From: Kees Cook Date: Fri, 28 May 2021 17:53:54 +0000 (-0700) Subject: drm/amd/display: Avoid HDCP over-read and corruption X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=06888d571b513cbfc0b41949948def6cb81021b2;p=linux.git drm/amd/display: Avoid HDCP over-read and corruption 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 Signed-off-by: Alex Deucher --- 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 43e6f8b17e79c..de872e7958b06 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++;