[Bug libc/1952] New: time() returns incorrect value when given bad address

[Bug libc/1952] New: time() returns incorrect value when given bad address

[michael dot kerrisk at gmx dot net]

When the program below is run on Linux/x86, the following output 
is produced:

After time():            t=-14, errno=0
After syscall(SYS_time): t=-1, errno=14

In the first line, the reported return value from time() should be 
-1, with errno set to EFAULT (14).  Instead, the call returns -14.

Could this be a configuration problem in 
sysdeps/unix/sysv/linux/i386/syscalls.list?

Cheers,

Michael

==========

#define _GNU_SOURCE
#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <time.h>

#define VAL 1000

int main() {
    time_t t;

    t = time((time_t *)VAL);
    printf("After time():            t=%ld, errno=%d\n", (long) t, errno);
    t = syscall(SYS_time, (time_t *)VAL);
    printf("After syscall(SYS_time): t=%ld, errno=%d\n", (long) t, errno);
    return 0;
}

-- 
           Summary: time() returns incorrect value when given bad address
           Product: glibc
           Version: 2.3.5
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper at redhat dot com
        ReportedBy: michael dot kerrisk at gmx dot net
                CC: glibc-bugs at sources dot redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=1952

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[Bug libc/1952] time() returns incorrect value when given bad address

[jakub at redhat dot com]

------- Additional Comments From jakub at redhat dot com  2005-11-30 16:18 -------
time is marked with E, i.e. not returning error (which I'd say matches
POSIX which doesn't define any errors for time).  By passing an invalid
address to the function you reach undefined behaviour territory and all answers
are fine in that case.

-- 


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[Bug libc/1952] time() returns incorrect value when given bad address

[michael dot kerrisk at gmx dot net]

------- Additional Comments From michael dot kerrisk at gmx dot net  2005-11-30 16:31 -------
Subject: Re:  time() returns incorrect value when given bad address

> time is marked with E, i.e. not returning error (which I'd say matches
> POSIX which doesn't define any errors for time).  By passing an invalid
> address to the function you reach undefined behaviour territory and all
> answers are fine in that case.
 
Hi Jakub

Thanks for your quick reply.

POSIX does not define any errno values for time(), but nevertheless 
says:

    Upon successful completion, time( ) shall return the value of 
    time. Otherwise, (time_t)−1 shall be returned.
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

In my book, that means that time() should reasonably return -1
here.

The POSIX.1 "No errors are defined" means

    that error values returned by a function or stored into a 
    variable accessed through the symbol errno, if any, depend 
    on the implementation.

This does not (in my reading) mean that no error indication 
(i.e., -1 in this case) should be returned.

Note also that glibc is thwarting the underlying system call, which
does actually return -1 for this case (as my program demonstrates).

Cheers,

Michael



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[Bug libc/1952] time() returns incorrect value when given bad address

[drepper at redhat dot com]

------- Additional Comments From drepper at redhat dot com  2005-12-20 07:50 -------
I've added a new implementation which will simply crash for all invalid pointers.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


http://sourceware.org/bugzilla/show_bug.cgi?id=1952

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[Bug libc/1952] time() returns incorrect value when given bad address

[michael dot kerrisk at gmx dot net]

------- Additional Comments From michael dot kerrisk at gmx dot net  2005-12-20 08:18 -------
Subject: Re:  time() returns incorrect value when given bad address

> 
> ------- Additional Comments From drepper at redhat dot com  2005-12-20
> 07:50 ------- 
> I've added a new implementation which will simply crash for
> all invalid pointers.

Good!  Thanks.



-- 


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