tracing: Fix possible NULL pointer dereferences
authorNamhyung Kim <namhyung.kim@lge.com>
Fri, 7 Jun 2013 09:00:33 +0000 (17:00 +0800)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 13 Jun 2013 16:25:13 +0000 (09:25 -0700)
commitc45fe24c84eb35565a252c4fe2dd851cee22cb3e
treef4f87f69bd948bc2003542affe00e1ae6625dac8
parent24d54932440284584060455a81156f7ca4edff0e
tracing: Fix possible NULL pointer dereferences

commit 6a76f8c0ab19f215af2a3442870eeb5f0e81998d upstream.

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

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
[ lizf: adjust context ]
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernel/trace/ftrace.c