Re: [PATCH] usb: uas: validate status URB length before parsing the IU

[sashiko-bot@kernel.org]

> uas_stat_cmplt() dereferences iu->tag without verifying that the
> status URB actually carried a full IU header.  The transfer buffer is
> a freshly-zeroed sense_iu, so a status URB that completes
> successfully but with a short or empty actual_length — observed in
> the wild during link-level upsets (Thunderbolt-chain xhci blips) and
> on a wedging bridge — reads back as iu_id=0/tag=0 and produces the
> misleading
> 
>   stat urb: no pending cmd for uas-tag 0
> 
> log spam seen e.g. on an ASMT135x enclosure and a Samsung T7, right
> before the affected commands time out into the error handler.
> 
> Beyond the noise, a short packet that happens to carry a
> plausible-looking header could be matched to an inflight command and
> drive the state machine off garbage.  Bail out on anything shorter
> than a full struct iu.
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Olivier Kaloudoff <olivier.kaloudoff@gmail.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20261013221937.41490-1-olivier.kaloudoff@gmail.com?part=1