[Ocfs2-tools-devel] [PATCH V1] mount.ocfs2: Fix double free problems when remounting a device

[Shichangkuo]

Hi Joseph,
Thanks for your reply.

> -----Original Message-----
> From: Joseph Qi [mailto:jiangqi903 at gmail.com]
> Sent: Monday, February 12, 2018 9:05 AM
> To: shichangkuo (Cloud); Ocfs2-tools-devel at oss.oracle.com
> Subject: Re: [Ocfs2-tools-devel] [PATCH V1] mount.ocfs2: Fix double free
> problems when remounting a device
>
>
>
> On 18/2/11 20:39, Shichangkuo wrote:
> > From 60985d3705d401427c5db4116716fc5bc5223662 Mon Sep 17
> 00:00:00 2001
> > From: shichangkuo <shi.changkuo at h3c.com>
> > Date: Wed, 7 Feb 2018 17:25:08 +0800
> > Subject: [PATCH] mount.ocfs2: Fix double free problems when remounting
> > a  device
> >
> The above should be eliminated in your patch body.
>
OK, I will revise it in next version.

> > When remounting a device, the issue happens:
> > ~# mount -o remount,rw /vms/share
> > *** Error in `/sbin/mount.ocfs2': double free or corruption (!prev):
> > 0x0000000000b305a0
> > *** Aborted
> >
> > When updating the mtab, we should free the old mnt_opts, and duplicate
> > a new one from instead->mnt_opts.
> >
> > Signed-off-by: shichangkuo <shi.changkuo at h3c.com>
> > ---
> >  mount.ocfs2/fstab.c |    3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/mount.ocfs2/fstab.c b/mount.ocfs2/fstab.c index
> > d3fc617..59cd369 100644
> > --- a/mount.ocfs2/fstab.c
> > +++ b/mount.ocfs2/fstab.c
> > @@ -612,7 +612,8 @@ update_mtab (const char *dir, struct my_mntent
> *instead) {
> >                         }
> >                 } else {
> >                         /* A remount */
> > -                       mc->m.mnt_opts = instead->mnt_opts;
> > +                       my_free(mc->m.mnt_opts);
> Why we have to free here?
>
mc-> mnt_opts was malloced in read_mntentchn, so we have to free it, otherwise it could cause memory leak.
If we change pointer mc-> mnt_opts directly, it will have double free, therefore we should duplicate it from instead->mnt_opts.

Thanks,
Changkuo

> Thanks,
> Joseph
>
> > +                       mc->m.mnt_opts =
> xstrdup(instead->mnt_opts);
> >                 }
> >         } else if (instead) {
> >                 /* not found, add a new entry */
> > --
> > 1.7.9.5
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