linux-kernel - Re: [PATCH v10 8/9] kselftest: save-and-restore errno to allow for %m formatting

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Date:   Fri, 19 Jul 2019 16:25:46 -0600
From:   shuah <shuah@...nel.org>
To:     Aleksa Sarai <cyphar@...har.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Jeff Layton <jlayton@...nel.org>,
        "J. Bruce Fields" <bfields@...ldses.org>,
        Arnd Bergmann <arnd@...db.de>,
        David Howells <dhowells@...hat.com>,
        Shuah Khan <skhan@...uxfoundation.org>
Cc:     Eric Biederman <ebiederm@...ssion.com>,
        Andy Lutomirski <luto@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Jann Horn <jannh@...gle.com>,
        Christian Brauner <christian@...uner.io>,
        Tycho Andersen <tycho@...ho.ws>,
        David Drysdale <drysdale@...gle.com>,
        Chanho Min <chanho.min@....com>,
        Oleg Nesterov <oleg@...hat.com>, Aleksa Sarai <asarai@...e.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        containers@...ts.linux-foundation.org, linux-alpha@...r.kernel.org,
        linux-api@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-ia64@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-m68k@...ts.linux-m68k.org, linux-mips@...r.kernel.org,
        linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
        linux-xtensa@...ux-xtensa.org, sparclinux@...r.kernel.org,
        shuah <shuah@...nel.org>
Subject: Re: [PATCH v10 8/9] kselftest: save-and-restore errno to allow for %m
 formatting

On 7/19/19 10:42 AM, Aleksa Sarai wrote:
> Previously, using "%m" in a ksft_* format string can result in strange
> output because the errno value wasn't saved before calling other libc
> functions. The solution is to simply save and restore the errno before
> we format the user-supplied format string.
> 
> Signed-off-by: Aleksa Sarai <cyphar@...har.com>
> ---
>   tools/testing/selftests/kselftest.h | 15 +++++++++++++++
>   1 file changed, 15 insertions(+)
> 
> diff --git a/tools/testing/selftests/kselftest.h b/tools/testing/selftests/kselftest.h
> index ec15c4f6af55..0ac49d91a260 100644
> --- a/tools/testing/selftests/kselftest.h
> +++ b/tools/testing/selftests/kselftest.h
> @@ -10,6 +10,7 @@
>   #ifndef __KSELFTEST_H
>   #define __KSELFTEST_H
>   
> +#include <errno.h>
>   #include <stdlib.h>
>   #include <unistd.h>
>   #include <stdarg.h>
> @@ -81,58 +82,68 @@ static inline void ksft_print_cnts(void)
>   
>   static inline void ksft_print_msg(const char *msg, ...)
>   {
> +	int saved_errno = errno;
>   	va_list args;
>   
>   	va_start(args, msg);
>   	printf("# ");
> +	errno = saved_errno;
>   	vprintf(msg, args);
>   	va_end(args);
>   }
>   
>   static inline void ksft_test_result_pass(const char *msg, ...)
>   {
> +	int saved_errno = errno;
>   	va_list args;
>   
>   	ksft_cnt.ksft_pass++;
>   
>   	va_start(args, msg);
>   	printf("ok %d ", ksft_test_num());
> +	errno = saved_errno;
>   	vprintf(msg, args);
>   	va_end(args);
>   }
>   
>   static inline void ksft_test_result_fail(const char *msg, ...)
>   {
> +	int saved_errno = errno;
>   	va_list args;
>   
>   	ksft_cnt.ksft_fail++;
>   
>   	va_start(args, msg);
>   	printf("not ok %d ", ksft_test_num());
> +	errno = saved_errno;
>   	vprintf(msg, args);
>   	va_end(args);
>   }
>   
>   static inline void ksft_test_result_skip(const char *msg, ...)
>   {
> +	int saved_errno = errno;
>   	va_list args;
>   
>   	ksft_cnt.ksft_xskip++;
>   
>   	va_start(args, msg);
>   	printf("not ok %d # SKIP ", ksft_test_num());
> +	errno = saved_errno;
>   	vprintf(msg, args);
>   	va_end(args);
>   }
>   
>   static inline void ksft_test_result_error(const char *msg, ...)
>   {
> +	int saved_errno = errno;
>   	va_list args;
>   
>   	ksft_cnt.ksft_error++;
>   
>   	va_start(args, msg);
>   	printf("not ok %d # error ", ksft_test_num());
> +	errno = saved_errno;
>   	vprintf(msg, args);
>   	va_end(args);
>   }
> @@ -152,10 +163,12 @@ static inline int ksft_exit_fail(void)
>   
>   static inline int ksft_exit_fail_msg(const char *msg, ...)
>   {
> +	int saved_errno = errno;
>   	va_list args;
>   
>   	va_start(args, msg);
>   	printf("Bail out! ");
> +	errno = saved_errno;
>   	vprintf(msg, args);
>   	va_end(args);
>   
> @@ -178,10 +191,12 @@ static inline int ksft_exit_xpass(void)
>   static inline int ksft_exit_skip(const char *msg, ...)
>   {
>   	if (msg) {
> +		int saved_errno = errno;
>   		va_list args;
>   
>   		va_start(args, msg);
>   		printf("not ok %d # SKIP ", 1 + ksft_test_num());
> +		errno = saved_errno;
>   		vprintf(msg, args);
>   		va_end(args);
>   	} else {
> 

Hi Aleksa,

Can you send this patch separate from the patch series. I will apply
this as bug fix to 5.3-rc2 or rc3.

This isn't part of this series anyway and I would like to get this in
right away.

thanks,
-- Shuah