Re: [PATCH] NFS: suppressing showing of default mount port value in /proc fixed

[Chuck Lever]

On Dec 3, 2010, at 1:01 PM, Kinsbursky Stanislav wrote:

> 03.12.2010 20:35, Chuck Lever ÐÐÑÐÑ:
>> 
>> On Dec 3, 2010, at 12:11 PM, Stanislav Kinsbursky wrote:
>> 
>>> Default value for mount server port is set to NFS_UNSPEC_PORT (-1) and will not
>>> be changed during parsing mount options for mound data version 6. This default
>>> value will be showed for mountport in /proc/mounts always since current default
>>> check is for zero value. This small mistake leads to big problem, because
>>> during umount.nfs execution from old user-space utils (at least nfs-utils
>>> 1.0.9) this value will be used as the server port to connect to. This request
>>> will be rejected (since port is 65535) and thus nfs mount point can't be
>>> unmounted.
>> 
>> Note: this is only possible if /etc/mtab is a link to /proc/mounts.  Not all systems have this configuration.
>> 
> 
> I found it on CentOs 5.5 with RHEL6 kernel.
> Actually, the current patch has a specific flaw: if mount port is not passed by nfs utils using mount options version 6, then it will be set to 0 and showed in /proc/mounts as "mountport=0".

Right: zero and negative one are both special internal port values that should not be displayed in /proc/mounts.  Why not check if mountport > 0 instead?

> Another fix solution is to call "nfs_set_port(sap, &args->nfs_server.port, 0);" when parsing mount options version 6 (like in done in default casein nfs_validate_mount_data) instead of changing nfs_show_mountd_options().

I'm not sure I follow here.  Why would setting nfsport be the right thing to do?  The default case is for text-based mounts only.

> Kernel version affected: 2.6.37-rc4
>>> 
>>> Signed-off-by: Stanislav Kinsbursky<skinsbursky@xxxxxxxxxxxxx>
>>> 
>>> ---
>>> fs/nfs/super.c |    3 ++-
>>> 1 files changed, 2 insertions(+), 1 deletions(-)
>>> 
>>> diff --git a/fs/nfs/super.c b/fs/nfs/super.c
>>> index 6d6e21d..fd4cac8 100644
>>> --- a/fs/nfs/super.c
>>> +++ b/fs/nfs/super.c
>>> @@ -681,7 +681,8 @@ static void nfs_show_mountd_options(struct seq_file *m, struct nfs_server *nfss,
>>> 
>>> 	if (nfss->mountd_version || showdefaults)
>>> 		seq_printf(m, ",mountvers=%u", nfss->mountd_version);
>>> -	if (nfss->mountd_port || showdefaults)
>>> +	if (nfss->mountd_port != (unsigned short)NFS_UNSPEC_PORT ||
>>> +			showdefaults)
>>> 		seq_printf(m, ",mountport=%u", nfss->mountd_port);
>>> 
>>> 	nfs_show_mountd_netid(m, nfss, showdefaults);
>>> 
>>> --
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>> 
> 
> 
> -- 
> Best regards,
> Stanislav Kinsbursky

-- 
Chuck Lever
chuck[dot]lever[at]oracle[dot]com




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