[PATCH 1/2] get_task_comm: use strlcpy instead of strncpy

[PATCH 1/2] get_task_comm: use strlcpy instead of strncpy

[Evgeni Golov]

it's used in set_task_comm too and as far as I understand it should
be used everywhere.

Signed-off-by: Evgeni Golov <sargentd@die-welt.net>
---
 fs/exec.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index e639957..6f1eeb8 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -913,7 +913,7 @@ char *get_task_comm(char *buf, struct task_struct *tsk)
 {
 	/* buf must be at least sizeof(tsk->comm) in size */
 	task_lock(tsk);
-	strncpy(buf, tsk->comm, sizeof(tsk->comm));
+	strlcpy(buf, tsk->comm, sizeof(tsk->comm));
 	task_unlock(tsk);
 	return buf;
 }
-- 
1.6.3.1

[PATCH 2/2] use the TASK_COMM_LEN macro instead of sizeof(tsk->comm)

[Evgeni Golov]

sizeof(tsk->comm) == TASK_COMM_LEN, always, so why not use it?

Signed-off-by: Evgeni Golov <sargentd@die-welt.net>
---
 fs/exec.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index 6f1eeb8..14fd909 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -911,9 +911,9 @@ static void flush_old_files(struct files_struct * files)
 
 char *get_task_comm(char *buf, struct task_struct *tsk)
 {
-	/* buf must be at least sizeof(tsk->comm) in size */
+	/* buf must be at least sizeof(tsk->comm) (=TASK_COMM_LEN) in size */
 	task_lock(tsk);
-	strlcpy(buf, tsk->comm, sizeof(tsk->comm));
+	strlcpy(buf, tsk->comm, TASK_COMM_LEN);
 	task_unlock(tsk);
 	return buf;
 }
@@ -921,7 +921,7 @@ char *get_task_comm(char *buf, struct task_struct *tsk)
 void set_task_comm(struct task_struct *tsk, char *buf)
 {
 	task_lock(tsk);
-	strlcpy(tsk->comm, buf, sizeof(tsk->comm));
+	strlcpy(tsk->comm, buf, TASK_COMM_LEN);
 	task_unlock(tsk);
 	perf_counter_comm(tsk);
 }
@@ -930,7 +930,7 @@ int flush_old_exec(struct linux_binprm * bprm)
 {
 	char * name;
 	int i, ch, retval;
-	char tcomm[sizeof(current->comm)];
+	char tcomm[TASK_COMM_LEN];
 
 	/*
 	 * Make sure we have a private signal table and that
-- 
1.6.3.1

Re: [PATCH 2/2] use the TASK_COMM_LEN macro instead of sizeof(tsk->comm)

[Alan Cox]

On Sun, 14 Jun 2009 18:57:48 +0200
Evgeni Golov <sargentd@die-welt.net> wrote:

> sizeof(tsk->comm) == TASK_COMM_LEN, always, so why not use it?

Because if the size ever changes the existing code will remain correct
and your changes will become a dangerous buffer overrun ?

Alan

Re: [PATCH 2/2] use the TASK_COMM_LEN macro instead of sizeof(tsk->comm)

[Evgeni Golov]

On Mon, Jun 15, 2009 at 12:14:10AM +0100, Alan Cox wrote:
> On Sun, 14 Jun 2009 18:57:48 +0200
> Evgeni Golov <sargentd@die-welt.net> wrote:
> 
> > sizeof(tsk->comm) == TASK_COMM_LEN, always, so why not use it?
> 
> Because if the size ever changes the existing code will remain correct
> and your changes will become a dangerous buffer overrun ?

But shouldn't TASK_COMM_LEN change then too?
Just wondering, in the end it's a cosmetic cange, but looking at the 
code, we rely on TASK_COMM_LEN in other places often enough to break 
something when a task->comm is not TASK_COMM_LEM big.

Regards
Evgeni