From 4801d9a446569eb73191c8cb3b769aadcd3f0994 Mon Sep 17 00:00:00 2001 From: Julien Thierry Date: Fri, 30 Oct 2020 09:00:20 +0000 Subject: [PATCH] [fs] xfs: fix boundary test in xfs_attr_shortform_verify Kernels: 3.10.0-1160.el7 3.10.0-1160.2.1.el7 3.10.0-1160.2.2.el7 3.10.0-1160.6.1.el7 Changes since last build: arches: x86_64 ppc64le xfs_attr_leaf.o: changed function: xfs_attr_shortform_verify --------------------------- Modifications: None Testing: tried the commands in the commit message before and after the kpatch-patch. Without the kpatch-patch, the filesystem dies. commit b2f2f4aef9d49b0b9fd349f0376f5ffe735e5823 Author: Eric Sandeen Date: Wed Sep 9 22:17:43 2020 -0400 [fs] xfs: fix boundary test in xfs_attr_shortform_verify Message-id: <98c52b4e-9e63-55e1-5e8e-4f8d193b3762@redhat.com> Patchwork-id: 326026 Patchwork-instance: patchwork O-Subject: [PATCH RHEL7.9.z] xfs: fix boundary test in xfs_attr_shortform_verify Bugzilla: 1875317 CVE: CVE-2020-14385 RH-Acked-by: Carlos Maiolino RH-Acked-by: Brian Foster Bugzilla: 1875317 Upstream Status: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/ Build Info: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=31247080 Tested: With simple reproducer in commit + xfstests CVE: CVE-2020-14385 The boundary test for the fixed-offset parts of xfs_attr_sf_entry in xfs_attr_shortform_verify is off by one, because the variable array at the end is defined as nameval[1] not nameval[]. Hence we need to subtract 1 from the calculation. This can be shown by: # touch file # setfattr -n root.a file and verifications will fail when it's written to disk. This only matters for a last attribute which has a single-byte name and no value, otherwise the combination of namelen & valuelen will push endp further out and this test won't fail. Fixes: 1e1bbd8e7ee06 ("xfs: create structure verifier function for shortform xattrs") Signed-off-by: Eric Sandeen Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong Reviewed-by: Christoph Hellwig (cherry picked from commit f4020438fab05364018c91f7e02ebdd192085933) Signed-off-by: Eric Sandeen Signed-off-by: Augusto Caringi Signed-off-by: Julien Thierry --- fs/xfs/libxfs/xfs_attr_leaf.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c index 2c892846929..1d2bedd4c1a 100644 --- a/fs/xfs/libxfs/xfs_attr_leaf.c +++ b/fs/xfs/libxfs/xfs_attr_leaf.c @@ -923,8 +923,10 @@ xfs_attr_shortform_verify( * struct xfs_attr_sf_entry has a variable length. * Check the fixed-offset parts of the structure are * within the data buffer. + * xfs_attr_sf_entry is defined with a 1-byte variable + * array at the end, so we must subtract that off. */ - if (((char *)sfep + sizeof(*sfep)) >= endp) + if (((char *)sfep + sizeof(*sfep) - 1) >= endp) return __this_address; /* Don't allow names with known bad length. */ -- 2.25.4