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drm/amd/display: Avoid HDCP over-read and corruption

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[ 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>
This commit is contained in:
Kees Cook
2021-05-28 10:53:54 -07:00
committed by Greg Kroah-Hartman
parent 3c172f6e44
commit c5b518f4b9
1 changed files with 3 additions and 1 deletions
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4
drivers/gpu/drm/amd/display/modules/hdcp/hdcp1_execution.c
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@@ -29,8 +29,10 @@ static inline enum mod_hdcp_status validate_bksv(struct mod_hdcp *hdcp)
{ {
uint64_t n = 0; uint64_t n = 0;
uint8_t count = 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) { while (n) {
count++; count++;