From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 651DA37C925; Thu, 20 Aug 2026 15:06:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787238377; cv=none; b=HRhBaMWyojokkEFxo7u/EWB9XJhZPrwfwcG/4lr5sCunzTnKVxqzY9TQDZTV4zpWFlGNsLWA32X6ksgoyIHqYiJMxipfjdOukzuF9MnW31Cx4MOgkx4h+VzF4owi576ibm7tJuvg6Nr3uqdB+/foeUX+nJuhIBN08wHPr3+6UUs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787238377; c=relaxed/simple; bh=mPnpovqvv7OpgOQuQcXmK3rtYx2FIgdc7FMaP0WqjjY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uTSo1usizUy9goip273fgx32OuO8JKXgBCaep1hWGgdaLcak8QtE7xEE245V2RHuk7SaKXKjvykWAZbahsVKG5Mc+ZezmwhxmuPliaPsBcqkE4LPT5xgRMwxNtolGOU+eEblbkeHZoBFcCCT+kFfOdiJbYO04g5to8vXbZJi8Hs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=qoCBXg0K; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="qoCBXg0K" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B6F3F1F000E9; Thu, 20 Aug 2026 15:06:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1787238376; bh=sVPZ0XBiheoMC1bJFvrLgF/NefGkwvcfBdFtzoFTQmU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=qoCBXg0Kx9kZJVd+CAlYdZ2hRckqvFzzmJ5l9SopYyghEv/q69isPfuGMvGUPBRGL b7ehhJcHndTC9leIvr3wRKTaHztdplLLluE9qyBw3Jkz9acjm/84dPVdkQLe8edLrt Te2moVq5p/hpyA+feK+30xf6RVO+G+1hy4A1DvdI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Weiming Shi , Xiang Mei , "Darrick J. Wong" , Christoph Hellwig , Carlos Maiolino Subject: [PATCH 7.1 126/228] xfs: fix off-by-one in rtrefcount btree root level validation Date: Thu, 20 Aug 2026 16:54:28 +0200 Message-ID: <20260820145248.447083455@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260820145244.450574346@linuxfoundation.org> References: <20260820145244.450574346@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Xiang Mei commit cc3144da377de5fb422d44a2311f978623f7c900 upstream. xfs_rtrefcountbt_compute_maxlevels() sets mp->m_rtrefc_maxlevels = min(d_maxlevels, r_maxlevels) + 1; where the trailing "+ 1" already accounts for the inode-root level, so the deepest valid on-disk root level is m_rtrefc_maxlevels - 1 and a cursor must satisfy bc_nlevels <= bc_maxlevels (= m_rtrefc_maxlevels). The two on-disk validation paths, xfs_rtrefcountbt_verify() and xfs_iformat_rtrefcount(), check the root level with ">" instead of ">=", so a crafted rtreflink (metadir + realtime + reflink) image whose /rtgroups/N.refcount inode has bb_level == m_rtrefc_maxlevels is accepted on mount. xfs_rtrefcountbt_init_cursor() then sets bc_nlevels = bb_level + 1, exceeding bc_maxlevels by one. Since the xfs_rtrefcountbt_cur slab object is sized for exactly bc_maxlevels entries, the first btree op on such a cursor indexes bc_levels[m_rtrefc_maxlevels] past the end of the object. This is reached by the first rtrefcount cursor built after mount, via log/CoW recovery (xfs_reflink_recover_cow() during xfs_mountfs()) or an FS_IOC_GETFSMAP over the realtime device. Reject a root level equal to m_rtrefc_maxlevels, matching the ">=" form already used by the sibling data-device refcount/rmap verifiers and the in-memory rtrmap verifier. BUG: KASAN: slab-out-of-bounds in xfs_btree_lookup (fs/xfs/libxfs/xfs_btree.c:2101) Write of size 2 at addr ffff888018391658 by task exploit/144 xfs_btree_lookup (fs/xfs/libxfs/xfs_btree.c:2101) xfs_btree_query_range (fs/xfs/libxfs/xfs_btree.c:5308) xfs_refcount_recover_cow_leftovers (fs/xfs/libxfs/xfs_refcount.c:2113) xfs_reflink_recover_cow (fs/xfs/xfs_reflink.c:1085) xlog_recover_finish (fs/xfs/xfs_log_recover.c:3551) xfs_mountfs (fs/xfs/xfs_mount.c:1158) xfs_fs_fill_super (fs/xfs/xfs_super.c:1940) get_tree_bdev_flags (fs/super.c:1634) vfs_get_tree (fs/super.c:1694) path_mount (fs/namespace.c:4161) __x64_sys_mount (fs/namespace.c:4367) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) The buggy address belongs to the cache xfs_rtrefcountbt_cur of size 216 The buggy address is located 8 bytes to the right of allocated 216-byte region [ffff888018391578, ffff888018391650) Kernel panic - not syncing: Fatal exception Cc: stable@vger.kernel.org # v6.14 Fixes: 9abe03a0e4f978 ("xfs: introduce realtime refcount btree ondisk definitions") Reported-by: Weiming Shi Signed-off-by: Xiang Mei Reviewed-by: "Darrick J. Wong" Reviewed-by: Christoph Hellwig Signed-off-by: Carlos Maiolino Signed-off-by: Greg Kroah-Hartman --- fs/xfs/libxfs/xfs_rtrefcount_btree.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/fs/xfs/libxfs/xfs_rtrefcount_btree.c +++ b/fs/xfs/libxfs/xfs_rtrefcount_btree.c @@ -201,7 +201,7 @@ xfs_rtrefcountbt_verify( if (fa) return fa; level = be16_to_cpu(block->bb_level); - if (level > mp->m_rtrefc_maxlevels) + if (level >= mp->m_rtrefc_maxlevels) return __this_address; return xfs_btree_fsblock_verify(bp, mp->m_rtrefc_mxr[level != 0]); @@ -651,7 +651,7 @@ xfs_iformat_rtrefcount( numrecs = be16_to_cpu(dfp->bb_numrecs); level = be16_to_cpu(dfp->bb_level); - if (level > mp->m_rtrefc_maxlevels || + if (level >= mp->m_rtrefc_maxlevels || xfs_rtrefcount_droot_space_calc(level, numrecs) > dsize) { xfs_inode_mark_sick(ip, XFS_SICK_INO_CORE); return -EFSCORRUPTED;