2010-07-30 11:09:50

by Kulikov Vasiliy

Subject: [PATCH 8/9] fs: nfs: misused copy_to_user() return value

copy_to_user() returns nonzero value on error, this value may be any
value between 0 and requested count, not only requested count.

Signed-off-by: Kulikov Vasiliy <[email protected]>
---
fs/nfs/idmap.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c
index 21a84d4..a9f2cd5 100644
--- a/fs/nfs/idmap.c
+++ b/fs/nfs/idmap.c
@@ -362,7 +362,7 @@ idmap_pipe_upcall(struct file *filp, struct rpc_pipe_msg *msg,
unsigned long left;

left = copy_to_user(dst, data, mlen);
- if (left == mlen) {
+ if (left)
msg->errno = -EFAULT;
return -EFAULT;
}
--
1.7.0.4

2010-07-30 17:47:27

by Myklebust, Trond

Subject: Re: [PATCH 8/9] fs: nfs: misused copy_to_user() return value

On Fri, 2010-07-30 at 15:09 +0400, Kulikov Vasiliy wrote:
> copy_to_user() returns nonzero value on error, this value may be any
> value between 0 and requested count, not only requested count.
>
> Signed-off-by: Kulikov Vasiliy <[email protected]>
> ---
> fs/nfs/idmap.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c
> index 21a84d4..a9f2cd5 100644
> --- a/fs/nfs/idmap.c
> +++ b/fs/nfs/idmap.c
> @@ -362,7 +362,7 @@ idmap_pipe_upcall(struct file *filp, struct rpc_pipe_msg *msg,
> unsigned long left;
>
> left = copy_to_user(dst, data, mlen);
> - if (left == mlen) {
> + if (left)
> msg->errno = -EFAULT;
> return -EFAULT;
> }

...and we do handle the case where copy_to_user returns less than the
requested number of bytes: it is called a 'short read' and is quite
allowed in POSIX. The userland application can just call sys_read()
again...

Trond

2010-07-30 18:04:05

by Kulikov Vasiliy

Subject: Re: [PATCH 8/9] fs: nfs: misused copy_to_user() return value

On Fri, Jul 30, 2010 at 13:47 -0400, Trond Myklebust wrote:
> On Fri, 2010-07-30 at 15:09 +0400, Kulikov Vasiliy wrote:
> > copy_to_user() returns nonzero value on error, this value may be any
> > value between 0 and requested count, not only requested count.
> >
> > Signed-off-by: Kulikov Vasiliy <[email protected]>
> > ---
> > fs/nfs/idmap.c | 2 +-
> > 1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c
> > index 21a84d4..a9f2cd5 100644
> > --- a/fs/nfs/idmap.c
> > +++ b/fs/nfs/idmap.c
> > @@ -362,7 +362,7 @@ idmap_pipe_upcall(struct file *filp, struct rpc_pipe_msg *msg,
> > unsigned long left;
> >
> > left = copy_to_user(dst, data, mlen);
> > - if (left == mlen) {
> > + if (left)
> > msg->errno = -EFAULT;
> > return -EFAULT;
> > }
>
> ...and we do handle the case where copy_to_user returns less than the
> requested number of bytes: it is called a 'short read' and is quite
> allowed in POSIX. The userland application can just call sys_read()
> again...

Right, please ignore these 2 patches.

>
> Trond