From: igor@9lab.org
To: 9front@9front.org
Cc: igor@9lab.org, ori@eigenstate.org
Subject: Re: [9front] upas/Mail: fix multiple suicides (use after free, double free) in mbox.c (patch)
Date: Mon, 12 Apr 2021 14:49:36 +0200 [thread overview]
Message-ID: <6C9435B0EAB3ECBB65041EE29A4AA82D@9lab.org> (raw)
In-Reply-To: <97FDE9A5306132622D1D4F91D0453FA9@eigenstate.org>
Quoth ori@eigenstate.org:
> Quoth igor@9lab.org:
> > Below is a patch (inline) that fixes two variants of a suicide (use
> > after free, double free) in Mail/mbox.c on latest 9front 'Mit
> > Fruchtgeschmack' (explanation with reproducible test instructions
> > below) when messages are deleted/moved in bulk:
> >
> > <patch>
> > diff -r 4dfbef4fa4ac sys/src/cmd/upas/Mail/mbox.c
> > --- a/sys/src/cmd/upas/Mail/mbox.c Sat Apr 03 19:32:47 2021 +0200
> > +++ b/sys/src/cmd/upas/Mail/mbox.c Fri Apr 09 02:54:10 2021 +0200
> > @@ -675,10 +675,11 @@
> > static void
> > mbflush(char **, int)
> > {
> > - int i, j, ln, fd;
> > + int i, j, ln, fd, nmesg;
> > char *path;
> > Mesg *m, *p;
> >
> > + nmesg = mbox.nmesg;
> > path = estrjoin(maildir, "/ctl", nil);
> > fd = open(path, OWRITE);
> > free(path);
> > @@ -708,11 +709,13 @@
> > mbredraw(m->child[j], 1, 1);
> > }
> >
> > - for(i = 0, j = 0; i < mbox.nmesg; i++){
> > + for(i = 0, j = 0; i < nmesg; i++){
> > m = mbox.mesg[i];
> > - if((m->state & Szap) != 0)
> > + if((m->state & Szap) != 0){
> > mesgfree(m);
> > - else
> > + mbox.mesg[i] = nil;
> > + mbox.nmesg--;
> > + }else
> > mbox.mesg[j++] = m;
> > }
>
> I think I prefer this patch:
>
> diff -r 503c5ef2d2b5 sys/src/cmd/upas/Mail/mbox.c
> --- a/sys/src/cmd/upas/Mail/mbox.c Sun Apr 11 20:20:41 2021 +0200
> +++ b/sys/src/cmd/upas/Mail/mbox.c Sun Apr 11 19:58:55 2021 -0700
> @@ -715,6 +715,7 @@
> else
> mbox.mesg[j++] = m;
> }
> + mbox.nmesg = j;
>
> close(fd);
> fprint(mbox.ctl, "clean\n");
>
I agree, this is simpler.
Can we set the slot of the deleted message to nil as well to avoid
keeping around pointers to already freed memory?
The following expresses this in a patch:
<snip>
diff -r 4dfbef4fa4ac sys/src/cmd/upas/Mail/mbox.c
--- a/sys/src/cmd/upas/Mail/mbox.c Sat Apr 03 19:32:47 2021 +0200
+++ b/sys/src/cmd/upas/Mail/mbox.c Mon Apr 12 14:35:54 2021 +0200
@@ -710,12 +710,14 @@
for(i = 0, j = 0; i < mbox.nmesg; i++){
m = mbox.mesg[i];
- if((m->state & Szap) != 0)
+ if((m->state & Szap) != 0){
mesgfree(m);
- else
+ mbox.mesg[i] = nil;
+ }else
mbox.mesg[j++] = m;
}
-
+ mbox.nmesg = j;
+
close(fd);
fprint(mbox.ctl, "clean\n");
}
</snip>
This is an optional request, if you disagree with it I am fine
with your proposal.
next prev parent reply other threads:[~2021-04-12 14:05 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-11 20:19 igor
2021-04-12 2:59 ` ori
2021-04-12 12:49 ` igor [this message]
2021-04-12 15:51 ` cinap_lenrek
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