Commit-ID: c026b3591e4f2a4993df773183704bb31634e0bd
Gitweb: http://git.kernel.org/tip/c026b3591e4f2a4993df773183704bb31634e0bd
Author: Peter Zijlstra <pet...@infradead.org>
AuthorDate: Fri, 10 Jan 2014 21:06:03 +0100
Committer: Ingo Molnar <mi...@kernel.org>
CommitDate: Thu, 16 Jan 2014 09:19:48 +0100
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: Waiman Long <waiman.l...@hp.com>
Fixes: e00b12e64be9 ("perf/x86: Further optimize copy_from_user_nmi()")
Cc: Aswin Chandramouleeswaran <as...@hp.com>
Cc: Scott J Norton <scott.nor...@hp.com>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Andy Lutomirski <l...@amacapital.net>
Cc: Arnaldo Carvalho de Melo <a...@ghostprotocols.net>
Cc: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Peter Zijlstra <pet...@infradead.org>
Link:
http://lkml.kernel.org/r/20140110200603.gj7...@laptop.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---
arch/x86/mm/fault.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 9ff85bb..9d591c8 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -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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