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>

1 files changed, 4 insertions, 0 deletions

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",