Re: accessing ENVIRON causes SIGFPE when first var is numeric

[arnold]

Hi.

Thanks for the report.  Your fix is what I would have done; I will
get it into the code base.

As a general remark, using HEAD from masster, that is, an unreleased
version, isn't necessarily recommended.  I hope that's not what
your distribution is shipping but just what you happened to build.

Also, the use of a purely numeric value as an environment variable
name is at the least against standard practice; it might even
violate POSIX, but I gather this is what your distribution does
for you.

In any case, much thanks!

Arnold

"David Arroyo" <david@aqwari.net> wrote:

> Configuration Information [Automatically generated, do not change]:
> Machine: x86_64
> OS: linux-gnu
> Compiler: gcc
> Compilation CFLAGS: -g -O2 -DNDEBUG
> uname output: Linux dorcas 5.15.43 #1 SMP 1 x86_64 GNU/Linux
> Machine Type: x86_64-pc-linux-gnu
>
> Gawk Version: 5.1.60 (HEAD)
>
> Attestation:
>         I have read 
> https://www.gnu.org/software/gawk/manual/html_node/Bugs.html.
>         Yes
>
> Description:
>
> Since commit 7d19cbd5, if the first environment variable is a
> number, gawk will treat ENVIRON as a cint_array instead of a
> str_array. You can reproduce this with the following command
> line:
>
>       env -i \
>         $(which env) 0=foo x=bar \
>         $(which gawk) 'BEGIN { ENVIRON["x"] }' /dev/null
>
> Will yield the error:
>
>       gawk: cmd. line:1: fatal: floating point exception
>
>  at str_array.c:607 
>
> And I can see from a debugger that after the first iteration
> of load_environ, ENVIRON_node->array_funcs becomes
> cint_array_func. This issue does not occure when using
> the --posix flag.
>
> I ran into this error on my personal computer running GNU
> Guix, where the first variable in my environment is
>
>       0=/home/me/bin/startw
>
> I am not sure if this is common, as I do not see such an
> env var on a debian 10 system I had handy, and I have not
> tracked down what exactly sets that variable. But it seems
> undesirable for variations in user environment variables
> to trigger a crash.
>
> Fix:
>
> The patch below hardcodes ENVIRON_node to use the
> str_array_func family of functions. I don't know if that is
> the best way to fix the issue, but it helps to illustrate what's
> happening. I could not reproduce this issue using an 
> arbitrary array.
>
> ---
>  main.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/main.c b/main.c
> index 2cdd1e2d..3f48ddfb 100644
> --- a/main.c
> +++ b/main.c
> @@ -922,6 +922,7 @@ load_environ()
>       been_here = true;
>
>       ENVIRON_node = install_symbol(estrdup("ENVIRON", 7), Node_var_array);
> +     ENVIRON_node->array_funcs = &str_array_func;
>       for (i = 0; environ[i] != NULL; i++) {
>               static char nullstr[] = "";
>
> --
>