jfs: Fix inconsistency between memory allocation and ea_buf->max_size (CVE-2018-12233)

debian/changelog

@@ -107,6 +107,8 @@ linux (4.17.3-1) UNRELEASED; urgency=medium
   * ext4: avoid running out of journal credits when appending to an inline file
     (CVE-2018-10883)
   * ext4: add more inode number paranoia checks (CVE-2018-10882)
+  * jfs: Fix inconsistency between memory allocation and ea_buf->max_size
+    (CVE-2018-12233)
 
   [ Romain Perier ]
   * [x86] amdgpu: Enable DCN 1.0 Raven family (Closes: #901349)

debian/patches/bugfix/all/jfs-fix-inconsistency-between-memory-allocation-and-.patch

@@ -0,0 +1,39 @@
+From: Shankara Pailoor <shankarapailoor@gmail.com>
+Date: Tue, 5 Jun 2018 08:33:27 -0500
+Subject: jfs: Fix inconsistency between memory allocation and ea_buf->max_size
+Origin: https://git.kernel.org/linus/92d34134193e5b129dc24f8d79cb9196626e8d7a
+Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2018-12233
+
+The code is assuming the buffer is max_size length, but we weren't
+allocating enough space for it.
+
+Signed-off-by: Shankara Pailoor <shankarapailoor@gmail.com>
+Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
+---
+ fs/jfs/xattr.c | 10 ++++++----
+ 1 file changed, 6 insertions(+), 4 deletions(-)
+
+--- a/fs/jfs/xattr.c
++++ b/fs/jfs/xattr.c
+@@ -491,15 +491,17 @@ static int ea_get(struct inode *inode, s
+ 	if (size > PSIZE) {
+ 		/*
+ 		 * To keep the rest of the code simple.  Allocate a
+-		 * contiguous buffer to work with
++		 * contiguous buffer to work with. Make the buffer large
++		 * enough to make use of the whole extent.
+ 		 */
+-		ea_buf->xattr = kmalloc(size, GFP_KERNEL);
++		ea_buf->max_size = (size + sb->s_blocksize - 1) &
++		    ~(sb->s_blocksize - 1);
++
++		ea_buf->xattr = kmalloc(ea_buf->max_size, GFP_KERNEL);
+ 		if (ea_buf->xattr == NULL)
+ 			return -ENOMEM;
+ 
+ 		ea_buf->flag = EA_MALLOC;
+-		ea_buf->max_size = (size + sb->s_blocksize - 1) &
+-		    ~(sb->s_blocksize - 1);
+ 
+ 		if (ea_size == 0)
+ 			return 0;

debian/patches/series

@@ -144,6 +144,7 @@ bugfix/all/ext4-never-move-the-system.data-xattr-out-of-the-ino.patch
 bugfix/all/jbd2-don-t-mark-block-as-modified-if-the-handle-is-o.patch
 bugfix/all/ext4-avoid-running-out-of-journal-credits-when-appen.patch
 bugfix/all/ext4-add-more-inode-number-paranoia-checks.patch
+bugfix/all/jfs-fix-inconsistency-between-memory-allocation-and-.patch
 
 # Fix exported symbol versions
 bugfix/all/module-disable-matching-missing-version-crc.patch