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libio: Fix fmemopen append mode failure (BZ# 20012)

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The fmemopen implementation does not account the file position correctly in
append mode. The following example shows the failure:

===
int main ()
{
  char buf[10] = "test";
  FILE *fp = fmemopen (buf, 10, "a+");
  fseek (fp, 0, SEEK_SET);

  int gr;
  if ((gr = getc (fp)) != 't' ||
      (gr = getc (fp)) != 'e' ||
      (gr = getc (fp)) != 's' ||
      (gr = getc (fp)) != 't' ||
      (gr = getc (fp)) != EOF)
    {
      printf ("%s: getc failed returned %i\n", __FUNCTION__, gr);
      return 1;
    }

  return 0;
}
===

This is due both how read and write operation update the buffer position,
taking in consideration buffer lenght instead of maximum position defined
by the open mode.  This patch fixes it and also fixes fseek not returning
EINVAL for invalid whence modes.

Tested on x86_64 and i686.

	[BZ #20012]
	* libio/fmemopen.c (fmemopen_read): Use buffer maximum position, not
	length to calculate the buffer to read.
	(fmemopen_write): Set the buffer position based on bytes written.
	(fmemopen_seek): Return EINVAL for invalid whence modes.
This commit is contained in:
Adhemerval Zanella 2016-04-27 11:51:01 -03:00
parent 0cb313f7cb
commit b65b205fbc
3 changed files with 138 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
ChangeLog
View File

@ -1,5 +1,11 @@
2016-04-29 Adhemerval Zanella <adhemerval.zanella@linaro.org>
[BZ #20012]
* libio/fmemopen.c (fmemopen_read): Use buffer maximum position, not
length to calculate the buffer to read.
(fmemopen_write): Set the buffer position based on bytes written.
(fmemopen_seek): Return EINVAL for invalid whence modes.
[BZ #19957]
* sysdeps/unix/sysv/linux/Makefile [$(subdir) == nptl] (test): Remove
tst-getpid2.

28
libio/fmemopen.c
View File

@ -50,16 +50,14 @@ fmemopen_read (void *cookie, char *b, size_t s)
if (c->pos + s > c->maxpos)
{
if ((size_t) c->pos == c->maxpos)
return 0;
s = c->size - c->pos;
s = c->maxpos - c->pos;
if ((size_t) c->pos > c->maxpos)
s = 0;
}
memcpy (b, &(c->buffer[c->pos]), s);
c->pos += s;
if ((size_t) c->pos > c->maxpos)
c->maxpos = c->pos;
return s;
}
@ -70,28 +68,29 @@ fmemopen_write (void *cookie, const char *b, size_t s)
{
fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie;;
_IO_off64_t pos = c->append ? c->maxpos : c->pos;
int addnullc;
int addnullc = (s == 0 || b[s - 1] != '\0');
addnullc = (s == 0 || b[s - 1] != '\0');
if (pos + s + addnullc > c->size)
if (pos + s > c->size)
{
if ((size_t) (c->pos + addnullc) >= c->size)
{
__set_errno (ENOSPC);
return 0;
}
s = c->size - pos - addnullc;
s = c->size - pos;
}
memcpy (&(c->buffer[pos]), b, s);
c->pos += s;
c->pos = pos + s;
if ((size_t) c->pos > c->maxpos)
{
c->maxpos = c->pos;
if (addnullc)
if (c->maxpos < c->size && addnullc)
c->buffer[c->maxpos] = '\0';
/* A null byte is written in a stream open for update iff it fits. */
else if (c->append == 0 && addnullc != 0)
c->buffer[c->size-1] = '\0';
}
return s;
@ -123,7 +122,10 @@ fmemopen_seek (void *cookie, _IO_off64_t *p, int w)
}
if (np < 0 || (size_t) np > c->size)
return -1;
{
__set_errno (EINVAL);
return -1;
}
*p = c->pos = np;

118
stdio-common/tst-fmemopen3.c
View File

@ -25,8 +25,13 @@ static void
print_buffer (const char *s, size_t n)
{
size_t i;
printf ("{");
for (i=0; i<n; ++i)
printf ("0x%02X (%c), ", s[i], s[i]);
{
printf ("0x%02X (%c)", s[i], s[i]);
if (i != n)
printf (", ");
}
}
/* This test check append mode initial position (a/a+) based on POSIX defition
@ -185,6 +190,112 @@ do_test_read_seek_negative (void)
return ret;
}
static int
do_test_write_append_2 (const char *str)
{
char buf[10];
size_t strn = strlen (str);
strcpy (buf, str);
FILE *fp = fmemopen (buf, sizeof (buf), "a+");
size_t r = ftell (fp);
size_t e = strlen (buf);
if (r != e)
{
printf ("%s: ftell returned %zu, expected %zu\n", __FUNCTION__, r, e);
return 1;
}
if (fseek (fp, 0, SEEK_SET) == -1)
{
printf ("%s: fseek returned -1\n", __FUNCTION__);
return 1;
}
int gr;
for (int i=0; i<strn; ++i)
{
if ((gr = getc (fp)) != str[i])
{
printf ("%s: getc failed returned %d, expected %d\n", __FUNCTION__,
gr, str[i]);
return 1;
}
}
if ((gr = getc (fp)) != EOF)
{
printf ("%s: getc failed returned %d, expected EOF\n", __FUNCTION__,
gr);
return 1;
}
if (fseek (fp, e+1, SEEK_SET) == -1)
{
printf ("%s: fseek returned -1\n", __FUNCTION__);
return 1;
}
if ((r = ftell (fp)) != e+1)
{
printf ("%s: ftell returned %zu, expected %zu\n", __FUNCTION__, r, e+1);
return 1;
}
if ((gr = getc (fp)) != EOF)
{
printf ("%s: getc failed returned %i\n", __FUNCTION__, gr);
return 1;
}
/* Check if internal position is not changed with a getc returning EOF. */
if ((r = ftell (fp)) != e+1)
{
printf ("%s: ftell returned %zu, expected %zu\n", __FUNCTION__, r, e+1);
return 1;
}
if (fseek (fp, 0, SEEK_CUR) == -1)
{
printf ("%s: fseek returned -1\n", __FUNCTION__);
return 1;
}
/* This should be overwritten by fprintf + fflush. */
buf[e+2] = 'X';
if ((r = fprintf (fp, "%d", 101)) != 3)
{
printf ("%s: fprintf returned %zu, expected %d\n", __FUNCTION__, r, 3);
return 1;
}
fflush (fp);
/* Check if internal position is changed by 3 (strlen of '101'). */
if ((r = ftell (fp)) != e+3)
{
printf ("%s: ftell returned %zu, expected %zu\n", __FUNCTION__, r, e+3);
return 1;
}
char exp[20];
sprintf (exp, "%s%d", str, 101);
if (memcmp (buf, exp, strlen (exp)) != 0)
{
printf ("%s: check failed:", __FUNCTION__);
printf ("\nexpected: ");
print_buffer (buf, sizeof (buf));
printf ("\nbuffer: ");
print_buffer (exp, sizeof (exp));
printf ("\n");
return 1;
}
fclose(fp);
return 0;
}
static int
do_test (void)
{
@ -199,6 +310,11 @@ do_test (void)
ret += do_test_read_seek_negative ();
/* First test plus addend will fit in the define buffer of size 10. */
ret += do_test_write_append_2 ("test");
/* The second test will also fit, but not the final '\0'. */
ret += do_test_write_append_2 ("testing");
return ret;
}