lkml.org 
[lkml]   [2010]   [Oct]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
SubjectRe: [PATCH 2/2] net/9p: Return error on read with NULL buffer
Date
On Sat, 23 Oct 2010 12:59:57 -0700, Brad Boyer <flar@allandria.com> wrote:
> On Mon, Oct 18, 2010 at 08:10:53PM +0530, Aneesh Kumar K.V wrote:
> > This patch ensures that a read(fd, NULL, 0 ) returns EFAULT on a 9p file.
>
> Is there some specific reason you want this behavior? I believe the
> generic Linux code returns success in this case. I tried this exact
> system call with fd being a pty or a file on ext3 and got 0 for both.

Linux code return 0 in case count == 0;
This is what i find on ext4.

open("a.c", O_RDONLY) = 3
read(3, 0, 10) = -1 EFAULT (Bad address)

open("a.c", O_RDONLY) = 3
read(3, NULL, 0) = 0

This patch ensure that we get the behaviour as in case one in case of 9p
file system. But patch broke the behaviour in step 2. So below is the
updated one

commit bd1717e5300ab0bb9aa2df139ffbc5e49f1baeb6
Author: Sanchit Garg <sancgarg@linux.vnet.ibm.com>
Date: Tue Oct 19 09:17:02 2010 +0530

net/9p: Return error on read with NULL buffer

This patch ensures that a read(fd, NULL, 10) returns EFAULT on a 9p file.

Signed-off-by: Sanchit Garg <sancgarg@linux.vnet.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

diff --git a/net/9p/client.c b/net/9p/client.c
index e141e46..dbca5b3 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -1333,16 +1333,13 @@ p9_client_read(struct p9_fid *fid, char *data, char __user *udata, u64 offset,

if (data) {
memmove(data, dataptr, count);
- }
-
- if (udata) {
+ } else {
err = copy_to_user(udata, dataptr, count);
if (err) {
err = -EFAULT;
goto free_and_error;
}
}
-
p9_free_req(clnt, req);
return count;


-aneesh


\
 
 \ /
  Last update: 2010-10-24 16:35    [W:0.033 / U:1.192 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site