linux-kernel - Re: [PATCH] coredump: fix cn

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Date:	Mon, 16 Mar 2015 20:23:49 +0800
From:	Nicolas Iooss <nicolas.iooss_linux@....org>
To:	viro@...iv.linux.org.uk
CC:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] coredump: fix cn_printf formatting warnings

Ping?  Comments (or NACK or ACK) would be greatly appreciated on this
patch.  Of course, if you prefer to use init_user_ns instead of
cred->user_ns, I can send an other patch.

Nicolas

On 03/06/2015 09:00 PM, Nicolas Iooss wrote:
> Add __printf attributes to cn_*printf functions.  With these, gcc says:
> 
>   fs/coredump.c:213:5: warning: format '%d' expects argument of type
>   'int', but argument 3 has type 'kuid_t' [-Wformat=]
>        err = cn_printf(cn, "%d", cred->uid);
>        ^
>   fs/coredump.c:217:5: warning: format '%d' expects argument of type
>   'int', but argument 3 has type 'kgid_t' [-Wformat=]
>        err = cn_printf(cn, "%d", cred->gid);
>        ^
>   fs/coredump.c:225:5: warning: format '%ld' expects argument of type
>   'long int', but argument 3 has type 'int' [-Wformat=]
>        err = cn_printf(cn, "%ld", cprm->siginfo->si_signo);
>        ^
> 
> The third warning is easily fixed as si_signo is always an int.
> 
> For the two others, cred->uid and cred->gid need to be converted to
> either a user-namespace UID/GID or to init_user_ns UID/GID.  As
> Documentation/sysctl/kernel.txt does not specify which user namespace is
> used to translate %u and %g in core_pattern, but lowercase %p and %i are
> used to format pid/tid in current process namespace, it seems intuitive
> that lowercase %u and %g use the current user namespace.  So implement
> this.
> 
> Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@....org>
> ---
>  fs/coredump.c | 18 ++++++++++++------
>  1 file changed, 12 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/coredump.c b/fs/coredump.c
> index f319926ddf8c..762d827825a8 100644
> --- a/fs/coredump.c
> +++ b/fs/coredump.c
> @@ -70,7 +70,8 @@ static int expand_corename(struct core_name *cn, int size)
>  	return 0;
>  }
>  
> -static int cn_vprintf(struct core_name *cn, const char *fmt, va_list arg)
> +static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
> +				     va_list arg)
>  {
>  	int free, need;
>  	va_list arg_copy;
> @@ -93,7 +94,7 @@ again:
>  	return -ENOMEM;
>  }
>  
> -static int cn_printf(struct core_name *cn, const char *fmt, ...)
> +static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
>  {
>  	va_list arg;
>  	int ret;
> @@ -105,7 +106,8 @@ static int cn_printf(struct core_name *cn, const char *fmt, ...)
>  	return ret;
>  }
>  
> -static int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
> +static __printf(2, 3)
> +int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
>  {
>  	int cur = cn->used;
>  	va_list arg;
> @@ -209,11 +211,15 @@ static int format_corename(struct core_name *cn, struct coredump_params *cprm)
>  				break;
>  			/* uid */
>  			case 'u':
> -				err = cn_printf(cn, "%d", cred->uid);
> +				err = cn_printf(cn, "%d",
> +						from_kuid_munged(cred->user_ns,
> +								 cred->uid));
>  				break;
>  			/* gid */
>  			case 'g':
> -				err = cn_printf(cn, "%d", cred->gid);
> +				err = cn_printf(cn, "%d",
> +						from_kgid_munged(cred->user_ns,
> +								 cred->gid));
>  				break;
>  			case 'd':
>  				err = cn_printf(cn, "%d",
> @@ -221,7 +227,7 @@ static int format_corename(struct core_name *cn, struct coredump_params *cprm)
>  				break;
>  			/* signal that caused the coredump */
>  			case 's':
> -				err = cn_printf(cn, "%ld", cprm->siginfo->si_signo);
> +				err = cn_printf(cn, "%d", cprm->siginfo->si_signo);
>  				break;
>  			/* UNIX time of coredump */
>  			case 't': {
> 
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