* [PATCH] selftests/resctrl: Fix null pointer dereference on open failed
@ 2022-04-24 21:15 Colin Ian King
2022-04-25 15:51 ` Shuah Khan
0 siblings, 1 reply; 4+ messages in thread
From: Colin Ian King @ 2022-04-24 21:15 UTC (permalink / raw)
To: Fenghua Yu, Reinette Chatre, Shuah Khan, Babu Moger,
Sai Praneeth Prakhya, linux-kselftest
Cc: kernel-janitors, linux-kernel
Currently if opening /dev/null fails to open then file pointer fp
is null and further access to fp via fprintf will cause a null
pointer dereference. Fix this by returning a negative error value
when a null fp is detected.
Fixes: a2561b12fe39 ("selftests/resctrl: Add built in benchmark")
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
---
tools/testing/selftests/resctrl/fill_buf.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/resctrl/fill_buf.c b/tools/testing/selftests/resctrl/fill_buf.c
index 51e5cf22632f..56ccbeae0638 100644
--- a/tools/testing/selftests/resctrl/fill_buf.c
+++ b/tools/testing/selftests/resctrl/fill_buf.c
@@ -121,8 +121,10 @@ static int fill_cache_read(unsigned char *start_ptr, unsigned char *end_ptr,
/* Consume read result so that reading memory is not optimized out. */
fp = fopen("/dev/null", "w");
- if (!fp)
+ if (!fp) {
perror("Unable to write to /dev/null");
+ return -1;
+ }
fprintf(fp, "Sum: %d ", ret);
fclose(fp);
--
2.35.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] selftests/resctrl: Fix null pointer dereference on open failed
2022-04-24 21:15 [PATCH] selftests/resctrl: Fix null pointer dereference on open failed Colin Ian King
@ 2022-04-25 15:51 ` Shuah Khan
2022-04-25 16:06 ` Colin King (gmail)
0 siblings, 1 reply; 4+ messages in thread
From: Shuah Khan @ 2022-04-25 15:51 UTC (permalink / raw)
To: Colin Ian King, Fenghua Yu, Reinette Chatre, Shuah Khan,
Babu Moger, Sai Praneeth Prakhya, linux-kselftest
Cc: kernel-janitors, linux-kernel, Shuah Khan
On 4/24/22 3:15 PM, Colin Ian King wrote:
> Currently if opening /dev/null fails to open then file pointer fp
> is null and further access to fp via fprintf will cause a null
> pointer dereference. Fix this by returning a negative error value
> when a null fp is detected.
>
How did you find this problem and how can it be reproduced? Is there
a case where test fails to open "/dev/null"?
> Fixes: a2561b12fe39 ("selftests/resctrl: Add built in benchmark")
> Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
> ---
> tools/testing/selftests/resctrl/fill_buf.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/resctrl/fill_buf.c b/tools/testing/selftests/resctrl/fill_buf.c
> index 51e5cf22632f..56ccbeae0638 100644
> --- a/tools/testing/selftests/resctrl/fill_buf.c
> +++ b/tools/testing/selftests/resctrl/fill_buf.c
> @@ -121,8 +121,10 @@ static int fill_cache_read(unsigned char *start_ptr, unsigned char *end_ptr,
>
> /* Consume read result so that reading memory is not optimized out. */
> fp = fopen("/dev/null", "w");
> - if (!fp)
> + if (!fp) {
> perror("Unable to write to /dev/null");
> + return -1;
> + }
> fprintf(fp, "Sum: %d ", ret);
> fclose(fp);
>
>
thanks,
-- Shuah
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] selftests/resctrl: Fix null pointer dereference on open failed
2022-04-25 15:51 ` Shuah Khan
@ 2022-04-25 16:06 ` Colin King (gmail)
2022-04-25 16:21 ` Shuah Khan
0 siblings, 1 reply; 4+ messages in thread
From: Colin King (gmail) @ 2022-04-25 16:06 UTC (permalink / raw)
To: Shuah Khan, Fenghua Yu, Reinette Chatre, Shuah Khan, Babu Moger,
Sai Praneeth Prakhya, linux-kselftest
Cc: kernel-janitors, linux-kernel
On 25/04/2022 16:51, Shuah Khan wrote:
> On 4/24/22 3:15 PM, Colin Ian King wrote:
>> Currently if opening /dev/null fails to open then file pointer fp
>> is null and further access to fp via fprintf will cause a null
>> pointer dereference. Fix this by returning a negative error value
>> when a null fp is detected.
>>
>
> How did you find this problem and how can it be reproduced? Is there
> a case where test fails to open "/dev/null"?
Found with static analysis, cppcheck. Open on /dev/null is unlikely to
fail, but it's good to fail reliably rather than have a SIGSEGV :-)
Colin
>
>> Fixes: a2561b12fe39 ("selftests/resctrl: Add built in benchmark")
>> Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
>> ---
>> tools/testing/selftests/resctrl/fill_buf.c | 4 +++-
>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/testing/selftests/resctrl/fill_buf.c
>> b/tools/testing/selftests/resctrl/fill_buf.c
>> index 51e5cf22632f..56ccbeae0638 100644
>> --- a/tools/testing/selftests/resctrl/fill_buf.c
>> +++ b/tools/testing/selftests/resctrl/fill_buf.c
>> @@ -121,8 +121,10 @@ static int fill_cache_read(unsigned char
>> *start_ptr, unsigned char *end_ptr,
>> /* Consume read result so that reading memory is not optimized
>> out. */
>> fp = fopen("/dev/null", "w");
>> - if (!fp)
>> + if (!fp) {
>> perror("Unable to write to /dev/null");
>> + return -1;
>> + }
>> fprintf(fp, "Sum: %d ", ret);
>> fclose(fp);
>>
>
> thanks,
> -- Shuah
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] selftests/resctrl: Fix null pointer dereference on open failed
2022-04-25 16:06 ` Colin King (gmail)
@ 2022-04-25 16:21 ` Shuah Khan
0 siblings, 0 replies; 4+ messages in thread
From: Shuah Khan @ 2022-04-25 16:21 UTC (permalink / raw)
To: Colin King (gmail),
Fenghua Yu, Reinette Chatre, Shuah Khan, Babu Moger,
Sai Praneeth Prakhya, linux-kselftest
Cc: kernel-janitors, linux-kernel, Shuah Khan
On 4/25/22 10:06 AM, Colin King (gmail) wrote:
> On 25/04/2022 16:51, Shuah Khan wrote:
>> On 4/24/22 3:15 PM, Colin Ian King wrote:
>>> Currently if opening /dev/null fails to open then file pointer fp
>>> is null and further access to fp via fprintf will cause a null
>>> pointer dereference. Fix this by returning a negative error value
>>> when a null fp is detected.
>>>
>>
>> How did you find this problem and how can it be reproduced? Is there
>> a case where test fails to open "/dev/null"?
>
> Found with static analysis, cppcheck. Open on /dev/null is unlikely to fail, but it's good to fail reliably rather than have a SIGSEGV :-)
>
I don't see how /dev/null open could fail here in this test.
However, I will take this fix. Please add information how
you found it and include the cppheck log in the commit log
and send me v2.
thanks,
-- Shuah
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-04-25 16:21 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2022-04-24 21:15 [PATCH] selftests/resctrl: Fix null pointer dereference on open failed Colin Ian King
2022-04-25 15:51 ` Shuah Khan
2022-04-25 16:06 ` Colin King (gmail)
2022-04-25 16:21 ` Shuah Khan
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