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Date: Thu, 18 Apr 2024 10:25:54 -0700
From: Paul Eggert <eggert@...ucla.edu>
To: libc-coord@...ts.openwall.com, Florian Weimer <fweimer@...hat.com>,
Keith Packard <keithp@...thp.com>
Subject: Re: Preventing re-use of jmp_buf?
On 2024-04-18 03:36, Florian Weimer wrote:
> think it's possible to meet all the preconditions for longjmp and call
> it multiple times after a setjmp call, on the same buffer. Therefore, I
> don't think this would be a conforming or just compatible change.
Quite right.
However, couldn't we catch many instances of the more-important case
where longjmp called with a jmp_buf that's no longer valid? Something
involving a per-thread nonce that's tweaked each time setjmp is called,
and where the nonce's value is stored in both the jmp_buf and in the
setjmp caller's frame, so that longjmp could reliably crash if the nonce
is corrupted. We could do this if fortification is enabled.
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