Mesa (main): virgl: disallow null-terminated debug messages

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Module: Mesa
Branch: main
Commit: 0972b0f7547fe9956a1b5a5cbfda38a0fd996fa6
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=0972b0f7547fe9956a1b5a5cbfda38a0fd996fa6

Author: Ryan Neph <ryanneph at google.com>
Date:   Fri Jul 23 10:27:03 2021 -0700

virgl: disallow null-terminated debug messages

virglrenderer doesn't support null-terminated message strings, so
there's no reason for the guest to allow it.

Signed-off-by: Ryan Neph <ryanneph at google.com>
Reviewed-by: Chia-I Wu <olvaffe at gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12043>

---

 src/gallium/drivers/virgl/virgl_encode.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/gallium/drivers/virgl/virgl_encode.c b/src/gallium/drivers/virgl/virgl_encode.c
index 41b471e8e09..01e5637f5bf 100644
--- a/src/gallium/drivers/virgl/virgl_encode.c
+++ b/src/gallium/drivers/virgl/virgl_encode.c
@@ -1536,7 +1536,9 @@ void virgl_encode_get_memory_info(struct virgl_context *ctx, struct virgl_resour
 void virgl_encode_emit_string_marker(struct virgl_context *ctx,
                                      const char *message, int len)
 {
-    if (!len)
+   /* len is guaranteed to be non-negative but be defensive */
+   assert(len >= 0);
+   if (len <= 0)
       return;
 
    if (len > 4 * 0xffff) {