tracing: Fix possible NULL pointer dereferences
authorNamhyung Kim <namhyung.kim@lge.com>
Thu, 11 Apr 2013 06:55:01 +0000 (15:55 +0900)
committerSteven Rostedt <rostedt@goodmis.org>
Fri, 12 Apr 2013 18:43:34 +0000 (14:43 -0400)
commit6a76f8c0ab19f215af2a3442870eeb5f0e81998d
tree551f1c13779323e06b8ef906192ba7a5d87aa7b6
parent83e03b3fe4daffdebbb42151d5410d730ae50bd1
tracing: Fix possible NULL pointer dereferences

Currently set_ftrace_pid and set_graph_function files use seq_lseek
for their fops.  However seq_open() is called only for FMODE_READ in
the fops->open() so that if an user tries to seek one of those file
when she open it for writing, it sees NULL seq_file and then panic.

It can be easily reproduced with following command:

  $ cd /sys/kernel/debug/tracing
  $ echo 1234 | sudo tee -a set_ftrace_pid

In this example, GNU coreutils' tee opens the file with fopen(, "a")
and then the fopen() internally calls lseek().

Link: http://lkml.kernel.org/r/1365663302-2170-1-git-send-email-namhyung@kernel.org

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: stable@vger.kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
include/linux/ftrace.h
kernel/trace/ftrace.c
kernel/trace/trace_stack.c