From 1fab7a4d22151968645c995bc62580f40ae566ce Mon Sep 17 00:00:00 2001 From: Julien Thierry Date: Fri, 2 Oct 2020 15:10:31 +0100 Subject: [RHEL8.2 KPATCH] [fs] xfs: fix boundary test in xfs_attr_shortform_verify Kernels: 4.18.0-193.el8 4.18.0-193.1.2.el8_2 4.18.0-193.6.3.el8_2 4.18.0-193.13.2.el8_2 4.18.0-193.14.3.el8_2 4.18.0-193.19.1.el8_2 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 def0a18dc3b157ec347f018c1b367d8e4825dfca Author: Eric Sandeen Date: Thu Sep 10 16:10:27 2020 -0300 [fs] xfs: fix boundary test in xfs_attr_shortform_verify Message-id: <5f3f90ef-7bec-6c66-8567-a2eb0a71a63c@redhat.com> Patchwork-id: 326142 Patchwork-instance: patchwork O-Subject: [PATCH RHEL8.3] xfs: fix boundary test in xfs_attr_shortform_verify Bugzilla: 1875316 Z-Bugzilla: 1881085 CVE: CVE-2020-14385 RH-Acked-by: Brian Foster RH-Acked-by: Vladis Dronov Bugzilla: 1875316 Upstream Status: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/ Build Info: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=31249120 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: Bruno Meneguele 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 cbcc400f7634..7dbca5a14a90 100644 --- a/fs/xfs/libxfs/xfs_attr_leaf.c +++ b/fs/xfs/libxfs/xfs_attr_leaf.c @@ -949,8 +949,10 @@ 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