4.14-stable review patch. If anyone has any objections, please let me know.
------------------ From: Yabin Cui <[email protected]> commit 02e184476eff848273826c1d6617bb37e5bcc7ad upstream. 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 <[email protected]> Acked-by: Peter Zijlstra (Intel) <[email protected]> Cc: <[email protected]> Cc: Alexander Shishkin <[email protected]> Cc: Arnaldo Carvalho de Melo <[email protected]> Cc: Jiri Olsa <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Namhyung Kim <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Fixes: 88b0193d9418 ("perf/callchain: Force USER_DS when invoking perf_callchain_user()") Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- kernel/events/core.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -5700,6 +5700,7 @@ perf_output_sample_ustack(struct perf_ou unsigned long sp; unsigned int rem; u64 dyn_size; + mm_segment_t fs; /* * We dump: @@ -5717,7 +5718,10 @@ perf_output_sample_ustack(struct perf_ou /* 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);
