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stat: do not rely on undefined behavior in printf formats

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* src/stat.c (digits, printf_flags): New static vars.
(make_format): New function.
(out_string, out_int, out_uint, out_uint_o, out_uint_x):
(out_minus_zero): Use it to avoid undefined behavior when invoking
printf.
(print_it): Check for invalid conversion specifications such as
%..X and %1-X, which would otherwise rely on undefined behavior
when invoking printf.
* tests/misc/stat-nanoseconds: Check that the "I" printf flag
doesn't mess up in the C locale, as it formerly did on non-GNU
hosts.
This commit is contained in:
Paul Eggert
2010-11-06 13:57:08 -07:00
parent 6c058b2dab
commit ca9aa75960
2 changed files with 41 additions and 7 deletions
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47
src/stat.c
View File

@@ -150,6 +150,16 @@ statfs (char const *filename, struct fs_info *buf)
#define hextobin(c) ((c) >= 'a' && (c) <= 'f' ? (c) - 'a' + 10 : \
(c) >= 'A' && (c) <= 'F' ? (c) - 'A' + 10 : (c) - '0')
static char const digits[] = "0123456789";
/* Flags that are portable for use in printf, for at least one
conversion specifier; make_format removes unportable flags as
needed for particular specifiers. The glibc 2.2 extension "I" is
listed here; it is removed by make_format because it has undefined
behavior elsewhere and because it is incompatible with
out_epoch_sec. */
static char const printf_flags[] = "'-+ #0I";
#define PROGRAM_NAME "stat"
#define AUTHORS proper_name ("Michael Meskes")
@@ -467,40 +477,59 @@ human_time (struct timespec t)
return str;
}
/* PFORMAT points to a '%' followed by a prefix of a format, all of
size PREFIX_LEN. The flags allowed for this format are
ALLOWED_FLAGS; remove other printf flags from the prefix, then
append SUFFIX. */
static void
make_format (char *pformat, size_t prefix_len, char const *allowed_flags,
char const *suffix)
{
char *dst = pformat + 1;
char const *src;
char const *srclim = pformat + prefix_len;
for (src = dst; src < srclim && strchr (printf_flags, *src); src++)
if (strchr (allowed_flags, *src))
*dst++ = *src;
while (src < srclim)
*dst++ = *src++;
strcpy (dst, suffix);
}
static void
out_string (char *pformat, size_t prefix_len, char const *arg)
{
strcpy (pformat + prefix_len, "s");
make_format (pformat, prefix_len, "-", "s");
printf (pformat, arg);
}
static int
out_int (char *pformat, size_t prefix_len, intmax_t arg)
{
strcpy (pformat + prefix_len, PRIdMAX);
make_format (pformat, prefix_len, "'-+ 0", PRIdMAX);
return printf (pformat, arg);
}
static int
out_uint (char *pformat, size_t prefix_len, uintmax_t arg)
{
strcpy (pformat + prefix_len, PRIuMAX);
make_format (pformat, prefix_len, "'-0", PRIuMAX);
return printf (pformat, arg);
}
static void
out_uint_o (char *pformat, size_t prefix_len, uintmax_t arg)
{
strcpy (pformat + prefix_len, PRIoMAX);
make_format (pformat, prefix_len, "-#0", PRIoMAX);
printf (pformat, arg);
}
static void
out_uint_x (char *pformat, size_t prefix_len, uintmax_t arg)
{
strcpy (pformat + prefix_len, PRIxMAX);
make_format (pformat, prefix_len, "-#0", PRIxMAX);
printf (pformat, arg);
}
static int
out_minus_zero (char *pformat, size_t prefix_len)
{
strcpy (pformat + prefix_len, ".0f");
make_format (pformat, prefix_len, "'-+ 0", ".0f");
return printf (pformat, -0.25);
}
@@ -1028,8 +1057,12 @@ print_it (char const *format, char const *filename,
{
case '%':
{
size_t len = strspn (b + 1, "#-+.I 0123456789");
size_t len = strspn (b + 1, printf_flags);
char const *fmt_char = b + len + 1;
fmt_char += strspn (fmt_char, digits);
if (*fmt_char == '.')
fmt_char += 1 + strspn (fmt_char + 1, digits);
len = fmt_char - (b + 1);
unsigned int fmt_code = *fmt_char;
memcpy (dest, b, len + 1);

1
tests/misc/stat-nanoseconds
View File

@@ -39,6 +39,7 @@ test "$(stat -c %13.6X k)" = ' 67413.023456' || fail=1
test "$(stat -c %013.6X k)" = 067413.023456 || fail=1
test "$(stat -c %-13.6X k)" = '67413.023456 ' || fail=1
test "$(stat -c %18.10X k)" = ' 67413.0234567890' || fail=1
test "$(stat -c %I18.10X k)" = ' 67413.0234567890' || fail=1
test "$(stat -c %018.10X k)" = 0067413.0234567890 || fail=1
test "$(stat -c %-18.10X k)" = '67413.0234567890 ' || fail=1