[giflib-devel] Hardening giflib's memory allocation

Dear giflib developers,

I've started working on initial hardening of the memory allocation for giflib.

I imported OpenBSD's reallocarray() which has useful check for overflows:

Please see:

https://github.com/AstrodogInc/secfu/blob/master/giflib/giflib.patch

>From OpenBSD's man page:
The above test is not sufficient in all cases. For example,
multiplying ints requires a different set of checks:

int num, size;
...

/* Avoid invalid requests */
if (size < 0 || num < 0)
errc(1, EOVERFLOW, "overflow");

/* Check for signed int overflow */
if (size && num > INT_MAX / size)
errc(1, EOVERFLOW, "overflow");

if ((p = malloc(size * num)) == NULL)
err(1, "malloc");

Assuming the implementation checks for integer overflow as OpenBSD
does, it is much easier to use calloc() or reallocarray().
The above examples could be simplified to:

if ((p = reallocarray(NULL, num, size)) == NULL)
err(1, "reallocarray");

I have converted 2 calls to reallocarray() (Thanks to
bc...@op... for reviewing my diff).

I can start looking at other areas that will benefit from
reallocarray(), if there is interest upstream-wise.

Are you guys interested in this ?


Kind regards,
//Logan
C-x-C-c


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