Messages in this thread | | | Date | Mon, 17 Jul 2017 13:04:34 -0500 (CDT) | From | Christopher Lameter <> | Subject | Re: [PATCH 1/1] mm/slub.c: add a naive detection of double free or corruption |
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On Mon, 17 Jul 2017, Matthew Wilcox wrote:
> On Mon, Jul 17, 2017 at 07:45:07PM +0300, Alexander Popov wrote: > > Add an assertion similar to "fasttop" check in GNU C Library allocator: > > an object added to a singly linked freelist should not point to itself. > > That helps to detect some double free errors (e.g. CVE-2017-2636) without > > slub_debug and KASAN. Testing with hackbench doesn't show any noticeable > > performance penalty. > > > { > > + BUG_ON(object == fp); /* naive detection of double free or corruption */ > > *(void **)(object + s->offset) = fp; > > } > > Is BUG() the best response to this situation? If it's a corruption, then > yes, but if we spot a double-free, then surely we should WARN() and return > without doing anything?
The double free debug checking already does the same thing in a more thourough way (this one only checks if the last free was the same address). So its duplicating a check that already exists. However, this one is always on.
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