Call shmget() with permission 0600 instead of 0777
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@lists.freedesktop.org Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
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@@ -89,8 +89,9 @@ alloc_back_shm_ximage(XMesaBuffer b, GLuint width, GLuint height)
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return GL_FALSE;
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}
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/* 0600 = user read+write */
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b->shminfo.shmid = shmget(IPC_PRIVATE, b->backxrb->ximage->bytes_per_line
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* b->backxrb->ximage->height, IPC_CREAT|0777);
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* b->backxrb->ximage->height, IPC_CREAT | 0600);
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if (b->shminfo.shmid < 0) {
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_mesa_warning(NULL, "shmget failed while allocating back buffer.\n");
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XDestroyImage(b->backxrb->ximage);
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