From: Peter Zijlstra peterz@infradead.org
[ Upstream commit 085ebfe937d7a7a5df1729f35a12d6d655fea68c ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/events/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c index dc7dead2d2cc..f33bd0a89391 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -5913,7 +5913,7 @@ static void perf_sample_regs_user(struct perf_regs *regs_user, if (user_mode(regs)) { regs_user->abi = perf_reg_abi(current); regs_user->regs = regs; - } else if (current->mm) { + } else if (!(current->flags & PF_KTHREAD)) { perf_get_regs_user(regs_user, regs, regs_user_copy); } else { regs_user->abi = PERF_SAMPLE_REGS_ABI_NONE;