From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7AB7954723; Fri, 13 Feb 2026 13:54:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770990851; cv=none; b=DBGTZxuEkXiCfiipSibLG2Pgl0QYAovJ+cbNBtfMndpiI6seghuD25qeH2JPFM+fxLMyoyXzxaY3Xbi2VlcOWfMniVNtiMbZw4yJhI7YqBg9sKOoyURfd9C2BDONhuqhi29tK0bHrursoo54Nx22WXR5Ciky2051XwBPDWlqGTg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770990851; c=relaxed/simple; bh=HPvI2NOyD9ft2wxbxYQeGVRaTYqXPC7azW7FiRcxM64=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=byKQpNLIZppsr8zqdIfYnLWYEjiDI4tWem0ZE0Uuzoz6AAASI4oFiwg3HYDroh8OJeeZjI0Jdcw5GiXGQN+L+FhRQ8iSfu4iR67OY8YRSEG5OsMyGbGaGoYvvkv3U0UjHlxKa1+aDKLdcT2/irrZTWmRFwb/YLyTbcIM+fiXE68= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=VjA93csp; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="VjA93csp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C9259C116C6; Fri, 13 Feb 2026 13:54:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1770990851; bh=HPvI2NOyD9ft2wxbxYQeGVRaTYqXPC7azW7FiRcxM64=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VjA93cspsuG95qzgZ9IqbHVfOTA8smkkHdaFgKKskFWS9Kx6OAxfBELmhtTM7EG1A G3weacMAAlmY8HL1eaK9IlGDgm29yhZgRXrKeU7opisBWkezxliLT/kdjgZn93pkJK 0hY8DVuN0KgsVJHhrxuJ17k0VpsJaLH9aZ0G9TMc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable@kernel.org, Chao Yu , Gao Xiang Subject: [PATCH 6.18 44/49] erofs: fix UAF issue for file-backed mounts w/ directio option Date: Fri, 13 Feb 2026 14:48:28 +0100 Message-ID: <20260213134710.476983411@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260213134708.885500854@linuxfoundation.org> References: <20260213134708.885500854@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chao Yu commit 1caf50ce4af096d0280d59a31abdd85703cd995c upstream. [ 9.269940][ T3222] Call trace: [ 9.269948][ T3222] ext4_file_read_iter+0xac/0x108 [ 9.269979][ T3222] vfs_iocb_iter_read+0xac/0x198 [ 9.269993][ T3222] erofs_fileio_rq_submit+0x12c/0x180 [ 9.270008][ T3222] erofs_fileio_submit_bio+0x14/0x24 [ 9.270030][ T3222] z_erofs_runqueue+0x834/0x8ac [ 9.270054][ T3222] z_erofs_read_folio+0x120/0x220 [ 9.270083][ T3222] filemap_read_folio+0x60/0x120 [ 9.270102][ T3222] filemap_fault+0xcac/0x1060 [ 9.270119][ T3222] do_pte_missing+0x2d8/0x1554 [ 9.270131][ T3222] handle_mm_fault+0x5ec/0x70c [ 9.270142][ T3222] do_page_fault+0x178/0x88c [ 9.270167][ T3222] do_translation_fault+0x38/0x54 [ 9.270183][ T3222] do_mem_abort+0x54/0xac [ 9.270208][ T3222] el0_da+0x44/0x7c [ 9.270227][ T3222] el0t_64_sync_handler+0x5c/0xf4 [ 9.270253][ T3222] el0t_64_sync+0x1bc/0x1c0 EROFS may encounter above panic when enabling file-backed mount w/ directio mount option, the root cause is it may suffer UAF in below race condition: - z_erofs_read_folio wq s_dio_done_wq - z_erofs_runqueue - erofs_fileio_submit_bio - erofs_fileio_rq_submit - vfs_iocb_iter_read - ext4_file_read_iter - ext4_dio_read_iter - iomap_dio_rw : bio was submitted and return -EIOCBQUEUED - dio_aio_complete_work - dio_complete - dio->iocb->ki_complete (erofs_fileio_ki_complete()) - kfree(rq) : it frees iocb, iocb.ki_filp can be UAF in file_accessed(). - file_accessed : access NULL file point Introduce a reference count in struct erofs_fileio_rq, and initialize it as two, both erofs_fileio_ki_complete() and erofs_fileio_rq_submit() will decrease reference count, the last one decreasing the reference count to zero will free rq. Cc: stable@kernel.org Fixes: fb176750266a ("erofs: add file-backed mount support") Fixes: 6422cde1b0d5 ("erofs: use buffered I/O for file-backed mounts by default") Signed-off-by: Chao Yu Reviewed-by: Gao Xiang Signed-off-by: Gao Xiang Signed-off-by: Greg Kroah-Hartman --- fs/erofs/fileio.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/fs/erofs/fileio.c +++ b/fs/erofs/fileio.c @@ -10,6 +10,7 @@ struct erofs_fileio_rq { struct bio bio; struct kiocb iocb; struct super_block *sb; + refcount_t ref; }; struct erofs_fileio { @@ -42,7 +43,8 @@ static void erofs_fileio_ki_complete(str } } bio_uninit(&rq->bio); - kfree(rq); + if (refcount_dec_and_test(&rq->ref)) + kfree(rq); } static void erofs_fileio_rq_submit(struct erofs_fileio_rq *rq) @@ -66,6 +68,8 @@ static void erofs_fileio_rq_submit(struc revert_creds(old_cred); if (ret != -EIOCBQUEUED) erofs_fileio_ki_complete(&rq->iocb, ret); + if (refcount_dec_and_test(&rq->ref)) + kfree(rq); } static struct erofs_fileio_rq *erofs_fileio_rq_alloc(struct erofs_map_dev *mdev) @@ -76,6 +80,7 @@ static struct erofs_fileio_rq *erofs_fil bio_init(&rq->bio, NULL, rq->bvecs, ARRAY_SIZE(rq->bvecs), REQ_OP_READ); rq->iocb.ki_filp = mdev->m_dif->file; rq->sb = mdev->m_sb; + refcount_set(&rq->ref, 2); return rq; }