Re: [PATCH -next] kernel/audit: convert comma to semicolon
On Fri, Dec 11, 2020 at 10:33 AM Richard Guy Briggs <rgb(a)redhat.com> wrote:
On 2020-12-11 16:42, Zheng Yongjun wrote:
> Replace a comma between expression statements by a semicolon.
>
> Signed-off-by: Zheng Yongjun <zhengyongjun3(a)huawei.com>
> ---
> kernel/audit.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/audit.c b/kernel/audit.c
> index 68cee3bc8cfe..c8497115be35 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -2282,7 +2282,7 @@ static void audit_log_set_loginuid(kuid_t koldloginuid, kuid_t
kloginuid,
>
> uid = from_kuid(&init_user_ns, task_uid(current));
> oldloginuid = from_kuid(&init_user_ns, koldloginuid);
> - loginuid = from_kuid(&init_user_ns, kloginuid),
> + loginuid = from_kuid(&init_user_ns, kloginuid);
Nice catch. That went unnoticed through 3 patches, the last two mine...
Yes, thanks for catching this and submitting a patch. However, as it
came very late in the v5.10-rcX release cycle I'm going to wait until
after this merge window to merge it into audit/next.
Not quite sure why no compiler complained about it...
Because it is legal; odd, but legal. :)
The comma operator allows multiple expressions to be executed with
only the last expression returned. Take the example below:
% cat test.c
#include <stdlib.h>
#include <stdio.h>
int main(int argc, char *argv[])
{
int a, b, c;
a = (b = 1, c = 2);
printf("a = %d, b = %d, c = %d\n", a, b, c);
return 0;
}
% gcc -o test test.c
% ./test
a = 2, b = 1, c = 2
... we see both "b=1" and "c=2" are executed, and the last statement
in the comma separated list of expressions is used as the right-hand
value in the "a" assignment.
In the case of this patch, the existing code is actually okay: both
expressions are executed and we don't assign either expression's value
to a variable so it doesn't matter. However, it definitely looks odd
and is something we should fix.
--
paul moore
www.paul-moore.com