Re: Coverity: mt7915_mcu_get_chan_mib_info(): Memory - illegal accesses

Ryder Lee
2022-12-02T22:56:36Z

On Fri, 2022-12-02 at 14:24 -0800, coverity-bot wrote:
> Hello!
>
> This is an experimental semi-automated report about issues detected
> by
> Coverity from a scan of next-20221202 as part of the linux-next scan
> project:
>
https://urldefense.com/v3/__https://scan.coverity.com/projects/linux-next-weekly-scan__;!!CTRNKA9wMg0ARbw!j7j_C0KpO4VD2yMOodvpeIexTGq4fhy2yq6nokNua9u4LToiUOLk4ou8JFFNrXkrh80d5BK2k44faRQstHE9$
>
>
> You're getting this email because you were associated with the
> identified
> lines of code (noted below) that were touched by commits:
>
> Thu Feb 3 13:57:56 2022 +0100
> 417a4534d223 ("mt76: mt7915: update mt7915_chan_mib_offs for
> mt7916")
>
> Coverity reported the following:
>
> *** CID 1527801: Memory - illegal accesses (OVERRUN)
> drivers/net/wireless/mediatek/mt76/mt7915/mcu.c:3005 in
> mt7915_mcu_get_chan_mib_info()
> 2999 start = 5;
> 3000 ofs = 0;
> 3001 }
> 3002
> 3003 for (i = 0; i < 5; i++) {
> 3004 req[i].band = cpu_to_le32(phy->mt76->band_idx);
> vvv CID 1527801: Memory - illegal accesses (OVERRUN)
> vvv Overrunning array "offs" of 9 4-byte elements at element
> index 9 (byte offset 39) using index "i + start" (which evaluates to
> 9).
> 3005 req[i].offs = cpu_to_le32(offs[i + start]);
> 3006
> 3007 if (!is_mt7915(&dev->mt76) && i == 3)
> 3008 break;
> 3009 }
> 3010
>
> If this is a false positive, please let us know so we can mark it as
> such, or teach the Coverity rules to be smarter. If not, please make
> sure fixes get into linux-next. :) For patches fixing this, please
> include these lines (but double-check the "Fixes" first):
>

I think this is a false postive as the subsequent check 'if
(!is_mt7915(&dev->mt76) && i == 3)' should break array "offs" of 8.

Ryder

> Reported-by: coverity-bot <keescook+coverity-bot@chromium.org>
> Addresses-Coverity-ID: 1527801 ("Memory - illegal accesses")
> Fixes: 417a4534d223 ("mt76: mt7915: update mt7915_chan_mib_offs for
> mt7916")
>
> Thanks for your attention!
>