Commit-ID: 02e184476eff848273826c1d6617bb37e5bcc7ad Gitweb: https://git.kernel.org/tip/02e184476eff848273826c1d6617bb37e5bcc7ad Author: Yabin Cui yabinc@google.com AuthorDate: Thu, 23 Aug 2018 15:59:35 -0700 Committer: Ingo Molnar mingo@kernel.org CommitDate: Mon, 10 Sep 2018 14:01:46 +0200

perf/core: Force USER_DS when recording user stack data

Perf can record user stack data in response to a synchronous request, such as a tracepoint firing. If this happens under set_fs(KERNEL_DS), then we end up reading user stack data using __copy_from_user_inatomic() under set_fs(KERNEL_DS). I think this conflicts with the intention of using set_fs(KERNEL_DS). And it is explicitly forbidden by hardware on ARM64 when both CONFIG_ARM64_UAO and CONFIG_ARM64_PAN are used.

So fix this by forcing USER_DS when recording user stack data.

Signed-off-by: Yabin Cui yabinc@google.com Acked-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: stable@vger.kernel.org Cc: Alexander Shishkin alexander.shishkin@linux.intel.com Cc: Arnaldo Carvalho de Melo acme@kernel.org Cc: Jiri Olsa jolsa@redhat.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Namhyung Kim namhyung@kernel.org Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Fixes: 88b0193d9418 ("perf/callchain: Force USER_DS when invoking perf_callchain_user()") Link: http://lkml.kernel.org/r/20180823225935.27035-1-yabinc@google.com Signed-off-by: Ingo Molnar mingo@kernel.org --- kernel/events/core.c | 4 ++++ 1 file changed, 4 insertions(+)

diff --git a/kernel/events/core.c b/kernel/events/core.c index abaed4f8bb7f..c80549bf82c6 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -5943,6 +5943,7 @@ perf_output_sample_ustack(struct perf_output_handle *handle, u64 dump_size, unsigned long sp; unsigned int rem; u64 dyn_size; + mm_segment_t fs;

/* * We dump: @@ -5960,7 +5961,10 @@ perf_output_sample_ustack(struct perf_output_handle *handle, u64 dump_size,

/* Data. */ sp = perf_user_stack_pointer(regs); + fs = get_fs(); + set_fs(USER_DS); rem = __output_copy_user(handle, (void *) sp, dump_size); + set_fs(fs); dyn_size = dump_size - rem;

perf_output_skip(handle, rem);