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>

3 files changed, 12 insertions, 0 deletions

diff --git a/drivers/oprofile/cpu_buffer.c b/drivers/oprofile/cpu_buffer.c
index a83c3db7d18f..c93d3d2640ab 100644
--- a/drivers/oprofile/cpu_buffer.c
+++ b/drivers/oprofile/cpu_buffer.c
@@ -64,6 +64,8 @@ int alloc_cpu_buffers(void)
                 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 @@ static int log_sample(struct oprofile_cpu_buffer * cpu_buf, unsigned long pc,
 
         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 49900d9e3235..c66c025abe75 100644
--- a/drivers/oprofile/cpu_buffer.h
+++ b/drivers/oprofile/cpu_buffer.h
@@ -42,6 +42,7 @@ struct oprofile_cpu_buffer {
         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 f0acb661c253..d1f6d776e9e4 100644
--- a/drivers/oprofile/oprofile_stats.c
+++ b/drivers/oprofile/oprofile_stats.c
@@ -26,6 +26,8 @@ void oprofile_reset_stats(void)
                 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 @@ void oprofile_create_stats_files(struct super_block * sb, struct dentry * root)
                         &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",