netdev - [BUG] iwlegacy: 3945-rs: possible null-pointer dereference in il3945_rs_get

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Message-ID: <c9663714-a352-7c5c-1826-c7a1cd6d9abf@gmail.com>
Date:   Sat, 31 Jul 2021 11:39:53 +0800
From:   Li Tuo <islituo@...il.com>
To:     stf_xl@...pl, kvalo@...eaurora.org, davem@...emloft.net,
        kuba@...nel.org
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, baijiaju1990@...il.com
Subject: [BUG] iwlegacy: 3945-rs: possible null-pointer dereference in
 il3945_rs_get_rate()

Hello,

Our static analysis tool finds a possible null-pointer dereference in 
the iwlegacy driver in Linux 5.14.0-rc3:

The variable rs_sta is checked in:
629:    if (rs_sta && !rs_sta->il)

This indicates that rs_sta can be NULL.
If so, some null-pointer dereferences will occur in some statements such as:
643:    idx = min(rs_sta->last_txrate_idx & 0xffff, RATE_COUNT_3945 - 1);
653:    if (rs_sta->start_rate != RATE_INVALID)

I am not quite sure whether this possible null-pointer dereference is 
real and how to fix it if it is real.
Any feedback would be appreciated, thanks!

Reported-by: TOTE Robot <oslab@...nghua.edu.cn>

Best wishes,
Tuo Li