Bad error return after find_vma() in PR_SET_MM code

Bad error return after find_vma() in PR_SET_MM code

[Michael Kerrisk (man-pages)]

[Bother! Resending with corrected subject line (was "[PATCH 1/2]
prctl: Add PR_SET_MM option description")]

Cyrill,

While reviewing your patch to the prctl() manual page, I noticed the
following code in kernel/sys.c::prctl_set_mm():

       if (opt != PR_SET_MM_START_BRK && opt != PR_SET_MM_BRK) {
               /* It must be existing VMA */
               if (!vma || vma->vm_start > addr)
                       goto out;
       }

At this point, the code causes an exit with error set to zero (i.e.,
success). This looks unintended to me. Is the code correct? I suspect
a return of -EFAULT or -ENOMEM is warranted.

Cheers,

Michael

--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface"; http://man7.org/tlpi/

Re: Bad error return after find_vma() in PR_SET_MM code

[KOSAKI Motohiro]

(4/15/12 12:00 AM), Michael Kerrisk (man-pages) wrote:
> [Bother! Resending with corrected subject line (was "[PATCH 1/2]
> prctl: Add PR_SET_MM option description")]
>
> Cyrill,
>
> While reviewing your patch to the prctl() manual page, I noticed the
> following code in kernel/sys.c::prctl_set_mm():
>
>         if (opt != PR_SET_MM_START_BRK&&  opt != PR_SET_MM_BRK) {
>                 /* It must be existing VMA */
>                 if (!vma || vma->vm_start>  addr)
>                         goto out;
>         }
>
> At this point, the code causes an exit with error set to zero (i.e.,
> success). This looks unintended to me. Is the code correct? I suspect
> a return of -EFAULT or -ENOMEM is warranted.

EFAULT please when detecting invalid vma.

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Re: Bad error return after find_vma() in PR_SET_MM code

[Cyrill Gorcunov]

On Tue, Apr 24, 2012 at 11:12:15AM -0400, KOSAKI Motohiro wrote:
> (4/15/12 12:00 AM), Michael Kerrisk (man-pages) wrote:
> >[Bother! Resending with corrected subject line (was "[PATCH 1/2]
> >prctl: Add PR_SET_MM option description")]
> >
> >Cyrill,
> >
> >While reviewing your patch to the prctl() manual page, I noticed the
> >following code in kernel/sys.c::prctl_set_mm():
> >
> >        if (opt != PR_SET_MM_START_BRK&&  opt != PR_SET_MM_BRK) {
> >                /* It must be existing VMA */
> >                if (!vma || vma->vm_start>  addr)
> >                        goto out;
> >        }
> >
> >At this point, the code causes an exit with error set to zero (i.e.,
> >success). This looks unintended to me. Is the code correct? I suspect
> >a return of -EFAULT or -ENOMEM is warranted.
> 
> EFAULT please when detecting invalid vma.

Thanks for reminder, Kosaki! I'll cook a patch asap.

	Cyrill
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