3.16.75-rc1 review patch. If anyone has any objections, please let me know.
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From: Peter Zijlstra peterz@infradead.org
commit 085ebfe937d7a7a5df1729f35a12d6d655fea68c upstream.
perf_sample_regs_user() uses 'current->mm' to test for the presence of userspace, but this is insufficient, consider use_mm().
A better test is: '!(current->flags & PF_KTHREAD)', exec() clears PF_KTHREAD after it sets the new ->mm but before it drops to userspace for the first time.
Possibly obsoletes: bf05fc25f268 ("powerpc/perf: Fix oops when kthread execs user process")
Reported-by: Ravi Bangoria ravi.bangoria@linux.vnet.ibm.com Reported-by: Young Xiao 92siuyang@gmail.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Acked-by: Will Deacon will.deacon@arm.com Cc: Arnaldo Carvalho de Melo acme@redhat.com Cc: Frederic Weisbecker fweisbec@gmail.com Cc: Jiri Olsa jolsa@redhat.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Michael Ellerman mpe@ellerman.id.au Cc: Naveen N. Rao naveen.n.rao@linux.vnet.ibm.com Cc: Peter Zijlstra peterz@infradead.org Cc: Stephane Eranian eranian@google.com Cc: Thomas Gleixner tglx@linutronix.de Fixes: 4018994f3d87 ("perf: Add ability to attach user level registers dump to sample") Signed-off-by: Ingo Molnar mingo@kernel.org [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- kernel/events/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4581,7 +4581,7 @@ static void perf_sample_regs_user(struct struct pt_regs *regs) { if (!user_mode(regs)) { - if (current->mm) + if (!(current->flags & PF_KTHREAD)) regs = task_pt_regs(current); else regs = NULL;