9pfs: use g_malloc0 to allocate space for xattr

9p back-end first queries the size of an extended attribute,
allocates space for it via g_malloc() and then retrieves its
value into allocated buffer. Race between querying attribute
size and retrieving its could lead to memory bytes disclosure.
Use g_malloc0() to avoid it.

Reported-by: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Signed-off-by: Greg Kurz <groug@kaod.org>

diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index 23ac7bb532f0dda38e7de61f8f6f017d8f0c2e42..f8bbac251dc96c83c99c74602444e7d2cfc9124f 100644 (file)
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -3234,7 +3234,7 @@ static void coroutine_fn v9fs_xattrwalk(void *opaque)
         xattr_fidp->fid_type = P9_FID_XATTR;
         xattr_fidp->fs.xattr.xattrwalk_fid = true;
         if (size) {
-            xattr_fidp->fs.xattr.value = g_malloc(size);
+            xattr_fidp->fs.xattr.value = g_malloc0(size);
             err = v9fs_co_llistxattr(pdu, &xattr_fidp->path,
                                      xattr_fidp->fs.xattr.value,
                                      xattr_fidp->fs.xattr.len);
@@ -3267,7 +3267,7 @@ static void coroutine_fn v9fs_xattrwalk(void *opaque)
         xattr_fidp->fid_type = P9_FID_XATTR;
         xattr_fidp->fs.xattr.xattrwalk_fid = true;
         if (size) {
-            xattr_fidp->fs.xattr.value = g_malloc(size);
+            xattr_fidp->fs.xattr.value = g_malloc0(size);
             err = v9fs_co_lgetxattr(pdu, &xattr_fidp->path,
                                     &name, xattr_fidp->fs.xattr.value,
                                     xattr_fidp->fs.xattr.len);