Seems useful to me
Sent from my iPhone
> On Oct 7, 2017, at 13:29, Andrew Cagney <andrew.cag...@gmail.com> wrote:
>
> I'm considering a commit containing some of the below additional checks:
>
> - try to spot a double free (I think this check should go in)
>
> - try to spot a use-after-free, not so sure about this
>
> - and there is also the possibility of a check for heap overflow
>
> but these start to stray into checks that free() is doing anyway :-/
>
> thoughts,
> Andrew
>
> diff --git a/lib/libswan/alloc.c b/lib/libswan/alloc.c
> index ab6f3194b..c1f9824e7 100644
> --- a/lib/libswan/alloc.c
> +++ b/lib/libswan/alloc.c
> @@ -61,6 +61,20 @@ void set_alloc_exit_log_func(exit_log_func_t func)
> /* this magic number is 3671129837 decimal (623837458 complemented) */
> #define LEAK_MAGIC 0xDAD0FEEDul
>
> +#define INVALID_MAGIC 0xFE
> +#if __SIZEOF_POINTER__ == 4
> +#define INVALID_POINTER ((void*)0xFEFEFEFEul)
> +#endif
> +#if __SIZEOF_POINTER__ == 8
> +#define INVALID_POINTER ((void*)0xFEFEFEFEFEFEFEFEull)
> +#endif
> +#ifndef INVALID_POINTER
> +/* suppresses check */
> +#define INVALID_POINTER NULL
> +#endif
> +
> +static bool check_invalid_pointer = true;
> +
> union mhdr {
> struct {
> const char *name;
> @@ -116,6 +130,9 @@ static void *alloc_bytes_raw(size_t size, const char
> *name)
> allocs = p;
> pthread_mutex_unlock(&leak_detective_mutex);
> }
> + if (p + 1 == INVALID_POINTER) {
> + check_invalid_pointer = false; /* sigh! */
> + }
> return p + 1;
> } else {
> return p;
> @@ -128,8 +145,20 @@ void pfree(void *ptr)
> union mhdr *p;
>
> passert(ptr != NULL);
> + if (check_invalid_pointer) {
> + if (ptr == INVALID_POINTER) {
> + PASSERT_FAIL("pointer %p invalid (likely from use after
> free)", p);
> + }
> + }
> +
> p = ((union mhdr *)ptr) - 1;
> - passert(p->i.magic == LEAK_MAGIC);
> +
> + if (p->i.magic == ~LEAK_MAGIC) {
> + PASSERT_FAIL("pointer %p invalid (likely from double free)",
> ptr);
> + } else if (p->i.magic != LEAK_MAGIC) {
> + PASSERT_FAIL("pointer %p invalid (likely from heap corruption)",
> ptr);
> + }
> +
> {
> pthread_mutex_lock(&leak_detective_mutex);
> if (p->i.older != NULL) {
> @@ -146,7 +175,7 @@ void pfree(void *ptr)
> pthread_mutex_unlock(&leak_detective_mutex);
> }
> /* stomp on memory! Is another byte value better? */
> - memset(p, 0xEF, sizeof(union mhdr) + p->i.size);
> + memset(p, INVALID_MAGIC, sizeof(union mhdr) + p->i.size);
> p->i.magic = ~LEAK_MAGIC;
> free(p);
> } else {
>
> _______________________________________________
> Swan-dev mailing list
> Swan-dev@lists.libreswan.org
> https://lists.libreswan.org/mailman/listinfo/swan-dev
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