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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
http-fetch.c 
#include "cache.h"
#include "config.h"
#include "exec-cmd.h"
#include "http.h"
#include "walker.h"

static const char http_fetch_usage[] = "git http-fetch "
"[-c] [-t] [-a] [-v] [--recover] [-w ref] [--stdin | --packfile=hash | commit-id] url";

static int fetch_using_walker(const char *raw_url, int get_verbosely,
			      int get_recover, int commits, char **commit_id,
			      const char **write_ref, int commits_on_stdin)
{
	char *url = NULL;
	struct walker *walker;
	int rc;

	str_end_url_with_slash(raw_url, &url);

	http_init(NULL, url, 0);

	walker = get_http_walker(url);
	walker->get_verbosely = get_verbosely;
	walker->get_recover = get_recover;
	walker->get_progress = 0;

	rc = walker_fetch(walker, commits, commit_id, write_ref, url);

	if (commits_on_stdin)
		walker_targets_free(commits, commit_id, write_ref);

	if (walker->corrupt_object_found) {
		fprintf(stderr,
"Some loose object were found to be corrupt, but they might be just\n"
"a false '404 Not Found' error message sent with incorrect HTTP\n"
"status code.  Suggest running 'git fsck'.\n");
	}

	walker_free(walker);
	http_cleanup();
	free(url);

	return rc;
}

static void fetch_single_packfile(struct object_id *packfile_hash,
				  const char *url) {
	struct http_pack_request *preq;
	struct slot_results results;
	int ret;

	http_init(NULL, url, 0);

	preq = new_direct_http_pack_request(packfile_hash->hash, xstrdup(url));
	if (preq == NULL)
		die("couldn't create http pack request");
	preq->slot->results = &results;
	preq->generate_keep = 1;

	if (start_active_slot(preq->slot)) {
		run_active_slot(preq->slot);
		if (results.curl_result != CURLE_OK) {
			die("Unable to get pack file %s\n%s", preq->url,
			    curl_errorstr);
		}
	} else {
		die("Unable to start request");
	}

	if ((ret = finish_http_pack_request(preq)))
		die("finish_http_pack_request gave result %d", ret);

	release_http_pack_request(preq);
	http_cleanup();
}

int cmd_main(int argc, const char **argv)
{
	int commits_on_stdin = 0;
	int commits;
	const char **write_ref = NULL;
	char **commit_id;
	int arg = 1;
	int get_verbosely = 0;
	int get_recover = 0;
	int packfile = 0;
	int nongit;
	struct object_id packfile_hash;

	setup_git_directory_gently(&nongit);

	while (arg < argc && argv[arg][0] == '-') {
		const char *p;

		if (argv[arg][1] == 't') {
		} else if (argv[arg][1] == 'c') {
		} else if (argv[arg][1] == 'a') {
		} else if (argv[arg][1] == 'v') {
			get_verbosely = 1;
		} else if (argv[arg][1] == 'w') {
			write_ref = &argv[arg + 1];
			arg++;
		} else if (argv[arg][1] == 'h') {
			usage(http_fetch_usage);
		} else if (!strcmp(argv[arg], "--recover")) {
			get_recover = 1;
		} else if (!strcmp(argv[arg], "--stdin")) {
			commits_on_stdin = 1;
		} else if (skip_prefix(argv[arg], "--packfile=", &p)) {
			const char *end;

			packfile = 1;
			if (parse_oid_hex(p, &packfile_hash, &end) || *end)
				die(_("argument to --packfile must be a valid hash (got '%s')"), p);
		}
		arg++;
	}
	if (argc != arg + 2 - (commits_on_stdin || packfile))
		usage(http_fetch_usage);

	if (nongit)
		die(_("not a git repository"));

	git_config(git_default_config, NULL);

	if (packfile) {
		fetch_single_packfile(&packfile_hash, argv[arg]);
		return 0;
	}

	if (commits_on_stdin) {
		commits = walker_targets_stdin(&commit_id, &write_ref);
	} else {
		commit_id = (char **) &argv[arg++];
		commits = 1;
	}
	return fetch_using_walker(argv[arg], get_verbosely, get_recover,
				  commits, commit_id, write_ref,
				  commits_on_stdin);
}
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