Commit c026b359 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar

x86, mm, perf: Allow recursive faults from interrupts

Waiman managed to trigger a PMI while in a emulate_vsyscall() fault,
the PMI in turn managed to trigger a fault while obtaining a stack
trace. This triggered the sig_on_uaccess_error recursive fault logic
and killed the process dead.

Fix this by explicitly excluding interrupts from the recursive fault
logic.
Reported-and-Tested-by: default avatarWaiman Long <waiman.long@hp.com>
Fixes: e00b12e6 ("perf/x86: Further optimize copy_from_user_nmi()")
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20140110200603.GJ7572@laptop.programming.kicks-ass.netSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 85ce70fd
......@@ -641,6 +641,20 @@ no_context(struct pt_regs *regs, unsigned long error_code,
/* Are we prepared to handle this kernel fault? */
if (fixup_exception(regs)) {
/*
* Any interrupt that takes a fault gets the fixup. This makes
* the below recursive fault logic only apply to a faults from
* task context.
*/
if (in_interrupt())
return;
/*
* Per the above we're !in_interrupt(), aka. task context.
*
* In this case we need to make sure we're not recursively
* faulting through the emulate_vsyscall() logic.
*/
if (current_thread_info()->sig_on_uaccess_error && signal) {
tsk->thread.trap_nr = X86_TRAP_PF;
tsk->thread.error_code = error_code | PF_USER;
......@@ -649,6 +663,10 @@ no_context(struct pt_regs *regs, unsigned long error_code,
/* XXX: hwpoison faults will set the wrong code. */
force_sig_info_fault(signal, si_code, address, tsk, 0);
}
/*
* Barring that, we can do the fixup and be happy.
*/
return;
}
......
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