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sys/net/gnrc_pktbuf_static: add double free detection #20974

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merged 2 commits into from
Nov 16, 2024
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sys/net/gnrc_pktbuf_static: add double free detection #20974

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4bd273f
sys/net/gnrc_pktbuf_static: add double free detection
benpicco Nov 11, 2024
982af61
sys/net/gnrc_pktbuf_static: make hexdump optional
benpicco Nov 11, 2024
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19 changes: 13 additions & 6 deletions sys/net/gnrc/pktbuf_static/gnrc_pktbuf_static.c
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Original file line number Diff line number Diff line change
Expand Up @@ -240,12 +240,13 @@ gnrc_pktsnip_t *gnrc_pktbuf_start_write(gnrc_pktsnip_t *pkt)
}

#ifdef DEVELHELP
#ifdef MODULE_OD
static inline void _print_chunk(void *chunk, size_t size, int num)
{
printf("=========== chunk %3i (%-10p size: %4" PRIuSIZE ") ===========\n", num, chunk,
size);
#ifdef MODULE_OD
od_hex_dump(chunk, size, OD_WIDTH_DEFAULT);
#endif
}

static inline void _print_ptr(_unused_t *ptr)
Expand All @@ -266,11 +267,9 @@ static inline void _print_unused(_unused_t *ptr)
_print_ptr(ptr->next);
printf(", size: %4u) ~\n", ptr->size);
}
#endif

void gnrc_pktbuf_stats(void)
{
#ifdef MODULE_OD
_unused_t *ptr = _first_unused;
uint8_t *chunk = &_static_buf[0];
int count = 0;
Expand Down Expand Up @@ -306,9 +305,6 @@ void gnrc_pktbuf_stats(void)
if (chunk <= &_static_buf[CONFIG_GNRC_PKTBUF_SIZE - 1]) {
_print_chunk(chunk, &_static_buf[CONFIG_GNRC_PKTBUF_SIZE] - chunk, count);
}
#else
DEBUG("pktbuf: needs od module\n");
#endif
}
#endif

Expand Down Expand Up @@ -438,6 +434,10 @@ static void *_pktbuf_alloc(size_t size)
#endif
assert(0);
}
if (CONFIG_GNRC_PKTBUF_CHECK_USE_AFTER_FREE) {
/* clear out canary */
memset(ptr, ~CANARY, size);
}

return (void *)ptr;
}
Expand Down Expand Up @@ -469,6 +469,13 @@ void gnrc_pktbuf_free_internal(void *data, size_t size)
}

if (CONFIG_GNRC_PKTBUF_CHECK_USE_AFTER_FREE) {
/* check if the data has already been marked as free */
size_t chk_len = _align(size) - sizeof(*new);
if (chk_len && !memchk((uint8_t *)data + sizeof(*new), CANARY, chk_len)) {
printf("pktbuf: double free detected! (at %p, len=%u)\n",
data, (unsigned)_align(size));
DEBUG_BREAKPOINT(2);
}
memset(data, CANARY, _align(size));
}

Expand Down
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