cifs mount fails since update to kernel 4.13 unless vers= is specified

asked 2017-10-23 15:28:42 -0500

smartdarena gravatar image

I am using Fedora 25. This just started after recently running a dnf update. I believe the kernel update to 4.13 has introduced this.

If I try to do a cifs mount like I always use to, for example mount -o username=me // /mnt/smb, I get the output

mount error(5): Input/output error

and in dmesg

[ 2586.985685] No dialect specified on mount. Default has changed to a more secure dialect, SMB2.1 or later (e.g. SMB3), from CIFS (SMB1). To use the less secure SMB1 dialect to access old servers which do not support SMB3 (or SMB2.1) specify vers=1.0 on mount.
[ 2587.456993] CIFS VFS: protocol revalidation - security settings mismatch
[ 2587.457757] CIFS VFS: session ffff9dd46a208800 has no tcon available for a dfs referral request
[ 2587.458414] CIFS VFS: cifs_mount failed w/return code = -5

Now, I get that there was a change in the default SMB protocol and whatnot, and I can specify vers=1.0, but the odd thing here is that my server does actually seem to support SMB 2.1 and 3.0. If I mount the share with vers=2.1 or vers=3.0 it works fine.

So, why is it failing only when I don't specify the vers=, even though my server does support SMB3 and 2.1?


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Hi, Isn't this your same issue? Bugzilla 1474539

casep gravatar imagecasep ( 2017-10-24 05:09:34 -0500 )edit

The difference is all of those people seem to have servers that just didn't support SMB 2.1 or 3.0, so they had to add vers=1.0 or vers=2.0 which worked, while vers=2.1 or vers=3.0 didn't.

My server does support up to 3.0. The mount works with vers=1.0, 2.0, 2.1 and 3.0....

smartdarena gravatar imagesmartdarena ( 2017-10-24 10:00:22 -0500 )edit

Hi, How do you know/test that V 3.0 is supported. The issue is that now the default on 4.13 was changed from 1,0 to 3.0 hence the problem in some servers. Yours looks like it's not responding OK to the default value. Cheers

casep gravatar imagecasep ( 2017-10-24 11:00:54 -0500 )edit

Is there a better way to confirm that it is actually using SMB 3.0 than looking at mount? I mounted the share with vers=3.0 and when running mount it shows: // on /mnt/smb type cifs (rw,relatime,vers=3.0,cache=strict,username=myuser,domain=,uid=0,noforceuid,gid=0,noforcegid,addr=,filemode=0755,dirmode=0755,nounix,serverino,mapposix,rsize=1048576,wsize=1048576,echo_interval=60,actimeo=1)

smartdarena gravatar imagesmartdarena ( 2017-10-24 12:20:14 -0500 )edit