[patch] tracing: Remove an unneeded check

[patch] tracing: Remove an unneeded check

[Dan Carpenter]

memcpy() returns a pointer to "bug".  Hopefully, it's not NULL here or
we would already have Oopsed.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ed7b5d1..c2d5b71 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -629,7 +629,6 @@ ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf, size_t cnt)
 static ssize_t trace_seq_to_buffer(struct trace_seq *s, void *buf, size_t cnt)
 {
 	int len;
-	void *ret;
 
 	if (s->len <= s->readpos)
 		return -EBUSY;
@@ -637,9 +636,7 @@ static ssize_t trace_seq_to_buffer(struct trace_seq *s, void *buf, size_t cnt)
 	len = s->len - s->readpos;
 	if (cnt > len)
 		cnt = len;
-	ret = memcpy(buf, s->buffer + s->readpos, cnt);
-	if (!ret)
-		return -EFAULT;
+	memcpy(buf, s->buffer + s->readpos, cnt);
 
 	s->readpos += cnt;
 	return cnt;

Re: [patch] tracing: Remove an unneeded check

[Steven Rostedt]

On Fri, 2012-04-20 at 09:31 +0300, Dan Carpenter wrote:
> memcpy() returns a pointer to "bug".  Hopefully, it's not NULL here or
> we would already have Oopsed.

You're right that the ret is useless, and the real bug was already fixed
(the possibility that buf could be an invalid pointer).

Not only is this needed, but also get rid of the ret < 0 check in
tracing_splice_read_pipe().

-- Steve

Re: [patch] tracing: Remove an unneeded check

[Dan Carpenter]

On Fri, Apr 20, 2012 at 09:51:21AM -0400, Steven Rostedt wrote:
> On Fri, 2012-04-20 at 09:31 +0300, Dan Carpenter wrote:
> > memcpy() returns a pointer to "bug".  Hopefully, it's not NULL here or
> > we would already have Oopsed.
> 
> You're right that the ret is useless, and the real bug was already fixed
> (the possibility that buf could be an invalid pointer).
> 
> Not only is this needed, but also get rid of the ret < 0 check in
> tracing_splice_read_pipe().
> 

We still return -EBUSY so we need the check.

regards,
dan carpenter

Re: [patch] tracing: Remove an unneeded check

[Steven Rostedt]

On Fri, 2012-04-20 at 17:03 +0300, Dan Carpenter wrote:
> On Fri, Apr 20, 2012 at 09:51:21AM -0400, Steven Rostedt wrote:
> > On Fri, 2012-04-20 at 09:31 +0300, Dan Carpenter wrote:
> > > memcpy() returns a pointer to "bug".  Hopefully, it's not NULL here or
> > > we would already have Oopsed.
> > 
> > You're right that the ret is useless, and the real bug was already fixed
> > (the possibility that buf could be an invalid pointer).
> > 
> > Not only is this needed, but also get rid of the ret < 0 check in
> > tracing_splice_read_pipe().
> > 
> 
> We still return -EBUSY so we need the check.

Hmm, you're right. I need to take a deeper look at this code. It looks
like it can be cleaned up a bit more (the splice code).

OK, your patch is good as is. I'll add it in my 3.5 queue, and add a
mental note to look at this code again.

Thanks,

-- Steve

[tip:perf/core] tracing: Remove an unneeded check in trace_seq_buffer()

[tip-bot for Dan Carpenter]

Commit-ID:  5a26c8f0cf1e95106858bb4e23ca6dd14c9b842f
Gitweb:     http://git.kernel.org/tip/5a26c8f0cf1e95106858bb4e23ca6dd14c9b842f
Author:     Dan Carpenter <dan.carpenter@oracle.com>
AuthorDate: Fri, 20 Apr 2012 09:31:45 +0300
Committer:  Steven Rostedt <rostedt@goodmis.org>
CommitDate: Mon, 23 Apr 2012 21:16:10 -0400

tracing: Remove an unneeded check in trace_seq_buffer()

memcpy() returns a pointer to "bug".  Hopefully, it's not NULL here or
we would already have Oopsed.

Link: http://lkml.kernel.org/r/20120420063145.GA22649@elgon.mountain

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/trace.c |    5 +----
 1 files changed, 1 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 1ab8e35..bbcde54 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -629,7 +629,6 @@ ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf, size_t cnt)
 static ssize_t trace_seq_to_buffer(struct trace_seq *s, void *buf, size_t cnt)
 {
 	int len;
-	void *ret;
 
 	if (s->len <= s->readpos)
 		return -EBUSY;
@@ -637,9 +636,7 @@ static ssize_t trace_seq_to_buffer(struct trace_seq *s, void *buf, size_t cnt)
 	len = s->len - s->readpos;
 	if (cnt > len)
 		cnt = len;
-	ret = memcpy(buf, s->buffer + s->readpos, cnt);
-	if (!ret)
-		return -EFAULT;
+	memcpy(buf, s->buffer + s->readpos, cnt);
 
 	s->readpos += cnt;
 	return cnt;