NSS modules and errno if key not found

NSS modules and errno if key not found

[Thorsten Kukuk]

Hi,

I found a problem today when debugging some NSS releated problems.

If somebody calls getgrnam_r (or any other reentrant NSS function),
the return value of the function will be errno if the status is not
NSS_STATUS_SUCCESS.

But in the case of NSS_STATUS_NOTFOUND, no NSS module sets errno,
so the return value is a random value, but should be zero.

Who should set errno in this case? Should all NSS modules set
errno? Or should we explicit return 0 in the getXXbyYY_r functions
for NSS_STATUS_NOTFOUND?

Testcase:

#include <grp.h>
#include <errno.h>

int main ()
{
   char buffer[8048];
   struct group *result = (void *)12, gbuf;

   errno = 211;

   int ret = getgrnam_r ("notexistent", &gbuf, buffer, sizeof (buffer),
                         &result);

   printf ("errno=%d, ret=%d, result=%p\n", errno, ret, result);

   return 0;
}


-- 
Thorsten Kukuk       http://www.suse.de/~kukuk/        kukuk@suse.de
SuSE Linux AG        Maxfeldstr. 5                 D-90409 Nuernberg
--------------------------------------------------------------------    
Key fingerprint = A368 676B 5E1B 3E46 CFCE  2D97 F8FD 4E23 56C6 FB4B

Re: NSS modules and errno if key not found

[Thorsten Kukuk]

On Fri, Mar 26, Thorsten Kukuk wrote:

> 
> Hi,
> 
> I found a problem today when debugging some NSS releated problems.
> 
> If somebody calls getgrnam_r (or any other reentrant NSS function),
> the return value of the function will be errno if the status is not
> NSS_STATUS_SUCCESS.
> 
> But in the case of NSS_STATUS_NOTFOUND, no NSS module sets errno,
> so the return value is a random value, but should be zero.
> 
> Who should set errno in this case? Should all NSS modules set
> errno? Or should we explicit return 0 in the getXXbyYY_r functions
> for NSS_STATUS_NOTFOUND?

Looking at getXXbyYY_r.c, we can only change it in this file.
My proposed fix:

2004-03-27  Thorsten Kukuk  <kukuk@suse.de>

	* nss/getXXbyYY_r.c: If key is not found, return zero, not
	a random errno value.

--- nss/getXXbyYY_r.c	10 Mar 2004 09:28:25 -0000	1.57
+++ nss/getXXbyYY_r.c	27 Mar 2004 08:44:52 -0000
@@ -256,6 +256,11 @@
   else if (status == NSS_STATUS_TRYAGAIN && *h_errnop != NETDB_INTERNAL)
     res = EAGAIN;
 #endif
+  else if (status == NSS_STATUS_NOTFOUND)
+    {
+      __set_errno (ENOENT);
+      return 0;
+    }
   else
     return errno;
 

-- 
Thorsten Kukuk       http://www.suse.de/~kukuk/        kukuk@suse.de
SuSE Linux AG        Maxfeldstr. 5                 D-90409 Nuernberg
--------------------------------------------------------------------    
Key fingerprint = A368 676B 5E1B 3E46 CFCE  2D97 F8FD 4E23 56C6 FB4B

Re: NSS modules and errno if key not found

[Ulrich Drepper]

Thorsten Kukuk wrote:

> 	* nss/getXXbyYY_r.c: If key is not found, return zero, not
> 	a random errno value.
> 
> --- nss/getXXbyYY_r.c	10 Mar 2004 09:28:25 -0000	1.57
> +++ nss/getXXbyYY_r.c	27 Mar 2004 08:44:52 -0000
> @@ -256,6 +256,11 @@
>    else if (status == NSS_STATUS_TRYAGAIN && *h_errnop != NETDB_INTERNAL)
>      res = EAGAIN;
>  #endif
> +  else if (status == NSS_STATUS_NOTFOUND)
> +    {
> +      __set_errno (ENOENT);
> +      return 0;
> +    }

That's not really necessary, errno need not be set.  But since we always
do it for some compatibility reason it is OK.  But your patch is not
optimal, take a look at the change I've checked in.

-- 
➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖