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