releases/4.9.129/perf-core-force-user_ds-when-recording-user-stack-data.patch

   1 From 02e184476eff848273826c1d6617bb37e5bcc7ad Mon Sep 17 00:00:00 2001
   2 From: Yabin Cui <yabinc@google.com>
   3 Date: Thu, 23 Aug 2018 15:59:35 -0700
   4 Subject: perf/core: Force USER_DS when recording user stack data
   5
   6 From: Yabin Cui <yabinc@google.com>
   7
   8 commit 02e184476eff848273826c1d6617bb37e5bcc7ad upstream.
   9
  10 Perf can record user stack data in response to a synchronous request, such
  11 as a tracepoint firing. If this happens under set_fs(KERNEL_DS), then we
  12 end up reading user stack data using __copy_from_user_inatomic() under
  13 set_fs(KERNEL_DS). I think this conflicts with the intention of using
  14 set_fs(KERNEL_DS). And it is explicitly forbidden by hardware on ARM64
  15 when both CONFIG_ARM64_UAO and CONFIG_ARM64_PAN are used.
  16
  17 So fix this by forcing USER_DS when recording user stack data.
  18
  19 Signed-off-by: Yabin Cui <yabinc@google.com>
  20 Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
  21 Cc: <stable@vger.kernel.org>
  22 Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
  23 Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
  24 Cc: Jiri Olsa <jolsa@redhat.com>
  25 Cc: Linus Torvalds <torvalds@linux-foundation.org>
  26 Cc: Namhyung Kim <namhyung@kernel.org>
  27 Cc: Peter Zijlstra <peterz@infradead.org>
  28 Cc: Thomas Gleixner <tglx@linutronix.de>
  29 Fixes: 88b0193d9418 ("perf/callchain: Force USER_DS when invoking perf_callchain_user()")
  30 Link: http://lkml.kernel.org/r/20180823225935.27035-1-yabinc@google.com
  31 Signed-off-by: Ingo Molnar <mingo@kernel.org>
  32 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  33
  34 ---
  35  kernel/events/core.c |    4 ++++
  36  1 file changed, 4 insertions(+)
  37
  38 --- a/kernel/events/core.c
  39 +++ b/kernel/events/core.c
  40 @@ -5563,6 +5563,7 @@ perf_output_sample_ustack(struct perf_ou
  41                 unsigned long sp;
  42                 unsigned int rem;
  43                 u64 dyn_size;
  44 +               mm_segment_t fs;
  45
  46                 /*
  47                  * We dump:
  48 @@ -5580,7 +5581,10 @@ perf_output_sample_ustack(struct perf_ou
  49
  50                 /* Data. */
  51                 sp = perf_user_stack_pointer(regs);
  52 +               fs = get_fs();
  53 +               set_fs(USER_DS);
  54                 rem = __output_copy_user(handle, (void *) sp, dump_size);
  55 +               set_fs(fs);
  56                 dyn_size = dump_size - rem;
  57
  58                 perf_output_skip(handle, rem);