From: Florian Weimer <fweimer@redhat.com>
To: DJ Delorie <dj@redhat.com>
Cc: libc-alpha@sourceware.org
Subject: Re: [PATCH] malloc: Check for large bin list corruption when inserting unsorted chunk
Date: Wed, 06 Mar 2019 13:09:46 +0100 [thread overview]
Message-ID: <87h8cgcigl.fsf@oldenburg2.str.redhat.com> (raw)
In-Reply-To: <xnmumoa9tf.fsf@greed.delorie.com> (DJ Delorie's message of "Thu, 21 Feb 2019 20:30:52 -0500")
* DJ Delorie:
> Adam Maris <amaris@redhat.com> writes:
>> {
>> victim->fd_nextsize = fwd;
>> victim->bk_nextsize = fwd->bk_nextsize;
>> + if (__glibc_unlikely (fwd->bk_nextsize->fd_nextsize != fwd))
>> + malloc_printerr ("malloc(): largebin double linked list corrupted (nextsize)");
>
> At this point, the size of the chunk matches neither the previous nor
> next chunks; we're creating a new "unique size" sub-head. So, both fd
> and fd_nextsize should point to the next (fwd) chunk. We've hooked in
> our new chunk but haven't yet fixed up the existing chunks, so this test
> verifies that the links between the next chunk (fwd, which is a
> start-of-size chunk) and the previous start-of-size chunk are still
> cyclic. Ok.
>
>> fwd->bk_nextsize = victim;
>> victim->bk_nextsize->fd_nextsize = victim;
>> }
>> bck = fwd->bk;
>> + if (bck->fd != fwd)
>> + malloc_printerr ("malloc(): largebin double linked list corrupted (bk)");
>
> At this point the newly inserted chunk may be a start-of-size chunk, or
> a second-in-size chunk; either way, we've not yet linked it into the
> fd-bk chain, so we can verify that the fwd->bk->fd is still cyclic. Ok.
>
> So, looks correct to me.
> Reviewed-by: DJ Delorie <dj@redhat.com>
I agree with this analysis.
Adam's submission is no longer covered by the Red Hat copyright
assignment, though, but I believe we can still accept it because it was
submitted under the assignment, and it is a small change anyway.
Thanks,
Florian
next prev parent reply other threads:[~2019-03-06 12:09 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-12 16:13 [PATCH] malloc: Check for large bin list corruption when inserting unsorted chunk Adam Maris
2019-02-12 16:34 ` Adam Maris
2019-02-21 10:40 ` Adam Maris
2019-02-22 1:30 ` DJ Delorie
2019-03-06 12:09 ` Florian Weimer [this message]
2019-03-14 20:56 ` DJ Delorie
2019-05-15 15:50 ` Andreas Schwab
2019-05-15 16:12 ` DJ Delorie
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