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 51853495518 for ; Thu, 3 Sep 2026 11:42:02 +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=1788435733; cv=none; b=TnIdaDZYWeyAZUxmSf8YHNzv5wf28I/VddRN+SVVgpx0dpuPRDfG1SavjkxarCxbMNEQoQwAWsPe2I3cll7NtzFOgbGq+1N3HK0p8BuZ2XwPOqZUxF9KpgpIQ90zKmdHTIpqhpDf7NX7odteF59+2sgmt5NIclxRdiURWYiB6mQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788435733; c=relaxed/simple; bh=omC1PaN+AyjRgj8T5oM4LbkFXe/dXINKoYAZYKhMWn4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=QMHucEuebytBMfcL0Gc0L4Z+NoUr8THYFOwJlSGIGS3Z2xxzg5MuEGKpfnQmjZlfkh45aBo5iRIMA4EiA/UMExwf+3Z7F/LDW5saFY1RGI48BY1pOqgy4aR7ny6q+mCDChqRpslVKeizgWdnkzze6/Vfwo1heiS82aWqZDBt0MU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=i2xuvv6N; 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="i2xuvv6N" Received: by smtp.kernel.org (Postfix) with ESMTPSA id ADFB21F00A3A; Thu, 3 Sep 2026 11:41:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788435718; bh=nSFK7mpw7crsDIQSQbKr/KMQK2nNGQKi7Ehdigr8Hzw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=i2xuvv6NDhkF9Hui5An3xoFlgCMkHudYahFQU2SsDnQd3nbmEARHpJjIJuJxcJTt1 vGYLMSQlMt0XseGcvNE6pP73056iE9uYsDoQk+yGPOOZfIJhO5n7PmQ6y/XQNJ+IEC SE+BPDyUw2TeCadhEX/ebkqriCcPnDw0tRfa7wueW8EPOaKhDi6KR90jcM/Kp4hjZ9 AmZEuxaiIpcHcZto80tGjOaEbZ1OoWAjcSiuTq/H+5sQLjQj5Zab1JBtTrpUs+2sbr 6FOy1tYJ54lwGCyODpxetwbkQJHZwJDLqasoIpNjbAaJ/3EqbX90JKAqHsJ00h17lH lGjL8PL3oN9+w== 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 v2 21/23] xfs: fix off-by-one in rtrefcount btree root level validation Date: Thu, 3 Sep 2026 13:40:03 +0200 Message-ID: <20260903114022.570210-22-aalbersh@kernel.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260903114022.570210-1-aalbersh@kernel.org> References: <20260903114022.570210-1-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