2018-06-20 09:52:20

by Jia-Ju Bai

Subject: [PATCH] staging: rtl8723bs: Fix two possible sleep-in-atomic-context bugs in translate_scan()

The driver may sleep with holding a spinlock.
The function call paths (from bottom to top) in Linux-4.16.7 are:

[FUNC] kzalloc(GFP_KERNEL)
drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 323:
kzalloc in translate_scan
drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 1554:
translate_scan in rtw_wx_get_scan
drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 1533:
spin_lock_bh in rtw_wx_get_scan

[FUNC] kzalloc(GFP_KERNEL)
drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 455:
kzalloc in translate_scan
drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 1554:
translate_scan in rtw_wx_get_scan
drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 1533:
spin_lock_bh in rtw_wx_get_scan

To fix these bugs, GFP_KERNEL is replaced with GFP_ATOMIC.

These bugs are found by my static analysis tool (DSAC-2) and checked by
my code review.

Signed-off-by: Jia-Ju Bai <[email protected]>
---
drivers/staging/rtl8723bs/os_dep/ioctl_linux.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/rtl8723bs/os_dep/ioctl_linux.c b/drivers/staging/rtl8723bs/os_dep/ioctl_linux.c
index b26533983864..7632b8974563 100644
--- a/drivers/staging/rtl8723bs/os_dep/ioctl_linux.c
+++ b/drivers/staging/rtl8723bs/os_dep/ioctl_linux.c
@@ -321,7 +321,7 @@ static char *translate_scan(struct adapter *padapter,
RT_TRACE(_module_rtl871x_mlme_c_, _drv_info_, ("rtw_wx_get_scan: ssid =%s\n", pnetwork->network.Ssid.Ssid));
RT_TRACE(_module_rtl871x_mlme_c_, _drv_info_, ("rtw_wx_get_scan: wpa_len =%d rsn_len =%d\n", wpa_len, rsn_len));

- buf = kzalloc(MAX_WPA_IE_LEN*2, GFP_KERNEL);
+ buf = kzalloc(MAX_WPA_IE_LEN*2, GFP_ATOMIC);
if (!buf)
return start;
if (wpa_len > 0) {
@@ -453,7 +453,7 @@ static char *translate_scan(struct adapter *padapter,
u8 *buf;
u8 *p, *pos;

- buf = kzalloc(MAX_WPA_IE_LEN, GFP_KERNEL);
+ buf = kzalloc(MAX_WPA_IE_LEN, GFP_ATOMIC);
if (!buf)
goto exit;
p = buf;
--
2.17.0

2018-06-20 09:58:28

by Dan Carpenter

Subject: Re: [PATCH] staging: rtl8723bs: Fix two possible sleep-in-atomic-context bugs in translate_scan()

On Wed, Jun 20, 2018 at 05:50:16PM +0800, Jia-Ju Bai wrote:
> The driver may sleep with holding a spinlock.
> The function call paths (from bottom to top) in Linux-4.16.7 are:
>
> [FUNC] kzalloc(GFP_KERNEL)
> drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 323:
> kzalloc in translate_scan
> drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 1554:
> translate_scan in rtw_wx_get_scan
> drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 1533:
> spin_lock_bh in rtw_wx_get_scan
>
> [FUNC] kzalloc(GFP_KERNEL)
> drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 455:
> kzalloc in translate_scan
> drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 1554:
> translate_scan in rtw_wx_get_scan
> drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 1533:
> spin_lock_bh in rtw_wx_get_scan
>
> To fix these bugs, GFP_KERNEL is replaced with GFP_ATOMIC.
>
> These bugs are found by my static analysis tool (DSAC-2) and checked by
> my code review.
>
> Signed-off-by: Jia-Ju Bai <[email protected]>
> ---
> drivers/staging/rtl8723bs/os_dep/ioctl_linux.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/staging/rtl8723bs/os_dep/ioctl_linux.c b/drivers/staging/rtl8723bs/os_dep/ioctl_linux.c
> index b26533983864..7632b8974563 100644
> --- a/drivers/staging/rtl8723bs/os_dep/ioctl_linux.c
> +++ b/drivers/staging/rtl8723bs/os_dep/ioctl_linux.c
> @@ -321,7 +321,7 @@ static char *translate_scan(struct adapter *padapter,
> RT_TRACE(_module_rtl871x_mlme_c_, _drv_info_, ("rtw_wx_get_scan: ssid =%s\n", pnetwork->network.Ssid.Ssid));
> RT_TRACE(_module_rtl871x_mlme_c_, _drv_info_, ("rtw_wx_get_scan: wpa_len =%d rsn_len =%d\n", wpa_len, rsn_len));
>
> - buf = kzalloc(MAX_WPA_IE_LEN*2, GFP_KERNEL);
> + buf = kzalloc(MAX_WPA_IE_LEN*2, GFP_ATOMIC);
> if (!buf)
> return start;

Thanks! It occurs to me that another way to detect this bug is that
one of the allocations in this function already uses GFP_ATOMIC. It
doesn't normally make sense to mix GFP_ATOMIC and GFP_KERNEL when there
isn't any locking in the function.

regards,
dan carpenter

2018-06-20 10:06:39

by Jia-Ju Bai

Subject: Re: [PATCH] staging: rtl8723bs: Fix two possible sleep-in-atomic-context bugs in translate_scan()

On 2018/6/20 17:56, Dan Carpenter wrote:
> On Wed, Jun 20, 2018 at 05:50:16PM +0800, Jia-Ju Bai wrote:
>> The driver may sleep with holding a spinlock.
>> The function call paths (from bottom to top) in Linux-4.16.7 are:
>>
>> [FUNC] kzalloc(GFP_KERNEL)
>> drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 323:
>> kzalloc in translate_scan
>> drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 1554:
>> translate_scan in rtw_wx_get_scan
>> drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 1533:
>> spin_lock_bh in rtw_wx_get_scan
>>
>> [FUNC] kzalloc(GFP_KERNEL)
>> drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 455:
>> kzalloc in translate_scan
>> drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 1554:
>> translate_scan in rtw_wx_get_scan
>> drivers/staging/rtl8723bs/os_dep/ioctl_linux.c, 1533:
>> spin_lock_bh in rtw_wx_get_scan
>>
>> To fix these bugs, GFP_KERNEL is replaced with GFP_ATOMIC.
>>
>> These bugs are found by my static analysis tool (DSAC-2) and checked by
>> my code review.
>>
>> Signed-off-by: Jia-Ju Bai <[email protected]>
>> ---
>> drivers/staging/rtl8723bs/os_dep/ioctl_linux.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/staging/rtl8723bs/os_dep/ioctl_linux.c b/drivers/staging/rtl8723bs/os_dep/ioctl_linux.c
>> index b26533983864..7632b8974563 100644
>> --- a/drivers/staging/rtl8723bs/os_dep/ioctl_linux.c
>> +++ b/drivers/staging/rtl8723bs/os_dep/ioctl_linux.c
>> @@ -321,7 +321,7 @@ static char *translate_scan(struct adapter *padapter,
>> RT_TRACE(_module_rtl871x_mlme_c_, _drv_info_, ("rtw_wx_get_scan: ssid =%s\n", pnetwork->network.Ssid.Ssid));
>> RT_TRACE(_module_rtl871x_mlme_c_, _drv_info_, ("rtw_wx_get_scan: wpa_len =%d rsn_len =%d\n", wpa_len, rsn_len));
>>
>> - buf = kzalloc(MAX_WPA_IE_LEN*2, GFP_KERNEL);
>> + buf = kzalloc(MAX_WPA_IE_LEN*2, GFP_ATOMIC);
>> if (!buf)
>> return start;
> Thanks! It occurs to me that another way to detect this bug is that
> one of the allocations in this function already uses GFP_ATOMIC. It
> doesn't normally make sense to mix GFP_ATOMIC and GFP_KERNEL when there
> isn't any locking in the function.

Yes, this pattern is interesting for bug finding :)
But to fix the bugs of this pattern, we need to decide whether
GFP_ATOMIC or GFP_KERNEL should be used here.


Best wishes,
Jia-Ju Bai

2018-06-20 10:25:18

by Dan Carpenter

Subject: Re: [PATCH] staging: rtl8723bs: Fix two possible sleep-in-atomic-context bugs in translate_scan()

On Wed, Jun 20, 2018 at 06:05:06PM +0800, Jia-Ju Bai wrote:
> > Thanks! It occurs to me that another way to detect this bug is that
> > one of the allocations in this function already uses GFP_ATOMIC. It
> > doesn't normally make sense to mix GFP_ATOMIC and GFP_KERNEL when there
> > isn't any locking in the function.
>
> Yes, this pattern is interesting for bug finding :)
> But to fix the bugs of this pattern, we need to decide whether GFP_ATOMIC or
> GFP_KERNEL should be used here.
>

Sure. But either way it's a bug. Plus this would be the first static
checker warning which warns about using GFP_ATOMIC when it's supposed to
be GFP_KERNEL. #milestone

regards,
dan carpenter