On 2023-05-31 22:56:22+0200, Alejandro Colomar wrote:
> On 5/30/23 18:40, Thomas Weißschuh wrote:
> > POSIX does not allow "tv" to be NULL.
> >
> > On glibc and gnulib calling gettimeofday(NULL, NULL) can segfault.
> >
> > For glibc see __gettimeofday() and __gettimeofday64() in
> > sysdeps/unix/sysv/linux/gettimeofday.c.
> >
> > Note that by default glibc may use the gettimeofday() syscall or vdso
> > function which both support "tv" to be NULL.
> > The segfault can be triggered by compiling a i386 binary on a x86_64
> > system.
>
> What happens with the Linux syscall? What does it do for NULL in tv?
It returns "0". Same for the VDSO and musl libc.
>
> Thanks,
> Alex
>
> >
> > Signed-off-by: Thomas Weißschuh <thomas@xxxxxxxx>
> > ---
> > man2/gettimeofday.2 | 10 ++++------
> > 1 file changed, 4 insertions(+), 6 deletions(-)
> >
> > diff --git a/man2/gettimeofday.2 b/man2/gettimeofday.2
> > index 9d134fa49de7..cdbec5ede23c 100644
> > --- a/man2/gettimeofday.2
> > +++ b/man2/gettimeofday.2
> > @@ -85,16 +85,14 @@ struct timezone {
> > .EE
> > .in
> > .PP
> > -If either
> > -.I tv
> > -or
> > +If
> > .I tz
> > -is NULL, the corresponding structure is not set or returned.
> > +is NULL, the structure is not set or returned.
> > .\" FIXME . The compilation warning looks to be going away in glibc 2.17
> > .\" see glibc commit 4b7634a5e03b0da6f8875de9d3f74c1cf6f2a6e8
> > -(However, compilation warnings will result if
> > +If
> > .I tv
> > -is NULL.)
> > +is NULL, the behavior is unspecified.
> > .\" The following is covered under EPERM below:
> > .\" .PP
> > .\" Only the superuser may use
> >
> > ---
> > base-commit: f0067f73941ea0e512b9018a123472508a0858db
> > change-id: 20230530-gettimeofday-null-7ee404b7825f
> >
> > Best regards,
>
> --
> <http://www.alejandro-colomar.es/>
> GPG key fingerprint: A9348594CE31283A826FBDD8D57633D441E25BB5
