Pkshih [off-list ref] writes:
quoted
-----Original Message-----
From: Colin King <redacted>
Sent: Friday, October 15, 2021 11:46 PM
To: Kalle Valo <redacted>; David S . Miller <davem@davemloft.net>; Jakub Kicinski
[off-list ref]; Pkshih [off-list ref]; linux-wireless@vger.kernel.org;
netdev@vger.kernel.org
Cc: kernel-janitors@vger.kernel.org; linux-kernel@vger.kernel.org
Subject: [PATCH][next] rtw89: Fix potential dereference of the null pointer sta
From: Colin Ian King <redacted>
The pointer rtwsta is dereferencing pointer sta before sta is
being null checked, so there is a potential null pointer deference
issue that may occur. Fix this by only assigning rtwsta after sta
has been null checked. Add in a null pointer check on rtwsta before
dereferencing it too.
Fixes: e3ec7017f6a2 ("rtw89: add Realtek 802.11ax driver")
Addresses-Coverity: ("Dereference before null check")
Signed-off-by: Colin Ian King <redacted>
---
drivers/net/wireless/realtek/rtw89/core.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/net/wireless/realtek/rtw89/core.c
b/drivers/net/wireless/realtek/rtw89/core.c
index 06fb6e5b1b37..26f52a25f545 100644
--- a/drivers/net/wireless/realtek/rtw89/core.c
+++ b/drivers/net/wireless/realtek/rtw89/core.c
@@ -1534,9 +1534,14 @@ static bool rtw89_core_txq_agg_wait(struct rtw89_dev *rtwdev,
{
struct rtw89_txq *rtwtxq = (struct rtw89_txq *)txq->drv_priv;
struct ieee80211_sta *sta = txq->sta;
- struct rtw89_sta *rtwsta = (struct rtw89_sta *)sta->drv_priv;
'sta->drv_priv' is only a pointer, we don't really dereference the
data right here, so I think this is safe. More, compiler can optimize
this instruction that reorder it to the place just right before using.
So, it seems like a false alarm.
quoted
+ struct rtw89_sta *rtwsta;
- if (!sta || rtwsta->max_agg_wait <= 0)
+ if (!sta)
+ return false;
+ rtwsta = (struct rtw89_sta *)sta->drv_priv;
+ if (!rtwsta)
+ return false;
+ if (rtwsta->max_agg_wait <= 0)
return false;
if (rtwdev->stats.tx_tfc_lv <= RTW89_TFC_MID)
I check the size of object files before/after this patch, and
the original one is smaller.
text data bss dec hex filename
16781 3392 1 20174 4ece core-0.o // original
16819 3392 1 20212 4ef4 core-1.o // after this patch
Do you think it is worth to apply this patch?
I think that we should apply the patch. Even though the compiler _may_
reorder the code, it might choose not to do that.
Another question is that can txq->sta really be null? I didn't check the
code, but if it should be always set when the null check is not needed.
--
https://patchwork.kernel.org/project/linux-wireless/list/
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
-----Original Message-----
From: kvalo=codeaurora.org@mg.codeaurora.org <kvalo=codeaurora.org@mg.codeaurora.org> On
Behalf Of Kalle Valo
Sent: Monday, October 18, 2021 8:12 PM
To: Pkshih <pkshih@realtek.com>
Cc: Colin King <redacted>; David S . Miller <davem@davemloft.net>; Jakub
Kicinski [off-list ref]; linux-wireless@vger.kernel.org; netdev@vger.kernel.org;
kernel-janitors@vger.kernel.org; linux-kernel@vger.kernel.org
Subject: Re: [PATCH][next] rtw89: Fix potential dereference of the null pointer sta
Pkshih [off-list ref] writes:
quoted
quoted
-----Original Message-----
From: Colin King <redacted>
Sent: Friday, October 15, 2021 11:46 PM
To: Kalle Valo <redacted>; David S . Miller <davem@davemloft.net>; Jakub Kicinski
[off-list ref]; Pkshih [off-list ref]; linux-wireless@vger.kernel.org;
netdev@vger.kernel.org
Cc: kernel-janitors@vger.kernel.org; linux-kernel@vger.kernel.org
Subject: [PATCH][next] rtw89: Fix potential dereference of the null pointer sta
From: Colin Ian King <redacted>
The pointer rtwsta is dereferencing pointer sta before sta is
being null checked, so there is a potential null pointer deference
issue that may occur. Fix this by only assigning rtwsta after sta
has been null checked. Add in a null pointer check on rtwsta before
dereferencing it too.
Fixes: e3ec7017f6a2 ("rtw89: add Realtek 802.11ax driver")
Addresses-Coverity: ("Dereference before null check")
Signed-off-by: Colin Ian King <redacted>
---
drivers/net/wireless/realtek/rtw89/core.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/net/wireless/realtek/rtw89/core.c
b/drivers/net/wireless/realtek/rtw89/core.c
index 06fb6e5b1b37..26f52a25f545 100644
--- a/drivers/net/wireless/realtek/rtw89/core.c
+++ b/drivers/net/wireless/realtek/rtw89/core.c
@@ -1534,9 +1534,14 @@ static bool rtw89_core_txq_agg_wait(struct rtw89_dev *rtwdev,
{
struct rtw89_txq *rtwtxq = (struct rtw89_txq *)txq->drv_priv;
struct ieee80211_sta *sta = txq->sta;
- struct rtw89_sta *rtwsta = (struct rtw89_sta *)sta->drv_priv;
'sta->drv_priv' is only a pointer, we don't really dereference the
data right here, so I think this is safe. More, compiler can optimize
this instruction that reorder it to the place just right before using.
So, it seems like a false alarm.
quoted
+ struct rtw89_sta *rtwsta;
- if (!sta || rtwsta->max_agg_wait <= 0)
+ if (!sta)
+ return false;
+ rtwsta = (struct rtw89_sta *)sta->drv_priv;
+ if (!rtwsta)
+ return false;
+ if (rtwsta->max_agg_wait <= 0)
return false;
if (rtwdev->stats.tx_tfc_lv <= RTW89_TFC_MID)
I check the size of object files before/after this patch, and
the original one is smaller.
text data bss dec hex filename
16781 3392 1 20174 4ece core-0.o // original
16819 3392 1 20212 4ef4 core-1.o // after this patch
Do you think it is worth to apply this patch?
I think that we should apply the patch. Even though the compiler _may_
reorder the code, it might choose not to do that.
Understand.
I have another way to fix this coverity warning, like:
@@ -1617,7 +1617,7 @@ static bool rtw89_core_txq_agg_wait(struct rtw89_dev *rtwdev,
{
struct rtw89_txq *rtwtxq = (struct rtw89_txq *)txq->drv_priv;
struct ieee80211_sta *sta = txq->sta;
- struct rtw89_sta *rtwsta = (struct rtw89_sta *)sta->drv_priv;
+ struct rtw89_sta *rtwsta = sta ? (struct rtw89_sta *)sta->drv_priv : NULL;
if (!sta || rtwsta->max_agg_wait <= 0)
return false;
Is this acceptable?
It has a little redundant checking of 'sta', but the code looks clean.
Another question is that can txq->sta really be null? I didn't check the
code, but if it should be always set when the null check is not needed.
It says
* struct ieee80211_txq - Software intermediate tx queue
* @sta: station table entry, %NULL for per-vif queue
So, we need to check if 'sta' is NULL.
--
Ping-Ke