[Qemu-devel] [PATCH] 9pfs: use g_malloc0 to allocate space for xattr

[Qemu-devel] [PATCH] 9pfs: use g_malloc0 to allocate space for xattr

[P J P]

From: Prasad J Pandit <pjp@fedoraproject.org>

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>
---
 hw/9pfs/9p.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index 23ac7bb532..f8bbac251d 100644
--- 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);
-- 
2.13.6

Re: [Qemu-devel] [PATCH] 9pfs: use g_malloc0 to allocate space for xattr

[Greg Kurz]

On Wed,  4 Oct 2017 17:06:52 +0530
P J P <ppandit@redhat.com> wrote:

> From: Prasad J Pandit <pjp@fedoraproject.org>
> 
> 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.
> 

Applied to 9p-next.

Thanks.

> Reported-by: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
> ---
>  hw/9pfs/9p.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
> index 23ac7bb532..f8bbac251d 100644
> --- 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);