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

[Kristian Høgsberg]

Looks good,

Reviewed-by: Kristian H. Kristensen <hoegsberg at google.com>

On Tue, Nov 12, 2019 at 10:47 AM Brian Paul <brianp at vmware.com> wrote:
>
> 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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