commit 06888d571b51 ("drm/amd/display: Avoid HDCP over-read and corruption")
fixed an overread with an invalid buffer length but added an unnecessary
buffer and copy.
Simplify the code by using a single uint64_t and __builtin_popcountll to
count the number of bits set in the original bksv buffer instead of a loop.
This also avoid a possible unaligned access of the temporary bksv.
Signed-off-by: Joe Perches <j...@perches.com>
---
It seems quite odd 20 bits set is a magic number here.
Should it be a specific be/le value instead?
drivers/gpu/drm/amd/display/modules/hdcp/hdcp1_execution.c | 11 ++---------
1 file changed, 2 insertions(+), 9 deletions(-)
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 de872e7958b06..78a4c6dd95d99 100644
--- a/drivers/gpu/drm/amd/display/modules/hdcp/hdcp1_execution.c
+++ b/drivers/gpu/drm/amd/display/modules/hdcp/hdcp1_execution.c
@@ -28,17 +28,10 @@
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(bksv, hdcp->auth.msg.hdcp1.bksv,
sizeof(hdcp->auth.msg.hdcp1.bksv));
- n = *(uint64_t *)bksv;
+ memcpy(&n, hdcp->auth.msg.hdcp1.bksv,
sizeof(hdcp->auth.msg.hdcp1.bksv));
- while (n) {
- count++;
- n &= (n - 1);
- }
- return (count == 20) ? MOD_HDCP_STATUS_SUCCESS :
+ return (__builtin_popcountll(n) == 20) ? MOD_HDCP_STATUS_SUCCESS :
MOD_HDCP_STATUS_HDCP1_INVALID_BKSV;
}
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