3.16.75-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Peter Zijlstra <[email protected]> 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 <[email protected]> Reported-by: Young Xiao <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Acked-by: Will Deacon <[email protected]> Cc: Arnaldo Carvalho de Melo <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: Jiri Olsa <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Michael Ellerman <[email protected]> Cc: Naveen N. Rao <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Stephane Eranian <[email protected]> Cc: Thomas Gleixner <[email protected]> Fixes: 4018994f3d87 ("perf: Add ability to attach user level registers dump to sample") Signed-off-by: Ingo Molnar <[email protected]> [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings <[email protected]> --- 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;
