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authorLinus Torvalds <torvalds@linux-foundation.org>2021-05-08 11:30:22 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-05-08 11:30:22 -0700
commitfec4d42724a1bf3dcba52307e55375fdb967b852 (patch)
treecb373b5fd967ea068c2cedaea2a345384682fadd
parent07db05638aa25ed66e6fc89b45f6773ef3e69396 (diff)
drm/i915/display: fix compiler warning about array overrun
intel_dp_check_mst_status() uses a 14-byte array to read the DPRX Event Status Indicator data, but then passes that buffer at offset 10 off as an argument to drm_dp_channel_eq_ok(). End result: there are only 4 bytes remaining of the buffer, yet drm_dp_channel_eq_ok() wants a 6-byte buffer. gcc-11 correctly warns about this case: drivers/gpu/drm/i915/display/intel_dp.c: In function ‘intel_dp_check_mst_status’: drivers/gpu/drm/i915/display/intel_dp.c:3491:22: warning: ‘drm_dp_channel_eq_ok’ reading 6 bytes from a region of size 4 [-Wstringop-overread] 3491 | !drm_dp_channel_eq_ok(&esi[10], intel_dp->lane_count)) { | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ drivers/gpu/drm/i915/display/intel_dp.c:3491:22: note: referencing argument 1 of type ‘const u8 *’ {aka ‘const unsigned char *’} In file included from drivers/gpu/drm/i915/display/intel_dp.c:38: include/drm/drm_dp_helper.h:1466:6: note: in a call to function ‘drm_dp_channel_eq_ok’ 1466 | bool drm_dp_channel_eq_ok(const u8 link_status[DP_LINK_STATUS_SIZE], | ^~~~~~~~~~~~~~~~~~~~ 6:14 elapsed This commit just extends the original array by 2 zero-initialized bytes, avoiding the warning. There may be some underlying bug in here that caused this confusion, but this is at least no worse than the existing situation that could use random data off the stack. Cc: Jani Nikula <jani.nikula@intel.com> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Dave Airlie <airlied@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--drivers/gpu/drm/i915/display/intel_dp.c13
1 files changed, 12 insertions, 1 deletions
diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index a560468765c0..6a2dee8cef1f 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -3474,7 +3474,18 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp)
drm_WARN_ON_ONCE(&i915->drm, intel_dp->active_mst_links < 0);
for (;;) {
- u8 esi[DP_DPRX_ESI_LEN] = {};
+ /*
+ * The +2 is because DP_DPRX_ESI_LEN is 14, but we then
+ * pass in "esi+10" to drm_dp_channel_eq_ok(), which
+ * takes a 6-byte array. So we actually need 16 bytes
+ * here.
+ *
+ * Somebody who knows what the limits actually are
+ * should check this, but for now this is at least
+ * harmless and avoids a valid compiler warning about
+ * using more of the array than we have allocated.
+ */
+ u8 esi[DP_DPRX_ESI_LEN+2] = {};
bool handled;
int retry;

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