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SubjectRe: [PATCH][next] cpumask: allocate enough space for string and trailing '\0' char
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On 2020-11-09 8:07 p.m., Qian Cai wrote:
> On Mon, 2020-11-09 at 13:04 +0000, Colin King wrote:
>> From: Colin Ian King <colin.king@canonical.com>
>>
>> Currently the allocation of cpulist is based on the length of buf but does
>> not include the addition end of string '\0' terminator. Static analysis is
>> reporting this as a potential out-of-bounds access on cpulist. Fix this by
>> allocating enough space for the additional '\0' terminator.
>>
>> Addresses-Coverity: ("Out-of-bounds access")
>> Fixes: 65987e67f7ff ("cpumask: add "last" alias for cpu list specifications")
>
> Yeah, this bad commit also introduced KASAN errors everywhere and then will
> disable lockdep that makes our linux-next CI miserable. Confirmed that this
> patch will fix it.

I appreciate the reports reminding me why I hate touching string handling.

But let us not lose sight of why linux-next exists. We want to
encourage code to appear there as a sounding board before it goes
mainline, so we can fix things and not pollute mainline git history
with those trivialities.

If you've decided to internalize linux-next as part of your CI, then
great, but do note that does not elevate linux-next to some pristine
status for the world at large. That only means you have to watch more
closely what is going on.

If you want to declare linux-next unbreakable -- well that would scare
away others to get the multi-arch or multi-config coverage that they may
not be able to do themselves. We are not going to do that.

I have (hopefully) fixed the "bad commit" in v2 -- as part of the
implicit linux-next rule "you broke it, you better fix it ASAP".

But "bad" and "miserable" can be things that might scare people off of
making use of linux-next for what it is meant to be for. And I am not
OK with that.

Thanks,
Paul.
--

>
>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
>> ---
>> lib/cpumask.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/lib/cpumask.c b/lib/cpumask.c
>> index 34ecb3005941..cb8a3ef0e73e 100644
>> --- a/lib/cpumask.c
>> +++ b/lib/cpumask.c
>> @@ -185,7 +185,7 @@ int __ref cpulist_parse(const char *buf, struct cpumask
>> *dstp)
>> {
>> int r;
>> char *cpulist, last_cpu[5]; /* NR_CPUS <= 9999 */
>> - size_t len = strlen(buf);
>> + size_t len = strlen(buf) + 1;
>> bool early = !slab_is_available();
>>
>> if (!strcmp(buf, "all")) {
>

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