Re: [PATCH] nscd: Drop local address tuple variable [BZ #29607]

["Holger Hoffstätte" <holger@applied-asynchrony.com>]

On 2022-10-04 02:06, Siddhesh Poyarekar wrote:
> When a request needs to be resent (e.g. due to insufficient buffer
> space), the references to subsequent tuples in the local variable are
> stale and should not be used.  This used to work by accident before, but
> since 1d495912a it no longer does.  Instead of trying to reset it, just
> let gethostbyname4_r write into TUMPBUF6 for us, thus maintaining a
> consistent state at all times.  This is now consistent with what is done
> in gaih_inet for getaddrinfo.
> 
> Resolves: BZ #29607
> Reported-by: Holger Hoffstätte <holger@applied-asynchrony.com>
> ---
> 
> Tested on x86_64 with Fedora and nscd enabled.  Testing with other
> distributions would be really appreciated!
> 
> Thanks,
> Sid
> 
> 
>   nscd/aicache.c | 5 ++---
>   1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/nscd/aicache.c b/nscd/aicache.c
> index 51e793199f..e0baed170b 100644
> --- a/nscd/aicache.c
> +++ b/nscd/aicache.c
> @@ -110,11 +110,10 @@ addhstaiX (struct database_dyn *db, int fd, request_header *req,
>   							  "gethostbyname4_r");
>         if (fct4 != NULL)
>   	{
> -	  struct gaih_addrtuple atmem;
>   	  struct gaih_addrtuple *at;
>   	  while (1)
>   	    {
> -	      at = &atmem;
> +	      at = NULL;
>   	      rc6 = 0;
>   	      herrno = 0;
>   	      status[1] = DL_CALL_FCT (fct4, (key, &at,
> @@ -137,7 +136,7 @@ addhstaiX (struct database_dyn *db, int fd, request_header *req,
>   	    goto next_nip;
>   
>   	  /* We found the data.  Count the addresses and the size.  */
> -	  for (const struct gaih_addrtuple *at2 = at = &atmem; at2 != NULL;
> +	  for (const struct gaih_addrtuple *at2 = at; at2 != NULL;
>   	       at2 = at2->next)
>   	    {
>   	      ++naddrs;
> 

Hello Siddesh,

I am happy to report that this seems to be working fine and fixes the reported bug;
there haven't been any nscd crashes for a few hours now on any of my machines.
Thanks!

Holger