Re: automount core's on strdup(NULL)

[Ian Kent <raven@themaw.net>]

Marty Leisner wrote:
> I just installed opensuse 11.1 -- couldn't get autofs to work...
> 
> I scratched my head - its using 5.03 --so I got 5.04 -- also core (but 
> I could build it -g).
> 
> So I got the head of the git tree....same problem...
> 
> (gdb) bt
>  #0  0xb7f37743 in strlen () from /lib/libc.so.6
>  #1  0xb7f37465 in strdup () from /lib/libc.so.6
>  #2  0xb80abaf5 in master_new_mapent (master=0xb80c4368, path=0x0,
>      age=1239478044) at master.c:666
>  #3  0xb80b18ab in master_parse_entry (buffer=0xb80e0aa0 "/net /etc/auto.net",
>      default_timeout=600, logging=0, age=1239478044) at master_parse.y:771

But buffer is a valid map entry in this case.

If path ends up as NULL after parsing a valid map entry then we would be
seeing a lot more problems.

So what exactly were the circumstances that lead to this?

>  #4  0xb7eab462 in lookup_read_master (master=0xb80c4368, age=1239478044,
>      context=0xb80c5430) at lookup_file.c:469
>  #5  0xb809b744 in do_read_master (master=0xb80c4368, type=0xb80c4458 "files",
>      age=1239478044) at lookup.c:96
>  #6  0xb809b8a9 in read_master_map (master=0xb80c4368, type=0xb80c4458 "files",
>      age=1239478044) at lookup.c:135
>  #7  0xb809bc80 in lookup_nss_read_master (master=0xb80c4368, age=1239478044)
>      at lookup.c:223
>  #8  0xb80ac1cb in master_read_master (master=0xb80c4368, age=1239478044,
>      readall=0) at master.c:814
>  #9  0xb8091e2c in main (argc=0, argv=0xbfcbde40) at automount.c:2094
> 
> I ended up doing this:
> : leisner@gateway 03:42:23;rcsdiff -u master.c
> ===================================================================
> RCS file: master.c,v
> retrieving revision 1.1
> diff -u -r1.1 master.c
> --- master.c    2009/04/11 19:35:35     1.1
> +++ master.c    2009/04/11 19:36:20
> @@ -657,6 +657,9 @@
>         int status;
>         char *tmp;
> 
> +       if(!path)
> +               return NULL;
> +
>         entry = malloc(sizeof(struct master_mapent));
>         if (!entry)
>                 return NULL;
> 
> I think I ended up with a parse error at the end (not sure that was valid
> when I started -- I had
> misc  /etc/auto.misc

If that was the case the master map parser should have caught this as it
requires a "/" to even get started otherwise it returns a parse error.

We haven't got to the bottom of what caused the problem you saw and
putting in the check you have above is just going to hide the actual
problem so it can return to haunt us later.

Ian


Ian