Hi Ping-Ke,
On 2022/12/10 21:15, Ping-Ke Shih wrote:
On Sat, 2022-12-10 at 20:47 +0800, Li Zetao wrote:
Hi Ping-Ke,
On 2022/12/9 13:11, Ping-Ke Shih wrote:
-----Original Message-----
From: Li Zetao <lizetao1@xxxxxxxxxx>
Sent: Wednesday, December 7, 2022 11:23 PM
To: Ping-Ke Shih <pkshih@xxxxxxxxxxx>; kvalo@xxxxxxxxxx; davem@xxxxxxxxxxxxx;
edumazet@xxxxxxxxxx;
kuba@xxxxxxxxxx; pabeni@xxxxxxxxxx
Cc: lizetao1@xxxxxxxxxx; Larry.Finger@xxxxxxxxxxxx; linville@xxxxxxxxxxxxx;
linux-wireless@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
Subject: [PATCH] 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, so this requires the length of the two strings be greater
than or equal to n. 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", it will
lead to access out of bounds in _rtl8812ae_eq_n_byte().
Fix it by adding a length check in _rtl8812ae_eq_n_byte(). 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@xxxxxxxxxx>
---
drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c
b/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c
index a29321e2fa72..720114a9ddb2 100644
--- a/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c
+++ b/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c
@@ -1600,7 +1600,7 @@ static bool _rtl8812ae_get_integer_from_string(const char *str, u8
*pint)
static bool _rtl8812ae_eq_n_byte(const char *str1, const char *str2, u32 num)
{
This can causes problem because it compares characters from tail to head, and
we can't simply replace this by strncmp() that does similar work. But, I also
don't like strlen() to loop 'str1' constantly.
How about having a simple loop to compare characters forward:
for (i = 0; i < num; i++)
if (str1[i] != str2[i])
return false;
return true;
Thanks for your comment, but I don't think the problem has anything to
do with head-to-tail or
tail-to-head comparison. The problem is that num is the length of str2,
but the length of str1 may
be less than num, which may lead to reading str1 out of bounds, for
example, when comparing
"prate_section", str1 may be "HT", while str2 may by "CCK", and num is
3. So I think it is neccssary
to check the length of str1 to ensure that will not read out of bounds.
I know your point, and I believe your patch can work well, but I would like
to have simple code that can solve this specific problem.
Since both str1 and str2 are null-terminator strings, so str1[2]='\0' is
accessible if str1="HT", right? Then, if length of str1 and str2 is
different, null-terminator can help to break head-to-tail loop.
Take "12" and "1234" as an example:
Then, num=4,
head-to-tail tail-to-head
------------------- -------------------------------------------------
str1[0] == str2[0] str1[3] >< str2[3] (str1[3] is inaccessible)
str1[1] == str2[1]
str1[2] != str2[2]
I hope this can help to explain my point.
Thank you, I get your point now.
After I think deeper, it seems like third parameter 'u32 num' isn't necessary,
and then just strcmp(str1, str2) is enough.
Ping-Ke
I will replace _rtl8812ae_eq_n_byte with strcmp in the v2 and do a full
test.
With Best Regards,
Li Zetao
