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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
qsort_s.c 
#include "../git-compat-util.h"

/*
 * A merge sort implementation, simplified from the qsort implementation
 * by Mike Haertel, which is a part of the GNU C Library.
 * Added context pointer, safety checks and return value.
 */

static void msort_with_tmp(void *b, size_t n, size_t s,
			   int (*cmp)(const void *, const void *, void *),
			   char *t, void *ctx)
{
	char *tmp;
	char *b1, *b2;
	size_t n1, n2;

	if (n <= 1)
		return;

	n1 = n / 2;
	n2 = n - n1;
	b1 = b;
	b2 = (char *)b + (n1 * s);

	msort_with_tmp(b1, n1, s, cmp, t, ctx);
	msort_with_tmp(b2, n2, s, cmp, t, ctx);

	tmp = t;

	while (n1 > 0 && n2 > 0) {
		if (cmp(b1, b2, ctx) <= 0) {
			memcpy(tmp, b1, s);
			tmp += s;
			b1 += s;
			--n1;
		} else {
			memcpy(tmp, b2, s);
			tmp += s;
			b2 += s;
			--n2;
		}
	}
	if (n1 > 0)
		memcpy(tmp, b1, n1 * s);
	memcpy(b, t, (n - n2) * s);
}

int git_qsort_s(void *b, size_t n, size_t s,
		int (*cmp)(const void *, const void *, void *), void *ctx)
{
	const size_t size = st_mult(n, s);
	char buf[1024];

	if (!n)
		return 0;
	if (!b || !cmp)
		return -1;

	if (size < sizeof(buf)) {
		/* The temporary array fits on the small on-stack buffer. */
		msort_with_tmp(b, n, s, cmp, buf, ctx);
	} else {
		/* It's somewhat large, so malloc it.  */
		char *tmp = xmalloc(size);
		msort_with_tmp(b, n, s, cmp, tmp, ctx);
		free(tmp);
	}
	return 0;
}
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