[LTP] [PATCH v16 1/2] lib: New library function tst_get_free_uid

[Wei Gao]

On Thu, Oct 22, 2026 at 05:32:49PM +0200, Petr Vorel wrote:
> > Hi Wei,
> 
> > > +uid_t tst_get_free_uid_(const char *file, const int lineno, uid_t skip);
> > > +
> > > +/**
> > > + * tst_get_free_uid() - Find a UID not assigned to any user.
> > > + * @skip: UID value to skip (pass 0 to skip none).
> > > + *
> > > + * Scans the password database for the first unused UID starting
> > > + * from 1, skipping @skip. Calls tst_brk(TBROK) if no free UID
> > > + * is found or a lookup error occurs.
> > > + *
> > > + * Return: An unused uid_t value.
> > > + */
> > > +#define tst_get_free_uid(skip) tst_get_free_uid_(__FILE__, __LINE__, (skip))
> > > +
> > >  /*
> > >   * Find unassigned gid. The skip argument can be used to ignore e.g. the main
> > >   * group of a specific user in case it's not listed in the group file. If you
> > > diff --git a/lib/tst_uid.c b/lib/tst_uid.c
> > > index b0b087362..47c267bc4 100644
> > > --- a/lib/tst_uid.c
> > > +++ b/lib/tst_uid.c
> > > @@ -5,6 +5,7 @@
> 
> > >  #include <sys/types.h>
> > >  #include <grp.h>
> > > +#include <pwd.h>
> > >  #include <errno.h>
> 
> > >  #define TST_NO_DEFAULT_MAIN
> > > @@ -12,6 +13,33 @@
> > >  #include "tst_uid.h"
> 
> > >  #define MAX_GID 32767
> > > +#define MAX_UID 32767
> > > +
> > > +uid_t tst_get_free_uid_(const char *file, const int lineno, uid_t skip)
> > > +{
> > > +	uid_t ret;
> > > +
> > > +	for (ret = 1; ret < MAX_UID; ret++) {
> > > +		if (ret == skip)
> > > +			continue;
> > > +
> > > +		errno = 0;
> > > +		if (getpwuid(ret))
> > > +			continue;
> 
> 
> > If you don't mind I'd prefer to use the same approach which is on
> > tst_get_free_gid_(), e.g. set errno first:
> 
> > 	errno = 0;
> 
> > 	for (ret = 1; ret < MAX_UID; ret++) {
> > 		if (ret == skip || getpwuid(ret))
> > 			continue;
> 
> > Reviewed-by: Petr Vorel <pvorel@suse.cz>
> 
> > Other than that LGTM.
> 
> > Cc Martin in case he wants to add his ack before I merge.
> 
> > Kind regards,
> > Petr
> 
> > > +
> > > +		if (errno == 0 || errno == ENOENT || errno == ESRCH) {
> > > +			tst_res_(file, lineno, TINFO,
> Actually also here TERRNO probably makes sense.
> 
> I suggest to merge with following diff:
Thanks. That's ok for me, will use your suggest on next patch once Martin give feedback.
> 
> +++ lib/tst_uid.c
> @@ -19,16 +19,14 @@ uid_t tst_get_free_uid_(const char *file, const int lineno, uid_t skip)
>  {
>  	uid_t ret;
>  
> -	for (ret = 1; ret < MAX_UID; ret++) {
> -		if (ret == skip)
> -			continue;
> +	errno = 0;
>  
> -		errno = 0;
> -		if (getpwuid(ret))
> +	for (ret = 1; ret < MAX_UID; ret++) {
> +		if (ret == skip || getpwuid(ret))
>  			continue;
>  
>  		if (errno == 0 || errno == ENOENT || errno == ESRCH) {
> -			tst_res_(file, lineno, TINFO,
> +			tst_res_(file, lineno, TINFO | TERRNO,
>  				"Found unused UID %d", (int)ret);
>  			return ret;
>  		}