[PATCH] knfsd : export : Fix bug of svc_export_parse()

[PATCH] knfsd : export : Fix bug of svc_export_parse()

[Wei Yongjun]

When I export /dev/null as root, and mount it from client, mount ntf4 command will frozen.

You can test it by following command:
#exportfs -i -o fsid=0,no_root_squash,insecure,rw,async *:/dev/null
#mount -t nfs4 127.0.0.1:/ /tmp

This is because in svc_export_parse() function, if check_export return 
false, after we reject the file handle, we must do cleanup the cache, 
which is not a format error of file handle.

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>

--- fs/nfsd/export.c.orig	2007-02-20 20:59:22.000000000 -0500
+++ fs/nfsd/export.c	2007-03-16 01:04:16.000000000 -0400
@@ -543,12 +543,13 @@ static int svc_export_parse(struct cache
 		if (err) goto out;
 		exp.ex_fsid = an_int;
 
-		err = check_export(nd.dentry->d_inode, exp.ex_flags);
-		if (err) goto out;
-
 		err = fsloc_parse(&mesg, buf, &exp.ex_fslocs);
 		if (err)
 			goto out;
+
+		err = check_export(nd.dentry->d_inode, exp.ex_flags);
+		if (err)
+			set_bit(CACHE_NEGATIVE, &exp.h.flags);
 	}
 
 	expp = svc_export_lookup(&exp);



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Re: [PATCH] knfsd : export : Fix bug of svc_export_parse()

[Wei Yongjun]

Nobody replied yet, but I think this is really a BUG of exportfs.
exportfs command does not check so strictly, so maybe some unreasonable
fh.key can be add to /proc/net/rpc/nfsd.fh/channel, but used this key to
find fh.handle, this always be fail and still retry.

It's this correct?

> When I export /dev/null as root, and mount it from client, mount ntf4 command will frozen.
>
> You can test it by following command:
> #exportfs -i -o fsid=0,no_root_squash,insecure,rw,async *:/dev/null
> #mount -t nfs4 127.0.0.1:/ /tmp
>
> This is because in svc_export_parse() function, if check_export return 
> false, after we reject the file handle, we must do cleanup the cache, 
> which is not a format error of file handle.
>
> Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
>
> --- fs/nfsd/export.c.orig	2007-02-20 20:59:22.000000000 -0500
> +++ fs/nfsd/export.c	2007-03-16 01:04:16.000000000 -0400
> @@ -543,12 +543,13 @@ static int svc_export_parse(struct cache
>  		if (err) goto out;
>  		exp.ex_fsid = an_int;
>  
> -		err = check_export(nd.dentry->d_inode, exp.ex_flags);
> -		if (err) goto out;
> -
>  		err = fsloc_parse(&mesg, buf, &exp.ex_fslocs);
>  		if (err)
>  			goto out;
> +
> +		err = check_export(nd.dentry->d_inode, exp.ex_flags);
> +		if (err)
> +			set_bit(CACHE_NEGATIVE, &exp.h.flags);
>  	}
>  
>  	expp = svc_export_lookup(&exp);
>   


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Re: [PATCH] knfsd : export : Fix bug of svc_export_parse()

[Neil Brown]

On Tuesday March 27, yjwei@cn.fujitsu.com wrote:
> Nobody replied yet, but I think this is really a BUG of exportfs.
> exportfs command does not check so strictly, so maybe some unreasonable
> fh.key can be add to /proc/net/rpc/nfsd.fh/channel, but used this key to
> find fh.handle, this always be fail and still retry.
> 
> It's this correct?

Sorry for not replying earlier.

Yes, you have identified a real problem, but I'm not sure I agree with
the first.

If someone (mountd) tried to tell the kernel to export "/dev/null", it
fails with an error (-ENODIR), and I think this is correct.

Mountd should respond properly to this error, which it doesn't at the
moment.
When the request comes via the MOUNT protocol from an NFSv2 or NFSv3
client, mountd will fail the mount as it should.
However when the request comes from the kernel due to an NFSv4
request, the error is just ignored.  In that case we really should be
telling the kernel that the filehandle is not valid by writing out an
appropriate message.


Maybe something like this in nfs-utils.
What do you think?

Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
 ./utils/mountd/cache.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff .prev/utils/mountd/cache.c ./utils/mountd/cache.c
--- .prev/utils/mountd/cache.c	2007-03-27 12:11:52.000000000 +1000
+++ ./utils/mountd/cache.c	2007-03-27 12:13:40.000000000 +1000
@@ -469,7 +469,8 @@ void nfsd_fh(FILE *f)
 	}
 
 	if (found)
-		cache_export_ent(dom, found, found_path);
+		if (cache_export_ent(dom, found, found_path) < 0)
+			found = 0;
 
 	qword_print(f, dom);
 	qword_printint(f, fsidtype);
@@ -619,8 +620,10 @@ void nfsd_export(FILE *f)
 	}
 
 	if (found) {
-		dump_to_cache(f, dom, path, &found->m_export);
-		mountlist_add(dom, path);
+		if (dump_to_cache(f, dom, path, &found->m_export) < 0)
+			dump_to_cache(f, dom, path, NULL);
+		else
+			mountlist_add(dom, path);
 	} else {
 		dump_to_cache(f, dom, path, NULL);
 	}

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Re: [PATCH] knfsd : export : Fix bug of svc_export_parse()

[Wei Yongjun]

  I  have test some of the export entry's type: file, dir, symlink, 
block device, char device, socket , fifo,  and dir which is a mount 
entry used your patch, this patch can resolve all of this problem.
  Thanks

Neil Brown wrote:
> On Tuesday March 27, yjwei@cn.fujitsu.com wrote:
>   
>> Nobody replied yet, but I think this is really a BUG of exportfs.
>> exportfs command does not check so strictly, so maybe some unreasonable
>> fh.key can be add to /proc/net/rpc/nfsd.fh/channel, but used this key to
>> find fh.handle, this always be fail and still retry.
>>
>> It's this correct?
>>     
>
> Sorry for not replying earlier.
>
> Yes, you have identified a real problem, but I'm not sure I agree with
> the first.
>
> If someone (mountd) tried to tell the kernel to export "/dev/null", it
> fails with an error (-ENODIR), and I think this is correct.
>
> Mountd should respond properly to this error, which it doesn't at the
> moment.
> When the request comes via the MOUNT protocol from an NFSv2 or NFSv3
> client, mountd will fail the mount as it should.
> However when the request comes from the kernel due to an NFSv4
> request, the error is just ignored.  In that case we really should be
> telling the kernel that the filehandle is not valid by writing out an
> appropriate message.
>
>
> Maybe something like this in nfs-utils.
> What do you think?
>
> Signed-off-by: Neil Brown <neilb@suse.de>
>
> ### Diffstat output
>  ./utils/mountd/cache.c |    9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff .prev/utils/mountd/cache.c ./utils/mountd/cache.c
> --- .prev/utils/mountd/cache.c	2007-03-27 12:11:52.000000000 +1000
> +++ ./utils/mountd/cache.c	2007-03-27 12:13:40.000000000 +1000
> @@ -469,7 +469,8 @@ void nfsd_fh(FILE *f)
>  	}
>  
>  	if (found)
> -		cache_export_ent(dom, found, found_path);
> +		if (cache_export_ent(dom, found, found_path) < 0)
> +			found = 0;
>  
>  	qword_print(f, dom);
>  	qword_printint(f, fsidtype);
> @@ -619,8 +620,10 @@ void nfsd_export(FILE *f)
>  	}
>  
>  	if (found) {
> -		dump_to_cache(f, dom, path, &found->m_export);
> -		mountlist_add(dom, path);
> +		if (dump_to_cache(f, dom, path, &found->m_export) < 0)
> +			dump_to_cache(f, dom, path, NULL);
> +		else
> +			mountlist_add(dom, path);
>  	} else {
>  		dump_to_cache(f, dom, path, NULL);
>  	}
>   


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