From: Alexander Shishkin alexander.shishkin@linux.intel.com
[ Upstream commit 36b3db03b4741b8935b68fffc7e69951d8d70a89 ]
Commit:
5e6c3c7b1ec2 ("perf/aux: Fix tracking of auxiliary trace buffer allocation")
tried to guess the correct combination of arithmetic operations that would undo the AUX buffer's mlock accounting, and failed, leaking the bottom part when an allocation needs to be charged partially to both user->locked_vm and mm->pinned_vm, eventually leaving the user with no locked bonus:
$ perf record -e intel_pt//u -m1,128 uname [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.061 MB perf.data ]
$ perf record -e intel_pt//u -m1,128 uname Permission error mapping pages. Consider increasing /proc/sys/kernel/perf_event_mlock_kb, or try again with a smaller value of -m/--mmap_pages. (current value: 1,128)
Fix this by subtracting both locked and pinned counts when AUX buffer is unmapped.
Reported-by: Thomas Richter tmricht@linux.ibm.com Tested-by: Thomas Richter tmricht@linux.ibm.com Signed-off-by: Alexander Shishkin alexander.shishkin@linux.intel.com Acked-by: Peter Zijlstra peterz@infradead.org Cc: Arnaldo Carvalho de Melo acme@redhat.com Cc: Jiri Olsa jolsa@redhat.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Mark Rutland mark.rutland@arm.com Cc: Namhyung Kim namhyung@kernel.org Cc: Stephane Eranian eranian@google.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Vince Weaver vincent.weaver@maine.edu Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/events/core.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c index 00a014670ed0..8f66a4833ded 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -5607,10 +5607,8 @@ static void perf_mmap_close(struct vm_area_struct *vma) perf_pmu_output_stop(event);
/* now it's safe to free the pages */ - if (!rb->aux_mmap_locked) - atomic_long_sub(rb->aux_nr_pages, &mmap_user->locked_vm); - else - atomic64_sub(rb->aux_mmap_locked, &vma->vm_mm->pinned_vm); + atomic_long_sub(rb->aux_nr_pages - rb->aux_mmap_locked, &mmap_user->locked_vm); + atomic64_sub(rb->aux_mmap_locked, &vma->vm_mm->pinned_vm);
/* this has to be the last one */ rb_free_aux(rb);