* [PATCH][next] ALSA: vmaster: Use flex_array_size() helper in memcpy()
@ 2020-07-29 22:18 Gustavo A. R. Silva
2020-07-30 8:41 ` Takashi Iwai
0 siblings, 1 reply; 4+ messages in thread
From: Gustavo A. R. Silva @ 2020-07-29 22:18 UTC (permalink / raw)
To: Jaroslav Kysela, Takashi Iwai
Cc: alsa-devel, linux-kernel, Gustavo A. R. Silva
Make use of the flex_array_size() helper to calculate the size of a
flexible array member within an enclosing structure.
This helper offers defense-in-depth against potential integer overflows
and makes it explicitly clear that we are dealing with a flexible array
member.
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
sound/core/vmaster.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/sound/core/vmaster.c b/sound/core/vmaster.c
index ab36f9898711..21ce4082cb5f 100644
--- a/sound/core/vmaster.c
+++ b/sound/core/vmaster.c
@@ -262,7 +262,8 @@ int _snd_ctl_add_follower(struct snd_kcontrol *master,
return -ENOMEM;
srec->kctl = follower;
srec->follower = *follower;
- memcpy(srec->follower.vd, follower->vd, follower->count * sizeof(*follower->vd));
+ memcpy(srec->follower.vd, follower->vd, flex_array_size(srec, follower.vd,
+ srec->follower.count));
srec->master = master_link;
srec->flags = flags;
--
2.27.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH][next] ALSA: vmaster: Use flex_array_size() helper in memcpy()
2020-07-29 22:18 [PATCH][next] ALSA: vmaster: Use flex_array_size() helper in memcpy() Gustavo A. R. Silva
@ 2020-07-30 8:41 ` Takashi Iwai
2020-07-30 13:12 ` Gustavo A. R. Silva
0 siblings, 1 reply; 4+ messages in thread
From: Takashi Iwai @ 2020-07-30 8:41 UTC (permalink / raw)
To: Gustavo A. R. Silva; +Cc: linux-kernel, alsa-devel, Takashi Iwai
On Thu, 30 Jul 2020 00:18:29 +0200,
Gustavo A. R. Silva wrote:
>
> Make use of the flex_array_size() helper to calculate the size of a
> flexible array member within an enclosing structure.
>
> This helper offers defense-in-depth against potential integer overflows
> and makes it explicitly clear that we are dealing with a flexible array
> member.
>
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
> sound/core/vmaster.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/sound/core/vmaster.c b/sound/core/vmaster.c
> index ab36f9898711..21ce4082cb5f 100644
> --- a/sound/core/vmaster.c
> +++ b/sound/core/vmaster.c
> @@ -262,7 +262,8 @@ int _snd_ctl_add_follower(struct snd_kcontrol *master,
> return -ENOMEM;
> srec->kctl = follower;
> srec->follower = *follower;
> - memcpy(srec->follower.vd, follower->vd, follower->count * sizeof(*follower->vd));
> + memcpy(srec->follower.vd, follower->vd, flex_array_size(srec, follower.vd,
> + srec->follower.count));
Changing from follower->count to srec->follower.count isn't obvious,
so it should have been mentioned in the log; other than that, the code
change looks good.
But since the API isn't in Linus tree yet, I'll postpone the merge
until the API reaches to upstream. Maybe I can merge this during RC1
merge window, as those are trivial.
BTW, looking at those patterns, I wonder whether it'd make sense to
make the whole memset() call as a macro like
safe_copy_array(srec->follower.vd, follower->vd, follower->count);
?
thanks,
Takashi
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH][next] ALSA: vmaster: Use flex_array_size() helper in memcpy()
2020-07-30 8:41 ` Takashi Iwai
@ 2020-07-30 13:12 ` Gustavo A. R. Silva
2020-07-30 14:57 ` Takashi Iwai
0 siblings, 1 reply; 4+ messages in thread
From: Gustavo A. R. Silva @ 2020-07-30 13:12 UTC (permalink / raw)
To: Takashi Iwai, Gustavo A. R. Silva; +Cc: linux-kernel, alsa-devel, Takashi Iwai
On 7/30/20 03:41, Takashi Iwai wrote:
> On Thu, 30 Jul 2020 00:18:29 +0200,
> Gustavo A. R. Silva wrote:
>>
>> Make use of the flex_array_size() helper to calculate the size of a
>> flexible array member within an enclosing structure.
>>
>> This helper offers defense-in-depth against potential integer overflows
>> and makes it explicitly clear that we are dealing with a flexible array
>> member.
>>
>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
>> ---
>> sound/core/vmaster.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/sound/core/vmaster.c b/sound/core/vmaster.c
>> index ab36f9898711..21ce4082cb5f 100644
>> --- a/sound/core/vmaster.c
>> +++ b/sound/core/vmaster.c
>> @@ -262,7 +262,8 @@ int _snd_ctl_add_follower(struct snd_kcontrol *master,
>> return -ENOMEM;
>> srec->kctl = follower;
>> srec->follower = *follower;
>> - memcpy(srec->follower.vd, follower->vd, follower->count * sizeof(*follower->vd));
>> + memcpy(srec->follower.vd, follower->vd, flex_array_size(srec, follower.vd,
>> + srec->follower.count));
>
> Changing from follower->count to srec->follower.count isn't obvious,
> so it should have been mentioned in the log; other than that, the code
> change looks good.
>
Yeah; you're right. I'll include that in the changelog text.
> But since the API isn't in Linus tree yet, I'll postpone the merge
> until the API reaches to upstream. Maybe I can merge this during RC1
> merge window, as those are trivial.
>
The API is already in mainline, see:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/overflow.h#n320
>
> BTW, looking at those patterns, I wonder whether it'd make sense to
> make the whole memset() call as a macro like
>
> safe_copy_array(srec->follower.vd, follower->vd, follower->count);
>
> ?
>
Yep; I was actually thinking about that, yesterday. I might implement it
for the next development cycle. :)
Thanks for the feedback.
--
Gustavo
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH][next] ALSA: vmaster: Use flex_array_size() helper in memcpy()
2020-07-30 13:12 ` Gustavo A. R. Silva
@ 2020-07-30 14:57 ` Takashi Iwai
0 siblings, 0 replies; 4+ messages in thread
From: Takashi Iwai @ 2020-07-30 14:57 UTC (permalink / raw)
To: Gustavo A. R. Silva
Cc: linux-kernel, alsa-devel, Takashi Iwai, Gustavo A. R. Silva
On Thu, 30 Jul 2020 15:12:33 +0200,
Gustavo A. R. Silva wrote:
>
>
>
> On 7/30/20 03:41, Takashi Iwai wrote:
> > On Thu, 30 Jul 2020 00:18:29 +0200,
> > Gustavo A. R. Silva wrote:
> >>
> >> Make use of the flex_array_size() helper to calculate the size of a
> >> flexible array member within an enclosing structure.
> >>
> >> This helper offers defense-in-depth against potential integer overflows
> >> and makes it explicitly clear that we are dealing with a flexible array
> >> member.
> >>
> >> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> >> ---
> >> sound/core/vmaster.c | 3 ++-
> >> 1 file changed, 2 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/sound/core/vmaster.c b/sound/core/vmaster.c
> >> index ab36f9898711..21ce4082cb5f 100644
> >> --- a/sound/core/vmaster.c
> >> +++ b/sound/core/vmaster.c
> >> @@ -262,7 +262,8 @@ int _snd_ctl_add_follower(struct snd_kcontrol *master,
> >> return -ENOMEM;
> >> srec->kctl = follower;
> >> srec->follower = *follower;
> >> - memcpy(srec->follower.vd, follower->vd, follower->count * sizeof(*follower->vd));
> >> + memcpy(srec->follower.vd, follower->vd, flex_array_size(srec, follower.vd,
> >> + srec->follower.count));
> >
> > Changing from follower->count to srec->follower.count isn't obvious,
> > so it should have been mentioned in the log; other than that, the code
> > change looks good.
> >
>
> Yeah; you're right. I'll include that in the changelog text.
OK, then I'll wait for the v2 for merging.
> > But since the API isn't in Linus tree yet, I'll postpone the merge
> > until the API reaches to upstream. Maybe I can merge this during RC1
> > merge window, as those are trivial.
> >
>
> The API is already in mainline, see:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/overflow.h#n320
Ah, thanks, I didn't expect that the API change comes after rc1 into
mainline. Then I can merge later the commits based on the late rc.
Takashi
^ permalink raw reply [flat|nested] 4+ messages in thread
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