[Mesa-dev] [PATCH] Call shmget() with permission 0600 instead of 0777

[Brian Paul]

Ping again.


On 10/24/2019 03:25 PM, Brian Paul wrote:
> Ping.  Anyone?
> 
> -Brian
> 
> On Tue, Oct 22, 2019 at 3:52 PM Brian Paul <brianp at vmware.com 
> <mailto:brianp at vmware.com>> wrote:
> 
>     A security advisory (TALOS-2019-0857/CVE-2019-5068) found that
>     creating shared memory regions with permission mode 0777 could allow
>     any user to access that memory.  Several Mesa drivers use shared-
>     memory XImages to implement back buffers for improved performance.
> 
>     This path changes the shmget() calls to use 0600 (user r/w).
> 
>     Tested with legacy Xlib driver and llvmpipe.
> 
>     Cc: mesa-stable at lists.freedesktop.org
>     <mailto:mesa-stable at lists.freedesktop.org>
>     ---
>       src/gallium/winsys/sw/dri/dri_sw_winsys.c   | 3 ++-
>       src/gallium/winsys/sw/xlib/xlib_sw_winsys.c | 3 ++-
>       src/mesa/drivers/x11/xm_buffer.c            | 3 ++-
>       3 files changed, 6 insertions(+), 3 deletions(-)
> 
>     diff --git a/src/gallium/winsys/sw/dri/dri_sw_winsys.c
>     b/src/gallium/winsys/sw/dri/dri_sw_winsys.c
>     index 761f5d1..2e5970b 100644
>     --- a/src/gallium/winsys/sw/dri/dri_sw_winsys.c
>     +++ b/src/gallium/winsys/sw/dri/dri_sw_winsys.c
>     @@ -92,7 +92,8 @@ alloc_shm(struct dri_sw_displaytarget *dri_sw_dt,
>     unsigned size)
>       {
>          char *addr;
> 
>     -   dri_sw_dt->shmid = shmget(IPC_PRIVATE, size, IPC_CREAT|0777);
>     +   /* 0600 = user read+write */
>     +   dri_sw_dt->shmid = shmget(IPC_PRIVATE, size, IPC_CREAT | 0600);
>          if (dri_sw_dt->shmid < 0)
>             return NULL;
> 
>     diff --git a/src/gallium/winsys/sw/xlib/xlib_sw_winsys.c
>     b/src/gallium/winsys/sw/xlib/xlib_sw_winsys.c
>     index c14c9de..edebb48 100644
>     --- a/src/gallium/winsys/sw/xlib/xlib_sw_winsys.c
>     +++ b/src/gallium/winsys/sw/xlib/xlib_sw_winsys.c
>     @@ -126,7 +126,8 @@ alloc_shm(struct xlib_displaytarget *buf,
>     unsigned size)
>          shminfo->shmid = -1;
>          shminfo->shmaddr = (char *) -1;
> 
>     -   shminfo->shmid = shmget(IPC_PRIVATE, size, IPC_CREAT|0777);
>     +   /* 0600 = user read+write */
>     +   shminfo->shmid = shmget(IPC_PRIVATE, size, IPC_CREAT | 0600);
>          if (shminfo->shmid < 0) {
>             return NULL;
>          }
>     diff --git a/src/mesa/drivers/x11/xm_buffer.c
>     b/src/mesa/drivers/x11/xm_buffer.c
>     index d945d8a..0da08a6 100644
>     --- a/src/mesa/drivers/x11/xm_buffer.c
>     +++ b/src/mesa/drivers/x11/xm_buffer.c
>     @@ -89,8 +89,9 @@ alloc_back_shm_ximage(XMesaBuffer b, GLuint width,
>     GLuint height)
>             return GL_FALSE;
>          }
> 
>     +   /* 0600 = user read+write */
>          b->shminfo.shmid = shmget(IPC_PRIVATE,
>     b->backxrb->ximage->bytes_per_line
>     -                            * b->backxrb->ximage->height,
>     IPC_CREAT|0777);
>     +                             * b->backxrb->ximage->height,
>     IPC_CREAT | 0600);
>          if (b->shminfo.shmid < 0) {
>             _mesa_warning(NULL, "shmget failed while allocating back
>     buffer.\n");
>             XDestroyImage(b->backxrb->ximage);
>     -- 
>     1.8.5.6
> 
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