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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
oid-array.c 
#include "cache.h"
#include "oid-array.h"
#include "sha1-lookup.h"

void oid_array_append(struct oid_array *array, const struct object_id *oid)
{
	ALLOC_GROW(array->oid, array->nr + 1, array->alloc);
	oidcpy(&array->oid[array->nr++], oid);
	array->sorted = 0;
}

static int void_hashcmp(const void *a, const void *b)
{
	return oidcmp(a, b);
}

void oid_array_sort(struct oid_array *array)
{
	if (array->sorted)
		return;
	QSORT(array->oid, array->nr, void_hashcmp);
	array->sorted = 1;
}

static const unsigned char *sha1_access(size_t index, void *table)
{
	struct object_id *array = table;
	return array[index].hash;
}

int oid_array_lookup(struct oid_array *array, const struct object_id *oid)
{
	oid_array_sort(array);
	return sha1_pos(oid->hash, array->oid, array->nr, sha1_access);
}

void oid_array_clear(struct oid_array *array)
{
	FREE_AND_NULL(array->oid);
	array->nr = 0;
	array->alloc = 0;
	array->sorted = 0;
}


int oid_array_for_each(struct oid_array *array,
		       for_each_oid_fn fn,
		       void *data)
{
	size_t i;

	/* No oid_array_sort() here! See oid-array.h */

	for (i = 0; i < array->nr; i++) {
		int ret = fn(array->oid + i, data);
		if (ret)
			return ret;
	}
	return 0;
}

int oid_array_for_each_unique(struct oid_array *array,
			      for_each_oid_fn fn,
			      void *data)
{
	size_t i;

	oid_array_sort(array);

	for (i = 0; i < array->nr; i = oid_array_next_unique(array, i)) {
		int ret = fn(array->oid + i, data);
		if (ret)
			return ret;
	}
	return 0;
}

void oid_array_filter(struct oid_array *array,
		      for_each_oid_fn want,
		      void *cb_data)
{
	size_t nr = array->nr, src, dst;
	struct object_id *oids = array->oid;

	for (src = dst = 0; src < nr; src++) {
		if (want(&oids[src], cb_data)) {
			if (src != dst)
				oidcpy(&oids[dst], &oids[src]);
			dst++;
		}
	}
	array->nr = dst;
}
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