tracing: Fix possible NULL pointer dereferences

From: Li Zefan
Date: Fri Jun 07 2013 - 05:00:33 EST



From: Namhyung Kim <namhyung.kim@xxxxxxx>

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@xxxxxxxxxx

Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung.kim@xxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
[ lizf: adjust context ]
Signed-off-by: Li Zefan <lizefan@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/ftrace.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2300,7 +2300,7 @@ ftrace_notrace_open(struct inode *inode,
}

static loff_t
-ftrace_regex_lseek(struct file *file, loff_t offset, int origin)
+ftrace_filter_lseek(struct file *file, loff_t offset, int origin)
{
loff_t ret;

@@ -3118,7 +3118,7 @@ static const struct file_operations ftra
.open = ftrace_filter_open,
.read = seq_read,
.write = ftrace_filter_write,
- .llseek = ftrace_regex_lseek,
+ .llseek = ftrace_filter_lseek,
.release = ftrace_regex_release,
};

@@ -3126,7 +3126,7 @@ static const struct file_operations ftra
.open = ftrace_notrace_open,
.read = seq_read,
.write = ftrace_notrace_write,
- .llseek = ftrace_regex_lseek,
+ .llseek = ftrace_filter_lseek,
.release = ftrace_regex_release,
};

@@ -3335,8 +3335,8 @@ static const struct file_operations ftra
.open = ftrace_graph_open,
.read = seq_read,
.write = ftrace_graph_write,
+ .llseek = ftrace_filter_lseek,
.release = ftrace_graph_release,
- .llseek = seq_lseek,
};
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

@@ -3822,7 +3822,7 @@ static const struct file_operations ftra
.open = ftrace_pid_open,
.write = ftrace_pid_write,
.read = seq_read,
- .llseek = seq_lseek,
+ .llseek = ftrace_filter_lseek,
.release = ftrace_pid_release,
};



Patches currently in stable-queue which might be from lizefan@xxxxxxxxxx are

queue-3.0/tracing-fix-possible-null-pointer-dereferences.patch
queue-3.0/ftrace-move-ftrace_filter_lseek-out-of-config_dynamic_ftrace-section.patch
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