[PATCH 1/2] tracing: Fix possible NULL pointer dereferences

[PATCH 1/2] tracing: Fix possible NULL pointer dereferences

[Namhyung Kim]

From: Namhyung Kim <namhyung.kim@lge.com>

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().

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 include/linux/ftrace.h     |  2 +-
 kernel/trace/ftrace.c      | 10 +++++-----
 kernel/trace/trace_stack.c |  2 +-
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 832422d706f4..c7687d8c0b30 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -396,7 +396,7 @@ ssize_t ftrace_filter_write(struct file *file, const char __user *ubuf,
 			    size_t cnt, loff_t *ppos);
 ssize_t ftrace_notrace_write(struct file *file, const char __user *ubuf,
 			     size_t cnt, loff_t *ppos);
-loff_t ftrace_regex_lseek(struct file *file, loff_t offset, int whence);
+loff_t ftrace_filter_lseek(struct file *file, loff_t offset, int whence);
 int ftrace_regex_release(struct inode *inode, struct file *file);
 
 void __init
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 03953fbd1b2a..be2bcb7ab2f7 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2688,7 +2688,7 @@ ftrace_notrace_open(struct inode *inode, struct file *file)
 }
 
 loff_t
-ftrace_regex_lseek(struct file *file, loff_t offset, int whence)
+ftrace_filter_lseek(struct file *file, loff_t offset, int whence)
 {
 	loff_t ret;
 
@@ -3613,7 +3613,7 @@ static const struct file_operations ftrace_filter_fops = {
 	.open = ftrace_filter_open,
 	.read = seq_read,
 	.write = ftrace_filter_write,
-	.llseek = ftrace_regex_lseek,
+	.llseek = ftrace_filter_lseek,
 	.release = ftrace_regex_release,
 };
 
@@ -3621,7 +3621,7 @@ static const struct file_operations ftrace_notrace_fops = {
 	.open = ftrace_notrace_open,
 	.read = seq_read,
 	.write = ftrace_notrace_write,
-	.llseek = ftrace_regex_lseek,
+	.llseek = ftrace_filter_lseek,
 	.release = ftrace_regex_release,
 };
 
@@ -3826,8 +3826,8 @@ static const struct file_operations ftrace_graph_fops = {
 	.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 */
 
@@ -4481,7 +4481,7 @@ static const struct file_operations ftrace_pid_fops = {
 	.open		= ftrace_pid_open,
 	.write		= ftrace_pid_write,
 	.read		= seq_read,
-	.llseek		= seq_lseek,
+	.llseek		= ftrace_filter_lseek,
 	.release	= ftrace_pid_release,
 };
 
diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 8c3f37e2dc43..b20428c5efe2 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -382,7 +382,7 @@ static const struct file_operations stack_trace_filter_fops = {
 	.open = stack_trace_filter_open,
 	.read = seq_read,
 	.write = ftrace_filter_write,
-	.llseek = ftrace_regex_lseek,
+	.llseek = ftrace_filter_lseek,
 	.release = ftrace_regex_release,
 };
 
-- 
1.7.11.7

[PATCH 2/2] tracing: Reset ftrace_graph_filter_enabled if count is zero

[Namhyung Kim]

From: Namhyung Kim <namhyung.kim@lge.com>

The ftrace_graph_count can be decreased with a "!" pattern, so that
the enabled flag should be updated too.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 kernel/trace/ftrace.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index be2bcb7ab2f7..3b5ef16692c5 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3779,7 +3779,11 @@ out:
 	if (fail)
 		return -EINVAL;
 
-	ftrace_graph_filter_enabled = 1;
+	if (*idx)
+		ftrace_graph_filter_enabled = 1;
+	else
+		ftrace_graph_filter_enabled = 0;
+
 	return 0;
 }
 
-- 
1.7.11.7

[PATCH v2 2/2] tracing: Reset ftrace_graph_filter_enabled if count is zero

[Namhyung Kim]

From: Namhyung Kim <namhyung.kim@lge.com>

The ftrace_graph_count can be decreased with a "!" pattern, so that
the enabled flag should be updated too.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 kernel/trace/ftrace.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index be2bcb7ab2f7..daf8df20b764 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3779,7 +3779,8 @@ out:
 	if (fail)
 		return -EINVAL;
 
-	ftrace_graph_filter_enabled = 1;
+	ftrace_graph_filter_enabled = !!(*idx);
+
 	return 0;
 }
 
-- 
1.7.11.7

Re: [PATCH v2 2/2] tracing: Reset ftrace_graph_filter_enabled if count is zero

[Steven Rostedt]

On Thu, 2013-04-11 at 16:01 +0900, Namhyung Kim wrote:
> From: Namhyung Kim <namhyung.kim@lge.com>
> 
> The ftrace_graph_count can be decreased with a "!" pattern, so that
> the enabled flag should be updated too.

Thanks!

Once again I'll push patch 1 to 3.9 and stable as that's a nasty bug.

But this patch isn't that big of a deal, and as we are in the later
-rc's I'll label it with stable and add it to the 3.10 queue.

Thanks,

-- Steve

> 
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> ---
>  kernel/trace/ftrace.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index be2bcb7ab2f7..daf8df20b764 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -3779,7 +3779,8 @@ out:
>  	if (fail)
>  		return -EINVAL;
>  
> -	ftrace_graph_filter_enabled = 1;
> +	ftrace_graph_filter_enabled = !!(*idx);
> +
>  	return 0;
>  }
>  

[PATCH 0/2] [GIT PULL][v3.9-rc7] tracing: Another fix by Namhyung

[Steven Rostedt]

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Linus,

Namhyung found and fixed another nasty bug, where you can crash the
kernel with: echo 1234 | tee -a /sys/kernel/debug/tracing/set_ftrace_pid

Luckily, only root has permissions to write to that file.

I also added a fix on top of Namhyung's as his patch added a reference
outside of the DYNAMIC_FTRACE to a function that is only defined
in DYNAMIC_FTRACE. This fixes compiling with FUNCTION_TRACING and
without DYNAMIC_FTRACE (although I don't know who does that anymore).

-- Steve

Please pull the latest trace-fixes-v3.9-rc-v3 tree, which can be found at:

  git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
trace-fixes-v3.9-rc-v3

Head SHA1: 0e1bb617b40659414778baf3203c2ea0dcda1ca7


Namhyung Kim (1):
      tracing: Fix possible NULL pointer dereferences

Steven Rostedt (Red Hat) (1):
      ftrace: Move ftrace_filter_lseek out of CONFIG_DYNAMIC_FTRACE section

----
 include/linux/ftrace.h     |    3 ++-
 kernel/trace/ftrace.c      |   36 ++++++++++++++++++------------------
 kernel/trace/trace_stack.c |    2 +-
 3 files changed, 21 insertions(+), 20 deletions(-)

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[PATCH 1/2] tracing: Fix possible NULL pointer dereferences

[Steven Rostedt]

[-- Attachment #1: Type: text/plain, Size: 3750 bytes --]

From: Namhyung Kim <namhyung.kim@lge.com>

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     |    2 +-
 kernel/trace/ftrace.c      |   10 +++++-----
 kernel/trace/trace_stack.c |    2 +-
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 167abf9..eb3ce32 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -396,7 +396,7 @@ ssize_t ftrace_filter_write(struct file *file, const char __user *ubuf,
 			    size_t cnt, loff_t *ppos);
 ssize_t ftrace_notrace_write(struct file *file, const char __user *ubuf,
 			     size_t cnt, loff_t *ppos);
-loff_t ftrace_regex_lseek(struct file *file, loff_t offset, int whence);
+loff_t ftrace_filter_lseek(struct file *file, loff_t offset, int whence);
 int ftrace_regex_release(struct inode *inode, struct file *file);
 
 void __init
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 926ebfb..affc35d 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2697,7 +2697,7 @@ ftrace_notrace_open(struct inode *inode, struct file *file)
 }
 
 loff_t
-ftrace_regex_lseek(struct file *file, loff_t offset, int whence)
+ftrace_filter_lseek(struct file *file, loff_t offset, int whence)
 {
 	loff_t ret;
 
@@ -3570,7 +3570,7 @@ static const struct file_operations ftrace_filter_fops = {
 	.open = ftrace_filter_open,
 	.read = seq_read,
 	.write = ftrace_filter_write,
-	.llseek = ftrace_regex_lseek,
+	.llseek = ftrace_filter_lseek,
 	.release = ftrace_regex_release,
 };
 
@@ -3578,7 +3578,7 @@ static const struct file_operations ftrace_notrace_fops = {
 	.open = ftrace_notrace_open,
 	.read = seq_read,
 	.write = ftrace_notrace_write,
-	.llseek = ftrace_regex_lseek,
+	.llseek = ftrace_filter_lseek,
 	.release = ftrace_regex_release,
 };
 
@@ -3783,8 +3783,8 @@ static const struct file_operations ftrace_graph_fops = {
 	.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 */
 
@@ -4439,7 +4439,7 @@ static const struct file_operations ftrace_pid_fops = {
 	.open		= ftrace_pid_open,
 	.write		= ftrace_pid_write,
 	.read		= seq_read,
-	.llseek		= seq_lseek,
+	.llseek		= ftrace_filter_lseek,
 	.release	= ftrace_pid_release,
 };
 
diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 42ca822..83a8b5b 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -322,7 +322,7 @@ static const struct file_operations stack_trace_filter_fops = {
 	.open = stack_trace_filter_open,
 	.read = seq_read,
 	.write = ftrace_filter_write,
-	.llseek = ftrace_regex_lseek,
+	.llseek = ftrace_filter_lseek,
 	.release = ftrace_regex_release,
 };
 
-- 
1.7.10.4



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