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author | Douglas Anderson <dianders@chromium.org> | 2023-12-14 12:37:51 -0800 |
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committer | Douglas Anderson <dianders@chromium.org> | 2023-12-18 08:44:01 -0800 |
commit | 3164c8a70073d43629b4e11e083d3d2798f7750f (patch) | |
tree | 58e67b083df3cf3178c73f0e1ae6977786932099 /drivers/gpu/drm/bridge | |
parent | 4c8874c2a6512b9fe7285cab1a6910d9211a6cfb (diff) | |
download | linux-stable-3164c8a70073d43629b4e11e083d3d2798f7750f.tar.gz linux-stable-3164c8a70073d43629b4e11e083d3d2798f7750f.tar.bz2 linux-stable-3164c8a70073d43629b4e11e083d3d2798f7750f.zip |
drm/bridge: parade-ps8640: Never store more than msg->size bytes in AUX xfer
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.I9d1afcaad76a3e2c0ca046dc4adbc2b632c22eda@changeid
Diffstat (limited to 'drivers/gpu/drm/bridge')
-rw-r--r-- | drivers/gpu/drm/bridge/parade-ps8640.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c index 8161b1a1a4b1..d264b80d909d 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, |