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[Bug malloc/12140] mallopt(M_PERTURB) free() anomaly
- From: "siddhesh at redhat dot com" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sources dot redhat dot com
- Date: Wed, 17 Oct 2012 13:02:01 +0000
- Subject: [Bug malloc/12140] mallopt(M_PERTURB) free() anomaly
- Auto-submitted: auto-generated
- References: <bug-12140-131@http.sourceware.org/bugzilla/>
http://sourceware.org/bugzilla/show_bug.cgi?id=12140
--- Comment #6 from Siddhesh Poyarekar <siddhesh at redhat dot com> 2012-10-17 13:02:01 UTC ---
Yes, that's the fun part. The fd and bk pointers are written within the usable
area for a free block - it saves 2*sizeof(void *) per chunk. In any case, a
user should not expect to be able to use them anyway for doing a check similar
to what you did after free, because that is undefined - you could cause a
segfault if the chunk was allocated using mmap.
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