) - freepage(page); - - if (PageTransHuge(page) && !PageHuge(page)) { - page_ref_sub(page, thp_nr_pages(page)); - VM_BUG_ON_PAGE(page_count(page) <= 0, page); - } else { - put_page(page); - } -} - /** * delete_from_page_cache - delete page from page cache * @page: the page which the kernel is trying to remove from page cache @@ -260,13 +243,22 @@ static void page_cache_free_page(struct address_space *mapping, void delete_from_page_cache(struct page *page) { struct address_space *mapping = page_mapping(page); + void (*freepage)(struct page *page); BUG_ON(!PageLocked(page)); xa_lock_irq(&mapping->i_pages); __delete_from_page_cache(page, NULL); + freepage = mapping->a_ops->freepage; xa_unlock_irq(&mapping->i_pages); - page_cache_free_page(mapping, page); + if (freepage) + freepage(page); + if (PageTransHuge(page) && !PageHuge(page)) { + page_ref_sub(page, thp_nr_pages(page)); + VM_BUG_ON_PAGE(page_count(page) <= 0, page); + } else { + put_page(page); + } } EXPORT_SYMBOL(delete_from_page_cache); @@ -335,6 +327,7 @@ static void page_cache_delete_batch(struct address_space *mapping, void delete_from_page_cache_batch(struct address_space *mapping, struct pagevec *pvec) { + void (*freepage)(struct page *page); int i; if (!pagevec_count(pvec)) @@ -347,10 +340,21 @@ void delete_from_page_cache_batch(struct address_space *mapping, unaccount_page_cache_page(mapping, pvec->pages[i]); } page_cache_delete_batch(mapping, pvec); + freepage = mapping->a_ops->freepage; xa_unlock_irq(&mapping->i_pages); - for (i = 0; i < pagevec_count(pvec); i++) - page_cache_free_page(mapping, pvec->pages[i]); + for (i = 0; i < pagevec_count(pvec); i++) { + struct page *page = pvec->pages[i]; + + if (freepage) + freepage(page); + if (PageTransHuge(page) && !PageHuge(page)) { + page_ref_sub(page, thp_nr_pages(page)); + VM_BUG_ON_PAGE(page_count(page) <= 0, page); + } else { + put_page(page); + } + } } int filemap_check_errors(struct address_space *mapping) -- 2.53.0