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Revision 447ac906e189535e77dcb1f4bbe3f1bc917d4c12 authored by Patrick Steinhardt on 01 December 2022, 14:45:31 UTC, committed by Junio C Hamano on 05 December 2022, 06:14:16 UTC 
attr: fix out-of-bounds read with unreasonable amount of patterns
 
The `struct attr_stack` tracks the stack of all patterns together with
their attributes. When parsing a gitattributes file that has more than
2^31 such patterns though we may trigger multiple out-of-bounds reads on
64 bit platforms. This is because while the `num_matches` variable is an
unsigned integer, we always use a signed integer to iterate over them.

I have not been able to reproduce this issue due to memory constraints
on my systems. But despite the out-of-bounds reads, the worst thing that
can seemingly happen is to call free(3P) with a garbage pointer when
calling `attr_stack_free()`.

Fix this bug by using unsigned integers to iterate over the array. While
this makes the iteration somewhat awkward when iterating in reverse, it
is at least better than knowingly running into an out-of-bounds read.
While at it, convert the call to `ALLOC_GROW` to use `ALLOC_GROW_BY`
instead.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
1 parent 34ace8b
Raw File
strvec.c 
#include "cache.h"
#include "strvec.h"
#include "strbuf.h"

const char *empty_strvec[] = { NULL };

void strvec_init(struct strvec *array)
{
	array->v = empty_strvec;
	array->nr = 0;
	array->alloc = 0;
}

static void strvec_push_nodup(struct strvec *array, const char *value)
{
	if (array->v == empty_strvec)
		array->v = NULL;

	ALLOC_GROW(array->v, array->nr + 2, array->alloc);
	array->v[array->nr++] = value;
	array->v[array->nr] = NULL;
}

const char *strvec_push(struct strvec *array, const char *value)
{
	strvec_push_nodup(array, xstrdup(value));
	return array->v[array->nr - 1];
}

const char *strvec_pushf(struct strvec *array, const char *fmt, ...)
{
	va_list ap;
	struct strbuf v = STRBUF_INIT;

	va_start(ap, fmt);
	strbuf_vaddf(&v, fmt, ap);
	va_end(ap);

	strvec_push_nodup(array, strbuf_detach(&v, NULL));
	return array->v[array->nr - 1];
}

void strvec_pushl(struct strvec *array, ...)
{
	va_list ap;
	const char *arg;

	va_start(ap, array);
	while ((arg = va_arg(ap, const char *)))
		strvec_push(array, arg);
	va_end(ap);
}

void strvec_pushv(struct strvec *array, const char **items)
{
	for (; *items; items++)
		strvec_push(array, *items);
}

void strvec_pop(struct strvec *array)
{
	if (!array->nr)
		return;
	free((char *)array->v[array->nr - 1]);
	array->v[array->nr - 1] = NULL;
	array->nr--;
}

void strvec_split(struct strvec *array, const char *to_split)
{
	while (isspace(*to_split))
		to_split++;
	for (;;) {
		const char *p = to_split;

		if (!*p)
			break;

		while (*p && !isspace(*p))
			p++;
		strvec_push_nodup(array, xstrndup(to_split, p - to_split));

		while (isspace(*p))
			p++;
		to_split = p;
	}
}

void strvec_clear(struct strvec *array)
{
	if (array->v != empty_strvec) {
		int i;
		for (i = 0; i < array->nr; i++)
			free((char *)array->v[i]);
		free(array->v);
	}
	strvec_init(array);
}

const char **strvec_detach(struct strvec *array)
{
	if (array->v == empty_strvec)
		return xcalloc(1, sizeof(const char *));
	else {
		const char **ret = array->v;
		strvec_init(array);
		return ret;
	}
}
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