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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
stripspace.c 
#include "builtin.h"
#include "cache.h"
#include "config.h"
#include "parse-options.h"
#include "strbuf.h"

static void comment_lines(struct strbuf *buf)
{
	char *msg;
	size_t len;

	msg = strbuf_detach(buf, &len);
	strbuf_add_commented_lines(buf, msg, len);
	free(msg);
}

static const char * const stripspace_usage[] = {
	N_("git stripspace [-s | --strip-comments]"),
	N_("git stripspace [-c | --comment-lines]"),
	NULL
};

enum stripspace_mode {
	STRIP_DEFAULT = 0,
	STRIP_COMMENTS,
	COMMENT_LINES
};

int cmd_stripspace(int argc, const char **argv, const char *prefix)
{
	struct strbuf buf = STRBUF_INIT;
	enum stripspace_mode mode = STRIP_DEFAULT;
	int nongit;

	const struct option options[] = {
		OPT_CMDMODE('s', "strip-comments", &mode,
			    N_("skip and remove all lines starting with comment character"),
			    STRIP_COMMENTS),
		OPT_CMDMODE('c', "comment-lines", &mode,
			    N_("prepend comment character and space to each line"),
			    COMMENT_LINES),
		OPT_END()
	};

	argc = parse_options(argc, argv, prefix, options, stripspace_usage, 0);
	if (argc)
		usage_with_options(stripspace_usage, options);

	if (mode == STRIP_COMMENTS || mode == COMMENT_LINES) {
		setup_git_directory_gently(&nongit);
		git_config(git_default_config, NULL);
	}

	if (strbuf_read(&buf, 0, 1024) < 0)
		die_errno("could not read the input");

	if (mode == STRIP_DEFAULT || mode == STRIP_COMMENTS)
		strbuf_stripspace(&buf, mode == STRIP_COMMENTS);
	else
		comment_lines(&buf);

	write_or_die(1, buf.buf, buf.len);
	strbuf_release(&buf);
	return 0;
}
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