lkml.org 
[lkml]   [2018]   [Sep]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4.18 138/235] perf/core: Force USER_DS when recording user stack data
Date
4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Yabin Cui <yabinc@google.com>

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 <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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
kernel/events/core.c | 4 ++++
1 file changed, 4 insertions(+)

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5948,6 +5948,7 @@ perf_output_sample_ustack(struct perf_ou
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_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);

\
 
 \ /
  Last update: 2018-09-24 14:39    [W:0.891 / U:2.540 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site