Re: [PATCH v3] ifaddrs: Get rid of alloca

[Jeff Law <jeffreyalaw@gmail.com>]

On 5/30/23 09:25, Joe Simmons-Talbott via Libc-alpha wrote:
> Use scratch_buffer and malloc rather than alloca to avoid potential stack
> overflows.
> ---
> Changes to v2:
>    * Initialize the scratch_buffer earlier to avoid memory access errors
>      when calling scratch_buffer_free for failure cases.
> 
> Changes to v1:
>    * in __netlink_request use an 8kb buffer size and malloc rather than a
>      scratch_buffer.
> 
>      Suggested-by: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
[ ... ]
Just wanted to say thanks for doing this.  alloca has been a nightmare 
through the years from a security standpoint.

I advocated for its removal from glibc years ago based on the simple 
fact that the bugs exposed by the "bad guys" showed that even 
experienced developers are prone to get this stuff wrong.

Instead I wanted to have GCC prove particular allocations were safe to 
transform into alloca.  That never panned out, but I still think the 
compiler is the right place to exploit the performance improvements one 
gets from alloca vs malloc/free.

jeff