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SubjectRe: [PATCH v8 5/6] x86/signal: Detect and prevent an alternate signal stack overflow
Date
On May 11, 2021, at 11:36, Borislav Petkov <bp@alien8.de> wrote:
>
> I clumsily tried to register a SIGSEGV handler with
>
> act.sa_sigaction = my_sigsegv;
> sigaction(SIGSEGV, &act, NULL);
>
> but that doesn't fire - task gets killed. Maybe I'm doing it wrong.

Since the altstack is already overflowed, perhaps set the flag like this -- not
using it to get the handler:

act.sa_sigaction = my_sigsegv;
+ act.sa_flags = SA_SIGINFO;
sigaction(SIGSEGV, &act, NULL);

FWIW, I think this is just a workaround for this case; in practice, altstack is
rather a backup for normal stack corruption.

Thanks,
Chang

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