From a68c5a52d5a1e42830b0563d7c5421e0153ae636 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 29 May 2019 14:37:24 +0200 Subject: [PATCH] perf/core: Fix perf_sample_regs_user() mm check [ 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 Reported-by: Young Xiao <92siuyang@gmail.com> Signed-off-by: Peter Zijlstra (Intel) Acked-by: Will Deacon Cc: Arnaldo Carvalho de Melo Cc: Frederic Weisbecker Cc: Jiri Olsa Cc: Linus Torvalds Cc: Michael Ellerman Cc: Naveen N. Rao Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Fixes: 4018994f3d87 ("perf: Add ability to attach user level registers dump to sample") Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin --- 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 580616e6fcee..3d4eb6f840eb 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -5630,7 +5630,7 @@ 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; -- 2.20.1