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 193AD27AC31 for ; Mon, 24 Aug 2026 11:47:00 +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=1787572022; cv=none; b=HgT6T0SVIsHFlaJ8iHhJdd1e4URoCWu6qUL2RguRpN0o5w9H29d0Tr7smkNzYtoQ6aGLpYX4HhcCJwakN4qG8aGC5sevUO+rwdb1fldZjFVyu7n95M5RvAjxMh1WSH1quVm/HkWCWJ8TYDSACA7XTllAzH7I+K4kmiPa3C0QQTA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787572022; c=relaxed/simple; bh=omC1PaN+AyjRgj8T5oM4LbkFXe/dXINKoYAZYKhMWn4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SyFL4CKwyXGHcAoe+16ATncs83epkt4HnZ2lxVYR0HJsp3owVqz+uef0SsyvGffGQQfoLVep8ks9Nsv4NQd0xoIspXwLKmqroPVFwm1m93ZOcpTrYQ1CC+YpiUZVT4SEHfm9Up1To8plo6bk/L2te49YV2O4dJ5UQb88ONRCotE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JIZdXulY; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="JIZdXulY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 75E381F000E9; Mon, 24 Aug 2026 11:46:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787572020; bh=nSFK7mpw7crsDIQSQbKr/KMQK2nNGQKi7Ehdigr8Hzw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=JIZdXulYq5uLNZbyy5dovU3nDdpqbA+vvWUqzMKwXiv1ocbmAySABPawiHZZJET09 Kl7Jic0xJU1wAXpeEEzR8ElB176De1YBRTLwCFM70Uka4/LnuIhBcOli5CR2DWZunX 5hnUCA6yZB0ErBoLbh/Wyq21/9oCLK/o9bc5hkIDkAm6TF05sPcFi4hz0ZxXQm1SPh dXORhgxRdQ2JhAleHKcwH9BgPbWU/HHs0N+kO5y7cGa9qd6JOW9tcGlFx8bgN5Wu01 /4mxrPGqt1fqwzdpBCbnTdWfHbG7x0YRM+0wdVsiYYs85ZkAwVYHe5Vi2H1AVk0AU4 5yGHxgi/9/ZGw== From: Andrey Albershteyn To: linux-xfs@vger.kernel.org, aalbersh@kernel.org Cc: bestswngs@gmail.com, brauner@kernel.org, cem@kernel.org, chuck.lever@oracle.com, cmaiolino@redhat.com, dawei.feng@seu.edu.cn, djwong@kernel.org, gaoyingjie@uniontech.com, hch@lst.de, jiapenglin@tencent.com, roland.mainz@nrubsig.org, xmei5@asu.edu Subject: [PATCH 19/21] xfs: fix off-by-one in rtrefcount btree root level validation Date: Mon, 24 Aug 2026 12:40:17 +0200 Message-ID: <20260824104022.420566-20-aalbersh@kernel.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260824104022.420566-1-aalbersh@kernel.org> References: <20260824104022.420566-1-aalbersh@kernel.org> Precedence: bulk X-Mailing-List: linux-xfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Xiang Mei Source kernel commit: cc3144da377de5fb422d44a2311f978623f7c900 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 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 --- libxfs/xfs_rtrefcount_btree.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/libxfs/xfs_rtrefcount_btree.c b/libxfs/xfs_rtrefcount_btree.c index 2c51b618e1ce..02230c8ef0f0 100644 --- a/libxfs/xfs_rtrefcount_btree.c +++ b/libxfs/xfs_rtrefcount_btree.c @@ -199,7 +199,7 @@ 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]); @@ -649,7 +649,7 @@ 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; -- 2.55.0