debian/patches/extra/CVE-2016-8578-9pfs-allocate-space-for-guest-originated-empty-strin.patch

   1 From 630abd0c70f272b36361348e9ee7d6a71577b72f Mon Sep 17 00:00:00 2001
   2 From: Li Qiang <liqiang6-s@360.cn>
   3 Date: Tue, 11 Oct 2016 09:27:45 +0200
   4 Subject: [PATCH 4/4] 9pfs: allocate space for guest originated empty strings
   5
   6 If a guest sends an empty string paramater to any 9P operation, the current
   7 code unmarshals it into a V9fsString equal to { .size = 0, .data = NULL }.
   8
   9 This is unfortunate because it can cause NULL pointer dereference to happen
  10 at various locations in the 9pfs code. And we don't want to check str->data
  11 everywhere we pass it to strcmp() or any other function which expects a
  12 dereferenceable pointer.
  13
  14 This patch enforces the allocation of genuine C empty strings instead, so
  15 callers don't have to bother.
  16
  17 Out of all v9fs_iov_vunmarshal() users, only v9fs_xattrwalk() checks if
  18 the returned string is empty. It now uses v9fs_string_size() since
  19 name.data cannot be NULL anymore.
  20
  21 Signed-off-by: Li Qiang <liqiang6-s@360.cn>
  22 [groug, rewritten title and changelog,
  23  fix empty string check in v9fs_xattrwalk()]
  24 Signed-off-by: Greg Kurz <groug@kaod.org>
  25 ---
  26  fsdev/9p-iov-marshal.c | 2 +-
  27  hw/9pfs/9p.c           | 2 +-
  28  2 files changed, 2 insertions(+), 2 deletions(-)
  29
  30 diff --git a/fsdev/9p-iov-marshal.c b/fsdev/9p-iov-marshal.c
  31 index 663cad5..1d16f8d 100644
  32 --- a/fsdev/9p-iov-marshal.c
  33 +++ b/fsdev/9p-iov-marshal.c
  34 @@ -125,7 +125,7 @@ ssize_t v9fs_iov_vunmarshal(struct iovec *out_sg, int out_num, size_t offset,
  35                  str->data = g_malloc(str->size + 1);
  36                  copied = v9fs_unpack(str->data, out_sg, out_num, offset,
  37                                       str->size);
  38 -                if (copied > 0) {
  39 +                if (copied >= 0) {
  40                      str->data[str->size] = 0;
  41                  } else {
  42                      v9fs_string_free(str);
  43 diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
  44 index 54e18a2..75ba5f1 100644
  45 --- a/hw/9pfs/9p.c
  46 +++ b/hw/9pfs/9p.c
  47 @@ -3161,7 +3161,7 @@ static void v9fs_xattrwalk(void *opaque)
  48          goto out;
  49      }
  50      v9fs_path_copy(&xattr_fidp->path, &file_fidp->path);
  51 -    if (name.data == NULL) {
  52 +    if (!v9fs_string_size(&name)) {
  53          /*
  54           * listxattr request. Get the size first
  55           */
  56 --
  57 2.1.4
  58