Re: [PATCH] src/ext4_resize.c: set errno to 0 before the strtoull call

["H.J. Lu" <hjl.tools@gmail.com>]

On Tue, Jan 18, 2022 at 6:43 AM Yann Droneaud <ydroneaud@opteya.com> wrote:
>
> Hi,
>
> Le 18/01/2022 à 15:29, H.J. Lu via Libc-alpha a écrit :
> > On Tue, Jan 18, 2022 at 6:22 AM Andreas Schwab <schwab@linux-m68k.org> wrote:
> >> On Jan 18 2022, xuyang2018.jy@fujitsu.com wrote:
> >>
> >>> Now, I use glibc-2.34 and run the following program[1] but the errno is
> >>> not 0 in the beginning. So is this a known bug on glibc-2.34(Theodore
> >>> doesn't meet this problem on glicb-2.31)?
> >>>
> >>> [1]https://git.kernel.org/pub/scm/fs/xfs/xfstests-dev.git/tree/src/ext4_resize.c
> >> Note that there is a call to open preceding the strtoull call, so no
> >> guarantees can be made about the value of errno before the latter.
> >>
> > strtoull man page:
> >
> > RETURN VALUE
> >         The strtoul() function returns either the result of the conversion  or,
> >         if  there  was  a leading minus sign, the negation of the result of the
> >         conversion represented as an unsigned value, unless the original  (non‐
> >         negated)  value  would  overflow; in the latter case, strtoul() returns
> >         ULONG_MAX and sets errno to ERANGE.  Precisely the same holds for  str‐
> >         toull() (with ULLONG_MAX instead of ULONG_MAX).
> >
> > new_size = strtoull(argv[2], &tmp, 10);
> > if ((errno) || (*tmp != '\0')) {
> > ^^^^^^^^^^^^ Shouldn't errno be checked only after the prior function
> > return value is checked first?
> >
> > fprintf(stderr, "%s: invalid new size\n", argv[0]);
> > return 1;
> > }
>
> Something like:
>
>          errno = 0; /* must be cleared to distinguish error */
^^^^^^^^^^^^^^^^^ Remove it.
>          tmp = NULL;
>          new_size = strtoull(argv[2], &p, 0);
>          if ((new_size == 0 || new_size == ULONGLONG_MAX) && errno) {
 Change it to

if (new_size == 0 || (new_size == ULONGLONG_MAX) && errno)) {
>                 fprintf(stderr, "%s: invalid new size\n", argv[0]);
>                 return 1;
>         }
>
>          if (tmp) {
>                  /* error, unused trailing characters */
>                  if (*tmp) {
>                         fprintf(stderr, "%s: invalid new size\n", argv[0]);
>                         return 1;
>                  }
>
>                  /* error, empty string */
>                  if (tmp == argv[2]) {
>                         fprintf(stderr, "%s: invalid new size\n", argv[0]);
>                         return 1;
>
>                  }
>          }
>
> --
> Yann Droneaud
> OPTEYA
>


-- 
H.J.