oProfile: oops when profile_pc() returns ~0LU
Instruction pointer returned by profile_pc() can be a random value. This
break the assumption than we can safely set struct op_sample.eip field to a
magic value to signal to the per-cpu buffer reader side special event like
task switch ending up in a segfault in get_task_mm() when profile_pc()
return ~0UL. Fixed by sanitizing the sampled eip and reject/log invalid
eip.
Problem reported by Sami Farin, patch tested by him.
Signed-off-by: Philippe Elie <phil.el@wanadoo.fr>
Tested-by: Sami Farin <safari-kernel@safari.iki.fi>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/oprofile/cpu_buffer.c b/drivers/oprofile/cpu_buffer.c
index a83c3db..c93d3d2 100644
--- a/drivers/oprofile/cpu_buffer.c
+++ b/drivers/oprofile/cpu_buffer.c
@@ -64,6 +64,8 @@
b->head_pos = 0;
b->sample_received = 0;
b->sample_lost_overflow = 0;
+ b->backtrace_aborted = 0;
+ b->sample_invalid_eip = 0;
b->cpu = i;
INIT_DELAYED_WORK(&b->work, wq_sync_buffer);
}
@@ -175,6 +177,11 @@
cpu_buf->sample_received++;
+ if (pc == ESCAPE_CODE) {
+ cpu_buf->sample_invalid_eip++;
+ return 0;
+ }
+
if (nr_available_slots(cpu_buf) < 3) {
cpu_buf->sample_lost_overflow++;
return 0;
diff --git a/drivers/oprofile/cpu_buffer.h b/drivers/oprofile/cpu_buffer.h
index 49900d9..c66c025 100644
--- a/drivers/oprofile/cpu_buffer.h
+++ b/drivers/oprofile/cpu_buffer.h
@@ -42,6 +42,7 @@
unsigned long sample_received;
unsigned long sample_lost_overflow;
unsigned long backtrace_aborted;
+ unsigned long sample_invalid_eip;
int cpu;
struct delayed_work work;
} ____cacheline_aligned;
diff --git a/drivers/oprofile/oprofile_stats.c b/drivers/oprofile/oprofile_stats.c
index f0acb66..d1f6d77 100644
--- a/drivers/oprofile/oprofile_stats.c
+++ b/drivers/oprofile/oprofile_stats.c
@@ -26,6 +26,8 @@
cpu_buf = &cpu_buffer[i];
cpu_buf->sample_received = 0;
cpu_buf->sample_lost_overflow = 0;
+ cpu_buf->backtrace_aborted = 0;
+ cpu_buf->sample_invalid_eip = 0;
}
atomic_set(&oprofile_stats.sample_lost_no_mm, 0);
@@ -61,6 +63,8 @@
&cpu_buf->sample_lost_overflow);
oprofilefs_create_ro_ulong(sb, cpudir, "backtrace_aborted",
&cpu_buf->backtrace_aborted);
+ oprofilefs_create_ro_ulong(sb, cpudir, "sample_invalid_eip",
+ &cpu_buf->sample_invalid_eip);
}
oprofilefs_create_ro_atomic(sb, dir, "sample_lost_no_mm",