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Subject: Re: [PATCH 2/2] libselinux: procattr: return einval for <= 0 pid args.
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From: Daniel Cashman <dcashman@android.com>
Message-ID: <56CCC13F.3060709@android.com>
Date: Tue, 23 Feb 2016 12:29:51 -0800
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On 02/23/2016 12:24 PM, Daniel Cashman wrote:
> From: dcashman <dcashman@android.com>
> 
> getpidcon documentation does not specify that a pid of 0 refers to the
> current process, and getcon exists specifically to provide this
> functionality, and getpidcon(getpid()) would provide it as well.
> Disallow pid values <= 0 that may lead to unintended behavior in
> userspace object managers.
> 
> Signed-off-by: Daniel Cashman <dcashman@android.com>
> ---
>  libselinux/src/procattr.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/libselinux/src/procattr.c b/libselinux/src/procattr.c
> index c20f003..eee4612 100644
> --- a/libselinux/src/procattr.c
> +++ b/libselinux/src/procattr.c
> @@ -306,11 +306,21 @@ static int setprocattrcon(const char * context,
>  #define getpidattr_def(fn, attr) \
>  	int get##fn##_raw(pid_t pid, char **c)	\
>  	{ \
> -		return getprocattrcon_raw(c, pid, #attr); \
> +		if (pid <= 0) { \
> +			errno = EINVAL; \
> +			return -1; \
> +		} else { \
> +			return getprocattrcon_raw(c, pid, #attr); \
> +		} \
>  	} \
>  	int get##fn(pid_t pid, char **c)	\
>  	{ \
> -		return getprocattrcon(c, pid, #attr); \
> +		if (pid <= 0) { \
> +			errno = EINVAL; \
> +			return -1; \
> +		} else { \
> +			return getprocattrcon(c, pid, #attr); \
> +		} \
>  	}
>  
>  all_selfattr_def(con, current)
> 

I need to point out explicitly that this change would, of course, break
the existing ABI and result in a change in behavior for applications
relying on getpidcon(0,) calls to be the same as getcon().

Thanks,
Dan