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[5.10,047/215] drm/amd/display: Avoid HDCP over-read and corruption

Message ID 20210715182607.713417088@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg KH July 15, 2021, 6:36 p.m. UTC 
From: Kees Cook <keescook@chromium.org>

[ Upstream commit 06888d571b513cbfc0b41949948def6cb81021b2 ]

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>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/gpu/drm/amd/display/modules/hdcp/hdcp1_execution.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
diff mbox series

Patch

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 f244b72e74e0..53eab2b8e2c8 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++;