From patchwork Fri Jul 14 14:42:25 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Darrick J. Wong" X-Patchwork-Id: 13313751 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A0C8FC0015E for ; Fri, 14 Jul 2023 14:42:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235576AbjGNOmc (ORCPT ); Fri, 14 Jul 2023 10:42:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53738 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236130AbjGNOm3 (ORCPT ); Fri, 14 Jul 2023 10:42:29 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F25122D51 for ; Fri, 14 Jul 2023 07:42:26 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 54DE761D39 for ; Fri, 14 Jul 2023 14:42:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AF22EC433C7; Fri, 14 Jul 2023 14:42:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1689345745; bh=b5iBdfpDEdAu9oltYPk59gVWK75Ycq+h3tHmVyKaLRA=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=FA5aj6P9Ke7hjz3WWmGHwkDUDcFkh0E0DYKvujYsrvFtQIIXPvfdUVqgnQ2qHAXqK MrUG9SDJxwJbpe2c6OB/IhzjkvpKjpQYVidRI90/tVRyzC+7qLQo9dmRCKcAnnAK4z TktrD2bLmP+CzF4b2wWXJ9SNsLK1Er+UYUbRkq/xy1heM7BpEQvnyPSWCIa0QZDaWb 8ltWkkr21Yt2XeEX5rPtdSzsdF84u2Puo2DOYcMwKoCoZ/dpvqD3F7rbNW4iAAj8a6 eYDEnHs7RpTaebGR5GBebXMloowOYzHGRhZVJPdocojGrPHBG+JdrRiayqhL7o7jxu 72ZMv2fPeE5vw== Subject: [PATCH 1/3] xfs: convert flex-array declarations in struct xfs_attrlist* From: "Darrick J. Wong" To: david@fromorbit.com, djwong@kernel.org Cc: linux-xfs@vger.kernel.org, keescook@chromium.org Date: Fri, 14 Jul 2023 07:42:25 -0700 Message-ID: <168934574525.3353217.6410696992399754759.stgit@frogsfrogsfrogs> In-Reply-To: <168934573961.3353217.18139786322840965874.stgit@frogsfrogsfrogs> References: <168934573961.3353217.18139786322840965874.stgit@frogsfrogsfrogs> User-Agent: StGit/0.19 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org From: Darrick J. Wong As of 6.5-rc1, UBSAN trips over the attrlist ioctl definitions using an array length of 1 to pretend to be a flex array. Kernel compilers have to support unbounded array declarations, so let's correct this. This may cause friction with userspace header declarations, but suck is life. ================================================================================ UBSAN: array-index-out-of-bounds in fs/xfs/xfs_ioctl.c:345:18 index 1 is out of range for type '__s32 [1]' Call Trace: dump_stack_lvl+0x33/0x50 __ubsan_handle_out_of_bounds+0x9c/0xd0 xfs_ioc_attr_put_listent+0x413/0x420 [xfs 4a986a89a77bb77402ab8a87a37da369ef6a3f09] xfs_attr_list_ilocked+0x170/0x850 [xfs 4a986a89a77bb77402ab8a87a37da369ef6a3f09] xfs_attr_list+0xb7/0x120 [xfs 4a986a89a77bb77402ab8a87a37da369ef6a3f09] xfs_ioc_attr_list+0x13b/0x2e0 [xfs 4a986a89a77bb77402ab8a87a37da369ef6a3f09] xfs_attrlist_by_handle+0xab/0x120 [xfs 4a986a89a77bb77402ab8a87a37da369ef6a3f09] xfs_file_ioctl+0x1ff/0x15e0 [xfs 4a986a89a77bb77402ab8a87a37da369ef6a3f09] vfs_ioctl+0x1f/0x60 The kernel and xfsprogs code that uses these structures will not have problems, but the long tail of external user programs might. Signed-off-by: Darrick J. Wong --- fs/xfs/libxfs/xfs_fs.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h index 9c60ebb328b4..2cbf9ea39b8c 100644 --- a/fs/xfs/libxfs/xfs_fs.h +++ b/fs/xfs/libxfs/xfs_fs.h @@ -592,12 +592,12 @@ typedef struct xfs_attrlist_cursor { struct xfs_attrlist { __s32 al_count; /* number of entries in attrlist */ __s32 al_more; /* T/F: more attrs (do call again) */ - __s32 al_offset[1]; /* byte offsets of attrs [var-sized] */ + __s32 al_offset[]; /* byte offsets of attrs [var-sized] */ }; struct xfs_attrlist_ent { /* data from attr_list() */ __u32 a_valuelen; /* number bytes in value of attr */ - char a_name[1]; /* attr name (NULL terminated) */ + char a_name[]; /* attr name (NULL terminated) */ }; typedef struct xfs_fsop_attrlist_handlereq { From patchwork Fri Jul 14 14:42:30 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Darrick J. Wong" X-Patchwork-Id: 13313752 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6B894C0015E for ; Fri, 14 Jul 2023 14:42:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236126AbjGNOmj (ORCPT ); Fri, 14 Jul 2023 10:42:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53744 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236134AbjGNOmf (ORCPT ); Fri, 14 Jul 2023 10:42:35 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AF19535AC for ; Fri, 14 Jul 2023 07:42:32 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 0BAD161D30 for ; Fri, 14 Jul 2023 14:42:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 69A2FC433C8; Fri, 14 Jul 2023 14:42:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1689345751; bh=yRbcM3rSaR6qgTH9sRf6k8ylcZ6KhBjAjWjJ4eiKBhU=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=fVn8LihyNV76z4p+jGVAVLPkgVjEUKOASksM2fIeYjWkdmB0WtUYLoVRnsc4g7YZy T/4A4uZKQMxGPS9Vrr84sI2msvjm+EUaM+hoK2hoOOMkrFzUpoaNjgw5+pMkBsOG43 VwnCpHVGmXs9/kot9i43Jpqpk97cf5rVLmH1YsXvbDGA0p7jdrc3RzVlkpkJ7IK7FQ Vfppd9Q7FhC0zfkLffcYbaCmkIHBY2+zXxlIZyw/qrD+Te6sfJ9zln2qyhwQk+RgjS MAs5oOv/OXWHv/unHhrNk/L6TNo5DOHBVW06B6bZFu2MBpbKEA4Caq4HDQnvFKhjOv Z0btepPWF6KUA== Subject: [PATCH 2/3] xfs: convert flex-array declarations in xfs attr leaf blocks From: "Darrick J. Wong" To: david@fromorbit.com, djwong@kernel.org Cc: linux-xfs@vger.kernel.org, keescook@chromium.org Date: Fri, 14 Jul 2023 07:42:30 -0700 Message-ID: <168934575091.3353217.2520087245956820631.stgit@frogsfrogsfrogs> In-Reply-To: <168934573961.3353217.18139786322840965874.stgit@frogsfrogsfrogs> References: <168934573961.3353217.18139786322840965874.stgit@frogsfrogsfrogs> User-Agent: StGit/0.19 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org From: Darrick J. Wong As of 6.5-rc1, UBSAN trips over the ondisk extended attribute leaf block definitions using an array length of 1 to pretend to be a flex array. Kernel compilers have to support unbounded array declarations, so let's correct this. ================================================================================ UBSAN: array-index-out-of-bounds in fs/xfs/libxfs/xfs_attr_leaf.c:2535:24 index 2 is out of range for type '__u8 [1]' Call Trace: dump_stack_lvl+0x33/0x50 __ubsan_handle_out_of_bounds+0x9c/0xd0 xfs_attr3_leaf_getvalue+0x2ce/0x2e0 [xfs 4a986a89a77bb77402ab8a87a37da369ef6a3f09] xfs_attr_leaf_get+0x148/0x1c0 [xfs 4a986a89a77bb77402ab8a87a37da369ef6a3f09] xfs_attr_get_ilocked+0xae/0x110 [xfs 4a986a89a77bb77402ab8a87a37da369ef6a3f09] xfs_attr_get+0xee/0x150 [xfs 4a986a89a77bb77402ab8a87a37da369ef6a3f09] xfs_xattr_get+0x7d/0xc0 [xfs 4a986a89a77bb77402ab8a87a37da369ef6a3f09] __vfs_getxattr+0xa3/0x100 vfs_getxattr+0x87/0x1d0 do_getxattr+0x17a/0x220 getxattr+0x89/0xf0 Signed-off-by: Darrick J. Wong --- fs/xfs/libxfs/xfs_da_format.h | 73 +++++++++++++++++++++++++++++++++++++---- fs/xfs/xfs_ondisk.h | 4 +- 2 files changed, 67 insertions(+), 10 deletions(-) diff --git a/fs/xfs/libxfs/xfs_da_format.h b/fs/xfs/libxfs/xfs_da_format.h index 25e2841084e1..b2362717c42e 100644 --- a/fs/xfs/libxfs/xfs_da_format.h +++ b/fs/xfs/libxfs/xfs_da_format.h @@ -620,19 +620,29 @@ typedef struct xfs_attr_leaf_entry { /* sorted on key, not name */ typedef struct xfs_attr_leaf_name_local { __be16 valuelen; /* number of bytes in value */ __u8 namelen; /* length of name bytes */ - __u8 nameval[1]; /* name/value bytes */ + /* + * In Linux 6.5 this flex array was converted from nameval[1] to + * nameval[]. Be very careful here about extra padding at the end; + * see xfs_attr_leaf_entsize_local() for details. + */ + __u8 nameval[]; /* name/value bytes */ } xfs_attr_leaf_name_local_t; typedef struct xfs_attr_leaf_name_remote { __be32 valueblk; /* block number of value bytes */ __be32 valuelen; /* number of bytes in value */ __u8 namelen; /* length of name bytes */ - __u8 name[1]; /* name bytes */ + /* + * In Linux 6.5 this flex array was converted from name[1] to name[]. + * Be very careful here about extra padding at the end; see + * xfs_attr_leaf_entsize_remote() for details. + */ + __u8 name[]; /* name bytes */ } xfs_attr_leaf_name_remote_t; typedef struct xfs_attr_leafblock { xfs_attr_leaf_hdr_t hdr; /* constant-structure header block */ - xfs_attr_leaf_entry_t entries[1]; /* sorted on key, not name */ + xfs_attr_leaf_entry_t entries[]; /* sorted on key, not name */ /* * The rest of the block contains the following structures after the * leaf entries, growing from the bottom up. The variables are never @@ -664,7 +674,7 @@ struct xfs_attr3_leaf_hdr { struct xfs_attr3_leafblock { struct xfs_attr3_leaf_hdr hdr; - struct xfs_attr_leaf_entry entries[1]; + struct xfs_attr_leaf_entry entries[]; /* * The rest of the block contains the following structures after the @@ -747,14 +757,61 @@ xfs_attr3_leaf_name_local(xfs_attr_leafblock_t *leafp, int idx) */ static inline int xfs_attr_leaf_entsize_remote(int nlen) { - return round_up(sizeof(struct xfs_attr_leaf_name_remote) - 1 + - nlen, XFS_ATTR_LEAF_NAME_ALIGN); + /* + * Prior to Linux 6.5, struct xfs_attr_leaf_name_remote ended with + * name[1], which was used as a flexarray. The layout of this struct + * is 9 bytes of fixed-length fields followed by a __u8 flex array at + * offset 9. + * + * On most architectures, struct xfs_attr_leaf_name_remote had two + * bytes of implicit padding at the end of the struct to make the + * struct length 12. After converting name[1] to name[], there are + * three implicit padding bytes and the struct size remains 12. + * However, there are compiler configurations that do not add implicit + * padding at all (m68k) and have been broken for years. + * + * This entsize computation historically added (the xattr name length) + * to (the padded struct length - 1) and rounded that sum up to the + * nearest multiple of 4 (NAME_ALIGN). IOWs, round_up(11 + nlen, 4). + * This is encoded in the ondisk format, so we cannot change this. + * + * Compute the entsize from offsetof of the flexarray and manually + * adding bytes for the implicit padding. + */ + const size_t remotesize = + offsetof(struct xfs_attr_leaf_name_remote, name) + 2; + + return round_up(remotesize + nlen, XFS_ATTR_LEAF_NAME_ALIGN); } static inline int xfs_attr_leaf_entsize_local(int nlen, int vlen) { - return round_up(sizeof(struct xfs_attr_leaf_name_local) - 1 + - nlen + vlen, XFS_ATTR_LEAF_NAME_ALIGN); + /* + * Prior to Linux 6.5, struct xfs_attr_leaf_name_local ended with + * nameval[1], which was used as a flexarray. The layout of this + * struct is 3 bytes of fixed-length fields followed by a __u8 flex + * array at offset 3. + * + * struct xfs_attr_leaf_name_local had zero bytes of implicit padding + * at the end of the struct to make the struct length 4. On most + * architectures, after converting nameval[1] to nameval[], there is + * one implicit padding byte and the struct size remains 4. However, + * there are compiler configurations that do not add implicit padding + * at all (m68k) and would break. + * + * This entsize computation historically added (the xattr name and + * value length) to (the padded struct length - 1) and rounded that sum + * up to the nearest multiple of 4 (NAME_ALIGN). IOWs, the formula is + * round_up(3 + nlen + vlen, 4). This is encoded in the ondisk format, + * so we cannot change this. + * + * Compute the entsize from offsetof of the flexarray and manually + * adding bytes for the implicit padding. + */ + const size_t localsize = + offsetof(struct xfs_attr_leaf_name_local, nameval); + + return round_up(localsize + nlen + vlen, XFS_ATTR_LEAF_NAME_ALIGN); } static inline int xfs_attr_leaf_entsize_local_max(int bsize) diff --git a/fs/xfs/xfs_ondisk.h b/fs/xfs/xfs_ondisk.h index 9737b5a9f405..37be297f2532 100644 --- a/fs/xfs/xfs_ondisk.h +++ b/fs/xfs/xfs_ondisk.h @@ -56,7 +56,7 @@ xfs_check_ondisk_structs(void) /* dir/attr trees */ XFS_CHECK_STRUCT_SIZE(struct xfs_attr3_leaf_hdr, 80); - XFS_CHECK_STRUCT_SIZE(struct xfs_attr3_leafblock, 88); + XFS_CHECK_STRUCT_SIZE(struct xfs_attr3_leafblock, 80); XFS_CHECK_STRUCT_SIZE(struct xfs_attr3_rmt_hdr, 56); XFS_CHECK_STRUCT_SIZE(struct xfs_da3_blkinfo, 56); XFS_CHECK_STRUCT_SIZE(struct xfs_da3_intnode, 64); @@ -88,7 +88,7 @@ xfs_check_ondisk_structs(void) XFS_CHECK_OFFSET(xfs_attr_leaf_name_remote_t, valuelen, 4); XFS_CHECK_OFFSET(xfs_attr_leaf_name_remote_t, namelen, 8); XFS_CHECK_OFFSET(xfs_attr_leaf_name_remote_t, name, 9); - XFS_CHECK_STRUCT_SIZE(xfs_attr_leafblock_t, 40); + XFS_CHECK_STRUCT_SIZE(xfs_attr_leafblock_t, 32); XFS_CHECK_OFFSET(struct xfs_attr_shortform, hdr.totsize, 0); XFS_CHECK_OFFSET(struct xfs_attr_shortform, hdr.count, 2); XFS_CHECK_OFFSET(struct xfs_attr_shortform, list[0].namelen, 4); From patchwork Fri Jul 14 14:42:36 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Darrick J. Wong" X-Patchwork-Id: 13313753 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F03C5C0015E for ; Fri, 14 Jul 2023 14:42:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236124AbjGNOmo (ORCPT ); Fri, 14 Jul 2023 10:42:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54032 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236127AbjGNOmn (ORCPT ); Fri, 14 Jul 2023 10:42:43 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4660130E8 for ; Fri, 14 Jul 2023 07:42:38 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id A20CF61D30 for ; Fri, 14 Jul 2023 14:42:37 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0756CC433C7; Fri, 14 Jul 2023 14:42:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1689345757; bh=K23bJFCGkKB1J84q0TsjqBbL87WZJJj3kir0stOwC7g=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=jDjFJcSSuOeaKCwfHXjSg/OJUrM2V/bw3zRa1UBss3ZPYnA8gVk3nZh8vyMsFu40W lCn6Z6RbzHQw8mPkM+MKyiPGPnJ/cxY2QQ8TeZnLy176+tLtOTzeJUY8gSx2+O9pXv dOhBLEnEw4hDVsm10h0OfCxX5yvN6+VHdFg/70rJBSVfbD5Fbf7/AoY4bWb6iLSoyq P2xnYBvXMNCjADJ6DOIj0cMTdJqLNNYafODXQKDKC/6fwW3M/p7XpP2VLMoZ9itZTp y6vyysCkb089XoTtv37r05z+lHwl2FN9d66/e44msPWLVKBu1P+q2dPJNGau2uzzMi xLyoIHWU9C+Jg== Subject: [PATCH 3/3] xfs: convert flex-array declarations in xfs attr shortform objects From: "Darrick J. Wong" To: david@fromorbit.com, djwong@kernel.org Cc: linux-xfs@vger.kernel.org, keescook@chromium.org Date: Fri, 14 Jul 2023 07:42:36 -0700 Message-ID: <168934575659.3353217.14415944789032059368.stgit@frogsfrogsfrogs> In-Reply-To: <168934573961.3353217.18139786322840965874.stgit@frogsfrogsfrogs> References: <168934573961.3353217.18139786322840965874.stgit@frogsfrogsfrogs> User-Agent: StGit/0.19 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org From: Darrick J. Wong As of 6.5-rc1, UBSAN trips over the ondisk extended attribute shortform definitions using an array length of 1 to pretend to be a flex array. Kernel compilers have to support unbounded array declarations, so let's correct this. Signed-off-by: Darrick J. Wong --- fs/xfs/libxfs/xfs_da_format.h | 2 +- fs/xfs/xfs_ondisk.h | 1 + 2 files changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/xfs/libxfs/xfs_da_format.h b/fs/xfs/libxfs/xfs_da_format.h index b2362717c42e..f9015f88eca7 100644 --- a/fs/xfs/libxfs/xfs_da_format.h +++ b/fs/xfs/libxfs/xfs_da_format.h @@ -591,7 +591,7 @@ struct xfs_attr_shortform { uint8_t valuelen; /* actual length of value (no NULL) */ uint8_t flags; /* flags bits (see xfs_attr_leaf.h) */ uint8_t nameval[]; /* name & value bytes concatenated */ - } list[1]; /* variable sized array */ + } list[]; /* variable sized array */ }; typedef struct xfs_attr_leaf_map { /* RLE map of free bytes */ diff --git a/fs/xfs/xfs_ondisk.h b/fs/xfs/xfs_ondisk.h index 37be297f2532..c4cc99b70dd3 100644 --- a/fs/xfs/xfs_ondisk.h +++ b/fs/xfs/xfs_ondisk.h @@ -89,6 +89,7 @@ xfs_check_ondisk_structs(void) XFS_CHECK_OFFSET(xfs_attr_leaf_name_remote_t, namelen, 8); XFS_CHECK_OFFSET(xfs_attr_leaf_name_remote_t, name, 9); XFS_CHECK_STRUCT_SIZE(xfs_attr_leafblock_t, 32); + XFS_CHECK_STRUCT_SIZE(struct xfs_attr_shortform, 4); XFS_CHECK_OFFSET(struct xfs_attr_shortform, hdr.totsize, 0); XFS_CHECK_OFFSET(struct xfs_attr_shortform, hdr.count, 2); XFS_CHECK_OFFSET(struct xfs_attr_shortform, list[0].namelen, 4);