Wireshark mailing list archives
Re: Canaries in Wmem
From: Jeff Morriss <jeff.morriss.ws () gmail com>
Date: Fri, 21 Dec 2012 10:44:04 -0500
Jeff Morriss wrote:
Evan Huus wrote:They've been on my to-do list for a while, as emem provides them. However, I've never personally used emem's canaries, and I've never actually heard of or seen anyone else using them. Are they actually useful anymore, or has Moore's law made valgrind the better tool in all situations?Well, the canaries have helped us find (and fix) a *lot* of bugs over the years. I have this vague memory of a time when most of the fuzz failures complained of canary corruption but maybe that's an exaggeration. Hopefully the lack of canary corruption these days is a sign of improvement. :-)I think they're still useful for the automated fuzz testing because we get a fuzz failure when the fuzz-bot finds a corrupted canary. Valgrind is useful to let us humans *find* the memory corruption, but unless we're at a point where the fuzz-bot can run Valgrind instead of its normal testing, I don't think we should give up the canaries.If we do believe they're still useful, now's the time to suggest cool new features for them etc. Would they be used more if could be enabled with an environment variable instead of a compile flag? Are the mprotected pages actually useful, or are 99% of things caught by the simpler canaries?There are environment variables to enable/disable the canaries: that's what allows the Valgrind script to actually work. :-)
Of course as soon as I hit "Send" I realized I was thinking of something different: the environment variables which control how the allocations are done, not whether or not there are canaries.
But there are still environment variables for the canaries: in particular, SE canaries are off by default (because they were using a *lot* of memory) but we turn them on while fuzz testing.
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Current thread:
- Canaries in Wmem Evan Huus (Dec 19)
- Re: Canaries in Wmem Jeff Morriss (Dec 21)
- Re: Canaries in Wmem Jeff Morriss (Dec 21)
- Re: Canaries in Wmem Evan Huus (Dec 21)
- Re: Canaries in Wmem Jeff Morriss (Dec 21)
- Re: Canaries in Wmem Evan Huus (Dec 21)
- Re: Canaries in Wmem Jeff Morriss (Dec 21)
- Re: Canaries in Wmem Guy Harris (Dec 21)
- Re: Canaries in Wmem Evan Huus (Dec 21)
- Re: Canaries in Wmem Gerald Combs (Dec 22)
- Re: Canaries in Wmem Evan Huus (Dec 21)