harden REALLOC_ARRAY and xcalloc against size_t overflow

[thirdparty/git.git] / wrapper.c

/*
 * Various trivial helper wrappers around standard functions
 */
#include "cache.h"

static void do_nothing(size_t size)
{
}

static void (*try_to_free_routine)(size_t size) = do_nothing;

static int memory_limit_check(size_t size, int gentle)
{
	static size_t limit = 0;
	if (!limit) {
		limit = git_env_ulong("GIT_ALLOC_LIMIT", 0);
		if (!limit)
			limit = SIZE_MAX;
	}
	if (size > limit) {
		if (gentle) {
			error("attempting to allocate %"PRIuMAX" over limit %"PRIuMAX,
			      (uintmax_t)size, (uintmax_t)limit);
			return -1;
		} else
			die("attempting to allocate %"PRIuMAX" over limit %"PRIuMAX,
			    (uintmax_t)size, (uintmax_t)limit);
	}
	return 0;
}

try_to_free_t set_try_to_free_routine(try_to_free_t routine)
{
	try_to_free_t old = try_to_free_routine;
	if (!routine)
		routine = do_nothing;
	try_to_free_routine = routine;
	return old;
}

char *xstrdup(const char *str)
{
	char *ret = strdup(str);
	if (!ret) {
		try_to_free_routine(strlen(str) + 1);
		ret = strdup(str);
		if (!ret)
			die("Out of memory, strdup failed");
	}
	return ret;
}

static void *do_xmalloc(size_t size, int gentle)
{
	void *ret;

	if (memory_limit_check(size, gentle))
		return NULL;
	ret = malloc(size);
	if (!ret && !size)
		ret = malloc(1);
	if (!ret) {
		try_to_free_routine(size);
		ret = malloc(size);
		if (!ret && !size)
			ret = malloc(1);
		if (!ret) {
			if (!gentle)
				die("Out of memory, malloc failed (tried to allocate %lu bytes)",
				    (unsigned long)size);
			else {
				error("Out of memory, malloc failed (tried to allocate %lu bytes)",
				      (unsigned long)size);
				return NULL;
			}
		}
	}
#ifdef XMALLOC_POISON
	memset(ret, 0xA5, size);
#endif
	return ret;
}

void *xmalloc(size_t size)
{
	return do_xmalloc(size, 0);
}

static void *do_xmallocz(size_t size, int gentle)
{
	void *ret;
	if (unsigned_add_overflows(size, 1)) {
		if (gentle) {
			error("Data too large to fit into virtual memory space.");
			return NULL;
		} else
			die("Data too large to fit into virtual memory space.");
	}
	ret = do_xmalloc(size + 1, gentle);
	if (ret)
		((char*)ret)[size] = 0;
	return ret;
}

void *xmallocz(size_t size)
{
	return do_xmallocz(size, 0);
}

void *xmallocz_gently(size_t size)
{
	return do_xmallocz(size, 1);
}

/*
 * xmemdupz() allocates (len + 1) bytes of memory, duplicates "len" bytes of
 * "data" to the allocated memory, zero terminates the allocated memory,
 * and returns a pointer to the allocated memory. If the allocation fails,
 * the program dies.
 */
void *xmemdupz(const void *data, size_t len)
{
	return memcpy(xmallocz(len), data, len);
}

char *xstrndup(const char *str, size_t len)
{
	char *p = memchr(str, '\0', len);
	return xmemdupz(str, p ? p - str : len);
}

void *xrealloc(void *ptr, size_t size)
{
	void *ret;

	memory_limit_check(size, 0);
	ret = realloc(ptr, size);
	if (!ret && !size)
		ret = realloc(ptr, 1);
	if (!ret) {
		try_to_free_routine(size);
		ret = realloc(ptr, size);
		if (!ret && !size)
			ret = realloc(ptr, 1);
		if (!ret)
			die("Out of memory, realloc failed");
	}
	return ret;
}

void *xcalloc(size_t nmemb, size_t size)
{
	void *ret;

	if (unsigned_mult_overflows(nmemb, size))
		die("data too large to fit into virtual memory space");

	memory_limit_check(size * nmemb, 0);
	ret = calloc(nmemb, size);
	if (!ret && (!nmemb || !size))
		ret = calloc(1, 1);
	if (!ret) {
		try_to_free_routine(nmemb * size);
		ret = calloc(nmemb, size);
		if (!ret && (!nmemb || !size))
			ret = calloc(1, 1);
		if (!ret)
			die("Out of memory, calloc failed");
	}
	return ret;
}

/*
 * Limit size of IO chunks, because huge chunks only cause pain.  OS X
 * 64-bit is buggy, returning EINVAL if len >= INT_MAX; and even in
 * the absence of bugs, large chunks can result in bad latencies when
 * you decide to kill the process.
 *
 * We pick 8 MiB as our default, but if the platform defines SSIZE_MAX
 * that is smaller than that, clip it to SSIZE_MAX, as a call to
 * read(2) or write(2) larger than that is allowed to fail.  As the last
 * resort, we allow a port to pass via CFLAGS e.g. "-DMAX_IO_SIZE=value"
 * to override this, if the definition of SSIZE_MAX given by the platform
 * is broken.
 */
#ifndef MAX_IO_SIZE
# define MAX_IO_SIZE_DEFAULT (8*1024*1024)
# if defined(SSIZE_MAX) && (SSIZE_MAX < MAX_IO_SIZE_DEFAULT)
#  define MAX_IO_SIZE SSIZE_MAX
# else
#  define MAX_IO_SIZE MAX_IO_SIZE_DEFAULT
# endif
#endif

/**
 * xopen() is the same as open(), but it die()s if the open() fails.
 */
int xopen(const char *path, int oflag, ...)
{
	mode_t mode = 0;
	va_list ap;

	/*
	 * va_arg() will have undefined behavior if the specified type is not
	 * compatible with the argument type. Since integers are promoted to
	 * ints, we fetch the next argument as an int, and then cast it to a
	 * mode_t to avoid undefined behavior.
	 */
	va_start(ap, oflag);
	if (oflag & O_CREAT)
		mode = va_arg(ap, int);
	va_end(ap);

	for (;;) {
		int fd = open(path, oflag, mode);
		if (fd >= 0)
			return fd;
		if (errno == EINTR)
			continue;

		if ((oflag & O_RDWR) == O_RDWR)
			die_errno(_("could not open '%s' for reading and writing"), path);
		else if ((oflag & O_WRONLY) == O_WRONLY)
			die_errno(_("could not open '%s' for writing"), path);
		else
			die_errno(_("could not open '%s' for reading"), path);
	}
}

/*
 * xread() is the same a read(), but it automatically restarts read()
 * operations with a recoverable error (EAGAIN and EINTR). xread()
 * DOES NOT GUARANTEE that "len" bytes is read even if the data is available.
 */
ssize_t xread(int fd, void *buf, size_t len)
{
	ssize_t nr;
	if (len > MAX_IO_SIZE)
	    len = MAX_IO_SIZE;
	while (1) {
		nr = read(fd, buf, len);
		if ((nr < 0) && (errno == EAGAIN || errno == EINTR))
			continue;
		return nr;
	}
}

/*
 * xwrite() is the same a write(), but it automatically restarts write()
 * operations with a recoverable error (EAGAIN and EINTR). xwrite() DOES NOT
 * GUARANTEE that "len" bytes is written even if the operation is successful.
 */
ssize_t xwrite(int fd, const void *buf, size_t len)
{
	ssize_t nr;
	if (len > MAX_IO_SIZE)
	    len = MAX_IO_SIZE;
	while (1) {
		nr = write(fd, buf, len);
		if ((nr < 0) && (errno == EAGAIN || errno == EINTR))
			continue;
		return nr;
	}
}

/*
 * xpread() is the same as pread(), but it automatically restarts pread()
 * operations with a recoverable error (EAGAIN and EINTR). xpread() DOES
 * NOT GUARANTEE that "len" bytes is read even if the data is available.
 */
ssize_t xpread(int fd, void *buf, size_t len, off_t offset)
{
	ssize_t nr;
	if (len > MAX_IO_SIZE)
		len = MAX_IO_SIZE;
	while (1) {
		nr = pread(fd, buf, len, offset);
		if ((nr < 0) && (errno == EAGAIN || errno == EINTR))
			continue;
		return nr;
	}
}

ssize_t read_in_full(int fd, void *buf, size_t count)
{
	char *p = buf;
	ssize_t total = 0;

	while (count > 0) {
		ssize_t loaded = xread(fd, p, count);
		if (loaded < 0)
			return -1;
		if (loaded == 0)
			return total;
		count -= loaded;
		p += loaded;
		total += loaded;
	}

	return total;
}

ssize_t write_in_full(int fd, const void *buf, size_t count)
{
	const char *p = buf;
	ssize_t total = 0;

	while (count > 0) {
		ssize_t written = xwrite(fd, p, count);
		if (written < 0)
			return -1;
		if (!written) {
			errno = ENOSPC;
			return -1;
		}
		count -= written;
		p += written;
		total += written;
	}

	return total;
}

ssize_t pread_in_full(int fd, void *buf, size_t count, off_t offset)
{
	char *p = buf;
	ssize_t total = 0;

	while (count > 0) {
		ssize_t loaded = xpread(fd, p, count, offset);
		if (loaded < 0)
			return -1;
		if (loaded == 0)
			return total;
		count -= loaded;
		p += loaded;
		total += loaded;
		offset += loaded;
	}

	return total;
}

int xdup(int fd)
{
	int ret = dup(fd);
	if (ret < 0)
		die_errno("dup failed");
	return ret;
}

/**
 * xfopen() is the same as fopen(), but it die()s if the fopen() fails.
 */
FILE *xfopen(const char *path, const char *mode)
{
	for (;;) {
		FILE *fp = fopen(path, mode);
		if (fp)
			return fp;
		if (errno == EINTR)
			continue;

		if (*mode && mode[1] == '+')
			die_errno(_("could not open '%s' for reading and writing"), path);
		else if (*mode == 'w' || *mode == 'a')
			die_errno(_("could not open '%s' for writing"), path);
		else
			die_errno(_("could not open '%s' for reading"), path);
	}
}

FILE *xfdopen(int fd, const char *mode)
{
	FILE *stream = fdopen(fd, mode);
	if (stream == NULL)
		die_errno("Out of memory? fdopen failed");
	return stream;
}

FILE *fopen_for_writing(const char *path)
{
	FILE *ret = fopen(path, "w");

	if (!ret && errno == EPERM) {
		if (!unlink(path))
			ret = fopen(path, "w");
		else
			errno = EPERM;
	}
	return ret;
}

int xmkstemp(char *template)
{
	int fd;
	char origtemplate[PATH_MAX];
	strlcpy(origtemplate, template, sizeof(origtemplate));

	fd = mkstemp(template);
	if (fd < 0) {
		int saved_errno = errno;
		const char *nonrelative_template;

		if (strlen(template) != strlen(origtemplate))
			template = origtemplate;

		nonrelative_template = absolute_path(template);
		errno = saved_errno;
		die_errno("Unable to create temporary file '%s'",
			nonrelative_template);
	}
	return fd;
}

/* git_mkstemp() - create tmp file honoring TMPDIR variable */
int git_mkstemp(char *path, size_t len, const char *template)
{
	const char *tmp;
	size_t n;

	tmp = getenv("TMPDIR");
	if (!tmp)
		tmp = "/tmp";
	n = snprintf(path, len, "%s/%s", tmp, template);
	if (len <= n) {
		errno = ENAMETOOLONG;
		return -1;
	}
	return mkstemp(path);
}

/* git_mkstemps() - create tmp file with suffix honoring TMPDIR variable. */
int git_mkstemps(char *path, size_t len, const char *template, int suffix_len)
{
	const char *tmp;
	size_t n;

	tmp = getenv("TMPDIR");
	if (!tmp)
		tmp = "/tmp";
	n = snprintf(path, len, "%s/%s", tmp, template);
	if (len <= n) {
		errno = ENAMETOOLONG;
		return -1;
	}
	return mkstemps(path, suffix_len);
}

/* Adapted from libiberty's mkstemp.c. */

#undef TMP_MAX
#define TMP_MAX 16384

int git_mkstemps_mode(char *pattern, int suffix_len, int mode)
{
	static const char letters[] =
		"abcdefghijklmnopqrstuvwxyz"
		"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
		"0123456789";
	static const int num_letters = 62;
	uint64_t value;
	struct timeval tv;
	char *template;
	size_t len;
	int fd, count;

	len = strlen(pattern);

	if (len < 6 + suffix_len) {
		errno = EINVAL;
		return -1;
	}

	if (strncmp(&pattern[len - 6 - suffix_len], "XXXXXX", 6)) {
		errno = EINVAL;
		return -1;
	}

	/*
	 * Replace pattern's XXXXXX characters with randomness.
	 * Try TMP_MAX different filenames.
	 */
	gettimeofday(&tv, NULL);
	value = ((size_t)(tv.tv_usec << 16)) ^ tv.tv_sec ^ getpid();
	template = &pattern[len - 6 - suffix_len];
	for (count = 0; count < TMP_MAX; ++count) {
		uint64_t v = value;
		/* Fill in the random bits. */
		template[0] = letters[v % num_letters]; v /= num_letters;
		template[1] = letters[v % num_letters]; v /= num_letters;
		template[2] = letters[v % num_letters]; v /= num_letters;
		template[3] = letters[v % num_letters]; v /= num_letters;
		template[4] = letters[v % num_letters]; v /= num_letters;
		template[5] = letters[v % num_letters]; v /= num_letters;

		fd = open(pattern, O_CREAT | O_EXCL | O_RDWR, mode);
		if (fd >= 0)
			return fd;
		/*
		 * Fatal error (EPERM, ENOSPC etc).
		 * It doesn't make sense to loop.
		 */
		if (errno != EEXIST)
			break;
		/*
		 * This is a random value.  It is only necessary that
		 * the next TMP_MAX values generated by adding 7777 to
		 * VALUE are different with (module 2^32).
		 */
		value += 7777;
	}
	/* We return the null string if we can't find a unique file name.  */
	pattern[0] = '\0';
	return -1;
}

int git_mkstemp_mode(char *pattern, int mode)
{
	/* mkstemp is just mkstemps with no suffix */
	return git_mkstemps_mode(pattern, 0, mode);
}

#ifdef NO_MKSTEMPS
int gitmkstemps(char *pattern, int suffix_len)
{
	return git_mkstemps_mode(pattern, suffix_len, 0600);
}
#endif

int xmkstemp_mode(char *template, int mode)
{
	int fd;
	char origtemplate[PATH_MAX];
	strlcpy(origtemplate, template, sizeof(origtemplate));

	fd = git_mkstemp_mode(template, mode);
	if (fd < 0) {
		int saved_errno = errno;
		const char *nonrelative_template;

		if (!template[0])
			template = origtemplate;

		nonrelative_template = absolute_path(template);
		errno = saved_errno;
		die_errno("Unable to create temporary file '%s'",
			nonrelative_template);
	}
	return fd;
}

static int warn_if_unremovable(const char *op, const char *file, int rc)
{
	int err;
	if (!rc || errno == ENOENT)
		return 0;
	err = errno;
	warning("unable to %s %s: %s", op, file, strerror(errno));
	errno = err;
	return rc;
}

int unlink_or_msg(const char *file, struct strbuf *err)
{
	int rc = unlink(file);

	assert(err);

	if (!rc || errno == ENOENT)
		return 0;

	strbuf_addf(err, "unable to unlink %s: %s",
		    file, strerror(errno));
	return -1;
}

int unlink_or_warn(const char *file)
{
	return warn_if_unremovable("unlink", file, unlink(file));
}

int rmdir_or_warn(const char *file)
{
	return warn_if_unremovable("rmdir", file, rmdir(file));
}

int remove_or_warn(unsigned int mode, const char *file)
{
	return S_ISGITLINK(mode) ? rmdir_or_warn(file) : unlink_or_warn(file);
}

void warn_on_inaccessible(const char *path)
{
	warning(_("unable to access '%s': %s"), path, strerror(errno));
}

static int access_error_is_ok(int err, unsigned flag)
{
	return err == ENOENT || err == ENOTDIR ||
		((flag & ACCESS_EACCES_OK) && err == EACCES);
}

int access_or_warn(const char *path, int mode, unsigned flag)
{
	int ret = access(path, mode);
	if (ret && !access_error_is_ok(errno, flag))
		warn_on_inaccessible(path);
	return ret;
}

int access_or_die(const char *path, int mode, unsigned flag)
{
	int ret = access(path, mode);
	if (ret && !access_error_is_ok(errno, flag))
		die_errno(_("unable to access '%s'"), path);
	return ret;
}

char *xgetcwd(void)
{
	struct strbuf sb = STRBUF_INIT;
	if (strbuf_getcwd(&sb))
		die_errno(_("unable to get current working directory"));
	return strbuf_detach(&sb, NULL);
}

int xsnprintf(char *dst, size_t max, const char *fmt, ...)
{
	va_list ap;
	int len;

	va_start(ap, fmt);
	len = vsnprintf(dst, max, fmt, ap);
	va_end(ap);

	if (len < 0)
		die("BUG: your snprintf is broken");
	if (len >= max)
		die("BUG: attempt to snprintf into too-small buffer");
	return len;
}

static int write_file_v(const char *path, int fatal,
			const char *fmt, va_list params)
{
	struct strbuf sb = STRBUF_INIT;
	int fd = open(path, O_RDWR | O_CREAT | O_TRUNC, 0666);
	if (fd < 0) {
		if (fatal)
			die_errno(_("could not open %s for writing"), path);
		return -1;
	}
	strbuf_vaddf(&sb, fmt, params);
	strbuf_complete_line(&sb);
	if (write_in_full(fd, sb.buf, sb.len) != sb.len) {
		int err = errno;
		close(fd);
		strbuf_release(&sb);
		errno = err;
		if (fatal)
			die_errno(_("could not write to %s"), path);
		return -1;
	}
	strbuf_release(&sb);
	if (close(fd)) {
		if (fatal)
			die_errno(_("could not close %s"), path);
		return -1;
	}
	return 0;
}

int write_file(const char *path, const char *fmt, ...)
{
	int status;
	va_list params;

	va_start(params, fmt);
	status = write_file_v(path, 1, fmt, params);
	va_end(params);
	return status;
}

int write_file_gently(const char *path, const char *fmt, ...)
{
	int status;
	va_list params;

	va_start(params, fmt);
	status = write_file_v(path, 0, fmt, params);
	va_end(params);
	return status;
}

void sleep_millisec(int millisec)
{
	poll(NULL, 0, millisec);
}