RE: [PATCH v3] rtlwifi: rtl8821ae: Fix global-out-of-bounds bug in _rtl8812ae_phy_set_txpower_limit()

[Ping-Ke Shih <pkshih@realtek.com>]

> -----Original Message-----
> From: Li Zetao <lizetao1@huawei.com>
> Sent: Monday, December 12, 2022 10:36 AM
> To: Ping-Ke Shih <pkshih@realtek.com>
> Cc: Larry.Finger@lwfinger.net; davem@davemloft.net; edumazet@google.com; kuba@kernel.org;
> kvalo@kernel.org; linux-kernel@vger.kernel.org; linux-wireless@vger.kernel.org; linville@tuxdriver.com;
> lizetao1@huawei.com; netdev@vger.kernel.org; pabeni@redhat.com
> Subject: [PATCH v3] rtlwifi: rtl8821ae: Fix global-out-of-bounds bug in _rtl8812ae_phy_set_txpower_limit()
> 
> There is a global-out-of-bounds reported by KASAN:
> 
>   BUG: KASAN: global-out-of-bounds in
>   _rtl8812ae_eq_n_byte.part.0+0x3d/0x84 [rtl8821ae]
>   Read of size 1 at addr ffffffffa0773c43 by task NetworkManager/411
> 
>   CPU: 6 PID: 411 Comm: NetworkManager Tainted: G      D
>   6.1.0-rc8+ #144 e15588508517267d37
>   Hardware name: QEMU Standard PC (Q35 + ICH9, 2009),
>   Call Trace:
>    <TASK>
>    ...
>    kasan_report+0xbb/0x1c0
>    _rtl8812ae_eq_n_byte.part.0+0x3d/0x84 [rtl8821ae]
>    rtl8821ae_phy_bb_config.cold+0x346/0x641 [rtl8821ae]
>    rtl8821ae_hw_init+0x1f5e/0x79b0 [rtl8821ae]
>    ...
>    </TASK>
> 
> The root cause of the problem is that the comparison order of
> "prate_section" in _rtl8812ae_phy_set_txpower_limit() is wrong. The
> _rtl8812ae_eq_n_byte() is used to compare the first n bytes of the two
> strings from tail to head, which causes the problem. In the
> _rtl8812ae_phy_set_txpower_limit(), it was originally intended to meet
> this requirement by carefully designing the comparison order.
> For example, "pregulation" and "pbandwidth" are compared in order of
> length from small to large, first is 3 and last is 4. However, the
> comparison order of "prate_section" dose not obey such order requirement,
> therefore when "prate_section" is "HT", when comparing from tail to head,
> it will lead to access out of bounds in _rtl8812ae_eq_n_byte(). As
> mentioned above, the _rtl8812ae_eq_n_byte() has the same function as
> strcmp(), so just strcmp() is enough.
> 
> Fix it by removing _rtl8812ae_eq_n_byte() and use strcmp() barely.
> Although it can be fixed by adjusting the comparison order of
> "prate_section", this may cause the value of "rate_section" to not be
> from 0 to 5. In addition, commit "21e4b0726dc6" not only moved driver
> from staging to regular tree, but also added setting txpower limit
> function during the driver config phase, so the problem was introduced
> by this commit.
> 
> Fixes: 21e4b0726dc6 ("rtlwifi: rtl8821ae: Move driver from staging to regular tree")
> Signed-off-by: Li Zetao <lizetao1@huawei.com>

Thanks for your fix.

Acked-by: Ping-Ke Shih <pkshih@realtek.com>

> ---
> v1 -> v2: delete the third parameter of _rtl8812ae_eq_n_byte() and use
> strcmp to replace loop comparison.
> v2 -> v3: remove _rtl8812ae_eq_n_byte() and use strcmp() barely.
> 
>  .../wireless/realtek/rtlwifi/rtl8821ae/phy.c  | 52 +++++++------------
>  1 file changed, 20 insertions(+), 32 deletions(-)
> 

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