On Fri, May 28, 2021 at 1:54 PM Kees Cook keescook@chromium.org wrote:

Instead of reading the desired 5 bytes of the actual target field, the code was reading 8. This could result in a corrupted value if the trailing 3 bytes were non-zero, so instead use an appropriately sized and zero-initialized bounce buffer, and read only 5 bytes before casting to u64.

Signed-off-by: Kees Cook keescook@chromium.org

Applied. Thanks!

---

drivers/gpu/drm/amd/display/modules/hdcp/hdcp1_execution.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/modules/hdcp/hdcp1_execution.c b/drivers/gpu/drm/amd/display/modules/hdcp/hdcp1_execution.c index 2cbd931363bd..6d26d9c63ab2 100644 --- a/drivers/gpu/drm/amd/display/modules/hdcp/hdcp1_execution.c +++ b/drivers/gpu/drm/amd/display/modules/hdcp/hdcp1_execution.c @@ -29,8 +29,10 @@ static inline enum mod_hdcp_status validate_bksv(struct mod_hdcp *hdcp) { uint64_t n = 0; uint8_t count = 0;

•   u8 bksv[sizeof(n)] = { };
  
  

•   memcpy(&n, hdcp->auth.msg.hdcp1.bksv, sizeof(uint64_t));
  

•   memcpy(bksv, hdcp->auth.msg.hdcp1.bksv, sizeof(hdcp->auth.msg.hdcp1.bksv));
  

•   n = *(uint64_t *)bksv;
  
    while (n) {
            count++;
  

-- 2.25.1