Messages in this thread Patch in this message | | | Date | Thu, 23 Aug 2018 15:59:35 -0700 | Subject | [PATCH] perf: Force USER_DS when recording user stack data. | From | Yabin Cui <> |
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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> --- kernel/events/core.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/kernel/events/core.c b/kernel/events/core.c index 2a62b96600ad..9bc047421e75 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -5948,6 +5948,7 @@ 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: @@ -5965,7 +5966,10 @@ 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); -- 2.19.0.rc0.228.g281dcd1b4d0-goog
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