6.6-stable review patch. If anyone has any objections, please let me know.
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From: Douglas Anderson dianders@chromium.org
[ Upstream commit 3164c8a70073d43629b4e11e083d3d2798f7750f ]
While testing, I happened to notice a random crash that looked like:
Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: drm_dp_dpcd_probe+0x120/0x120
Analysis of drm_dp_dpcd_probe() shows that we pass in a 1-byte buffer (allocated on the stack) to the aux->transfer() function. Presumably if the aux->transfer() writes more than one byte to this buffer then we're in a bad shape.
Dropping into kgdb, I noticed that "aux->transfer" pointed at ps8640_aux_transfer().
Reading through ps8640_aux_transfer(), I can see that there are cases where it could write more bytes to msg->buffer than were specified by msg->size. This could happen if the hardware reported back something bogus to us. Let's fix this so we never write more than msg->size bytes. We'll still read all the bytes from the hardware just in case the hardware requires it since the aux transfer data comes through an auto-incrementing register.
NOTE: I have no actual way to reproduce this issue but it seems likely this is what was happening in the crash I looked at.
Fixes: 13afcdd7277e ("drm/bridge: parade-ps8640: Add support for AUX channel") Reviewed-by: Stephen Boyd swboyd@chromium.org Reviewed-by: Guenter Roeck groeck@chromium.org Signed-off-by: Douglas Anderson dianders@chromium.org Link: https://patchwork.freedesktop.org/patch/msgid/20231214123752.v3.1.I9d1afcaad... Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/bridge/parade-ps8640.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c index 8161b1a1a4b12..d264b80d909de 100644 --- a/drivers/gpu/drm/bridge/parade-ps8640.c +++ b/drivers/gpu/drm/bridge/parade-ps8640.c @@ -330,11 +330,12 @@ static ssize_t ps8640_aux_transfer_msg(struct drm_dp_aux *aux, return ret; }
- buf[i] = data; + if (i < msg->size) + buf[i] = data; } }
- return len; + return min(len, msg->size); }
static ssize_t ps8640_aux_transfer(struct drm_dp_aux *aux,