ext4: CVE-2018-1095

ext4: limit xattr size to INT_MAX

Reference:
https://nvd.nist.gov/vuln/detail/CVE-2018-1095
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-4.14.y&id=a57eb14b740e6175aff8b8941bec628403992dfa

Change-Id: I90e88ed42d43abb205c025cc3739a6030adfcb3f
Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>

1 files changed, 59 insertions, 0 deletions

diff --git a/patches/cve/CVE-2018-1095-ext4-limit-xattr-size-to-INT_MAX.patch b/patches/cve/CVE-2018-1095-ext4-limit-xattr-size-to-INT_MAX.patch
new file mode 100644
index 0000000..3725db6
--- /dev/null
+++ b/patches/cve/CVE-2018-1095-ext4-limit-xattr-size-to-INT_MAX.patch
@@ -0,0 +1,59 @@
+From a57eb14b740e6175aff8b8941bec628403992dfa Mon Sep 17 00:00:00 2001
+From: Eric Biggers <ebiggers@google.com>
+Date: Thu, 29 Mar 2018 14:31:42 -0400
+Subject: [PATCH] ext4: limit xattr size to INT_MAX
+
+commit ce3fd194fcc6fbdc00ce095a852f22df97baa401 upstream.
+
+ext4 isn't validating the sizes of xattrs where the value of the xattr
+is stored in an external inode.  This is problematic because
+->e_value_size is a u32, but ext4_xattr_get() returns an int.  A very
+large size is misinterpreted as an error code, which ext4_get_acl()
+translates into a bogus ERR_PTR() for which IS_ERR() returns false,
+causing a crash.
+
+Fix this by validating that all xattrs are <= INT_MAX bytes.
+
+This issue has been assigned CVE-2018-1095.
+
+https://bugzilla.kernel.org/show_bug.cgi?id=199185
+https://bugzilla.redhat.com/show_bug.cgi?id=1560793
+
+CVE: CVE-2018-1095
+Upstream-Status: Backport [https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-4.14.y&id=a57eb14b740e6175aff8b8941bec628403992dfa]
+
+Reported-by: Wen Xu <wen.xu@gatech.edu>
+Signed-off-by: Eric Biggers <ebiggers@google.com>
+Signed-off-by: Theodore Ts'o <tytso@mit.edu>
+Cc: stable@vger.kernel.org
+Fixes: e50e5129f384 ("ext4: xattr-in-inode support")
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>
+---
+ fs/ext4/xattr.c | 9 ++++++---
+ 1 file changed, 6 insertions(+), 3 deletions(-)
+
+diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
+index 218a7ba57819..5d0f5ba5c6f5 100644
+--- a/fs/ext4/xattr.c
++++ b/fs/ext4/xattr.c
+@@ -194,10 +194,13 @@ ext4_xattr_check_entries(struct ext4_xattr_entry *entry, void *end,
+ 
+        /* Check the values */
+        while (!IS_LAST_ENTRY(entry)) {
+-               if (entry->e_value_size != 0 &&
+-                   entry->e_value_inum == 0) {
++               u32 size = le32_to_cpu(entry->e_value_size);
++
++               if (size > INT_MAX)
++                       return -EFSCORRUPTED;
++
++               if (size != 0 && entry->e_value_inum == 0) {
+                        u16 offs = le16_to_cpu(entry->e_value_offs);
+-                       u32 size = le32_to_cpu(entry->e_value_size);
+                        void *value;
+ 
+                        /*
+-- 
+2.20.1
+