2005-09-22 16:20:10

by Marcelo Tosatti

Subject: [PATCH] nfs client: handle long symlinks properly

commit 87e03738fc15dc3ea4acde3a5dcb5f84b6b6152b
tree be323c0a65d7e380ad04cad1c3a80015a82056dd
parent bb52ef60b5caa8f973523eda15d3c3941f298e63
author Assar <[email protected]> Wed, 14 Sep 2005 16:59:25 -0400
committer Marcelo Tosatti <[email protected]> Thu, 22 Sep 2005 13:11:18 -0300

[PATCH] nfs client: handle long symlinks properly

In 2.4.31, the v2/3 nfs readlink accepts too long symlinks.
I have tested this by having a server return long symlinks.

diff --git a/fs/nfs/nfs2xdr.c b/fs/nfs/nfs2xdr.c
--- a/fs/nfs/nfs2xdr.c
+++ b/fs/nfs/nfs2xdr.c
@@ -571,8 +571,11 @@ nfs_xdr_readlinkres(struct rpc_rqst *req
strlen = (u32*)kmap(rcvbuf->pages[0]);
/* Convert length of symlink */
len = ntohl(*strlen);
- if (len > rcvbuf->page_len)
- len = rcvbuf->page_len;
+ if (len >= rcvbuf->page_len - sizeof(u32) || len > NFS2_MAXPATHLEN) {
+ printk(KERN_WARNING "NFS: server returned giant symlink!\n");
+ kunmap(rcvbuf->pages[0]);
+ return -ENAMETOOLONG;
+ }
*strlen = len;
/* NULL terminate the string we got */
string = (char *)(strlen + 1);
diff --git a/fs/nfs/nfs3xdr.c b/fs/nfs/nfs3xdr.c
--- a/fs/nfs/nfs3xdr.c
+++ b/fs/nfs/nfs3xdr.c
@@ -759,8 +759,11 @@ nfs3_xdr_readlinkres(struct rpc_rqst *re
strlen = (u32*)kmap(rcvbuf->pages[0]);
/* Convert length of symlink */
len = ntohl(*strlen);
- if (len > rcvbuf->page_len)
- len = rcvbuf->page_len;
+ if (len >= rcvbuf->page_len - sizeof(u32)) {
+ printk(KERN_WARNING "NFS: server returned giant symlink!\n");
+ kunmap(rcvbuf->pages[0]);
+ return -ENAMETOOLONG;
+ }
*strlen = len;
/* NULL terminate the string we got */
string = (char *)(strlen + 1);

2005-09-22 16:33:50

by Trond Myklebust

Subject: Re: [PATCH] nfs client: handle long symlinks properly

to den 22.09.2005 Klokka 13:14 (-0300) skreiv Marcelo Tosatti:
> commit 87e03738fc15dc3ea4acde3a5dcb5f84b6b6152b
> tree be323c0a65d7e380ad04cad1c3a80015a82056dd
> parent bb52ef60b5caa8f973523eda15d3c3941f298e63
> author Assar <[email protected]> Wed, 14 Sep 2005 16:59:25 -0400
> committer Marcelo Tosatti <[email protected]> Thu, 22 Sep 2005 13:11:18 -0300
>
> [PATCH] nfs client: handle long symlinks properly
>
> In 2.4.31, the v2/3 nfs readlink accepts too long symlinks.
> I have tested this by having a server return long symlinks.
>
> diff --git a/fs/nfs/nfs2xdr.c b/fs/nfs/nfs2xdr.c
> --- a/fs/nfs/nfs2xdr.c
> +++ b/fs/nfs/nfs2xdr.c
> @@ -571,8 +571,11 @@ nfs_xdr_readlinkres(struct rpc_rqst *req
> strlen = (u32*)kmap(rcvbuf->pages[0]);
> /* Convert length of symlink */
> len = ntohl(*strlen);
> - if (len > rcvbuf->page_len)
> - len = rcvbuf->page_len;
> + if (len >= rcvbuf->page_len - sizeof(u32) || len > NFS2_MAXPATHLEN) {

Shouldn't that be

if (len > rcvbuf->page_len - sizeof(u32) || len > NFS2_MAXPATHLEN)

? As long as we use page_len == PAGE_SIZE, we probably don't care, but
if someone some day decides to set a different value for page_len, then
we want to make sure that we don't end up overflowing the buffer when we
NUL-terminate.

> + printk(KERN_WARNING "NFS: server returned giant symlink!\n");

Please make this a dprintk().

> + kunmap(rcvbuf->pages[0]);
> + return -ENAMETOOLONG;
> + }
> *strlen = len;
> /* NULL terminate the string we got */
> string = (char *)(strlen + 1);
> diff --git a/fs/nfs/nfs3xdr.c b/fs/nfs/nfs3xdr.c
> --- a/fs/nfs/nfs3xdr.c
> +++ b/fs/nfs/nfs3xdr.c
> @@ -759,8 +759,11 @@ nfs3_xdr_readlinkres(struct rpc_rqst *re
> strlen = (u32*)kmap(rcvbuf->pages[0]);
> /* Convert length of symlink */
> len = ntohl(*strlen);
> - if (len > rcvbuf->page_len)
> - len = rcvbuf->page_len;
> + if (len >= rcvbuf->page_len - sizeof(u32)) {

Ditto.

> + printk(KERN_WARNING "NFS: server returned giant symlink!\n");

...and ditto.

> + kunmap(rcvbuf->pages[0]);
> + return -ENAMETOOLONG;
> + }
> *strlen = len;
> /* NULL terminate the string we got */
> string = (char *)(strlen + 1);

Cheers,
Trond

2005-09-22 16:38:51

by Assar

Subject: Re: [PATCH] nfs client: handle long symlinks properly

Trond Myklebust <[email protected]> writes:
> > diff --git a/fs/nfs/nfs2xdr.c b/fs/nfs/nfs2xdr.c
> > --- a/fs/nfs/nfs2xdr.c
> > +++ b/fs/nfs/nfs2xdr.c
> > @@ -571,8 +571,11 @@ nfs_xdr_readlinkres(struct rpc_rqst *req
> > strlen = (u32*)kmap(rcvbuf->pages[0]);
> > /* Convert length of symlink */
> > len = ntohl(*strlen);
> > - if (len > rcvbuf->page_len)
> > - len = rcvbuf->page_len;
> > + if (len >= rcvbuf->page_len - sizeof(u32) || len > NFS2_MAXPATHLEN) {
>
> Shouldn't that be
>
> if (len > rcvbuf->page_len - sizeof(u32) || len > NFS2_MAXPATHLEN)
>
> ? As long as we use page_len == PAGE_SIZE, we probably don't care, but
> if someone some day decides to set a different value for page_len, then
> we want to make sure that we don't end up overflowing the buffer when we
> NUL-terminate.

Wouldn't len == rcvbuf->page_len - sizeof(u32) mean that there isn't
room for writing the terminating NUL?

2005-09-22 16:55:43

by Trond Myklebust

Subject: Re: [PATCH] nfs client: handle long symlinks properly

to den 22.09.2005 Klokka 12:38 (-0400) skreiv Assar:
> Wouldn't len == rcvbuf->page_len - sizeof(u32) mean that there isn't
> room for writing the terminating NUL?

Yep. My bad... I was screwing up the test in my mind.

Cheers,
Trond