Re: [PATCH] fix getgrouplist without nscd

[Rich Felker <dalias@libc.org>]

On Tue, Jul 12, 2016 at 11:30:57AM +0200, Joakim Sindholt wrote:
> There were two issues here. First, if socket() fails then it's
> treated as an unrecoverable error and second: the response buffer
> was not initialized and so a recoverable error (ie. no nscd) would
> result in UB.
> 
> dgp tested this patch and confirmed on IRC that it worked in the
> no-nscd no-socket case and I have tested it in the has-nscd case.

> >From 9251aff794832e0e37f5b747b69e756ac836f181 Mon Sep 17 00:00:00 2001
> From: Joakim Sindholt <opensource@zhasha.com>
> Date: Tue, 12 Jul 2016 10:13:23 +0200
> Subject: [PATCH] fix getgrouplist without nscd
> 
> ---
>  src/passwd/getgrouplist.c | 2 +-
>  src/passwd/nscd_query.c   | 8 +++++++-
>  2 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/src/passwd/getgrouplist.c b/src/passwd/getgrouplist.c
> index 43e5182..fd0bf5f 100644
> --- a/src/passwd/getgrouplist.c
> +++ b/src/passwd/getgrouplist.c
> @@ -17,7 +17,7 @@ int getgrouplist(const char *user, gid_t gid, gid_t *groups, int *ngroups)
>  	struct group *res;
>  	FILE *f;
>  	int swap = 0;
> -	int32_t resp[INITGR_LEN];
> +	int32_t resp[INITGR_LEN] = {0};
>  	uint32_t *nscdbuf = 0;
>  	char *buf = 0;
>  	char **mem = 0;
> diff --git a/src/passwd/nscd_query.c b/src/passwd/nscd_query.c
> index d38e371..8641e4f 100644
> --- a/src/passwd/nscd_query.c
> +++ b/src/passwd/nscd_query.c
> @@ -40,7 +40,13 @@ retry:
>  	buf[0] = NSCDVERSION;
>  
>  	fd = socket(PF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
> -	if (fd < 0) return NULL;
> +	if (fd < 0) {
> +		if (errno == EACCES || errno == EAFNOSUPPORT || errno == EPROTONOSUPPORT) {
> +			errno = errno_save;
> +			return fopen("/dev/null", "re");
> +		}
> +		return 0;
> +	}
>  
>  	if(!(f = fdopen(fd, "r"))) {
>  		close(fd);
> -- 
> 2.7.3
> 

I just ran across this patch that got lost last year while looking at
the git history for src/passwd and seeing commit
39494a273eaa6b714e0fa0c59ce7a1f5fbc80a1e. Was there any further
progress or discussion on it I might be overlooking? I think the
concept looks right but I wonder if there's a good way to avoid the
spurious /dev/null access.

Rich