2009-06-14 17:05:55

by Evgeni Golov

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

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

Signed-off-by: Evgeni Golov <[email protected]>
---
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

2009-06-14 17:06:13

by Evgeni Golov

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

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

Signed-off-by: Evgeni Golov <[email protected]>
---
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

2009-06-14 23:12:58

by Alan

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

On Sun, 14 Jun 2009 18:57:48 +0200
Evgeni Golov <[email protected]> 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

2009-06-15 06:05:55

by Evgeni Golov

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

On Mon, Jun 15, 2009 at 12:14:10AM +0100, Alan Cox wrote:
> On Sun, 14 Jun 2009 18:57:48 +0200
> Evgeni Golov <[email protected]> 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