Comment 16 for bug 2049634

I had some difficulty with the test kernel, because the installation command wanted to remove the running kernel, so I got a warning about it. I think there was some kind of conflict with the normal 6.5.0-15 kernel. In the meantime, the kernel has been upgraded to 6.5.0-17, so I removed all older versions and tried again, and I think I managed to do it in the end:

$ uname -a
Linux rdiez-L2017 6.5.0-15-generic #15~22.04.1+TEST2049634v20240208b1-Ubuntu SMP PREEMPT_DYNAMIC Th x86_64 x86_64 x86_64 GNU/Linux

This is the output from "journalctl --dmesg --follow":

Feb 11 12:31:25 rdiez-L2017 kernel: FS-Cache: Loaded
Feb 11 12:31:25 rdiez-L2017 kernel: Key type cifs.spnego registered
Feb 11 12:31:25 rdiez-L2017 kernel: Key type cifs.idmap registered
Feb 11 12:31:25 rdiez-L2017 kernel: Use of the less secure dialect vers=1.0 is not recommended unless required for access to very old servers
Feb 11 12:31:25 rdiez-L2017 kernel: CIFS: VFS: Use of the less secure dialect vers=1.0 is not recommended unless required for access to very old servers
Feb 11 12:31:25 rdiez-L2017 kernel: CIFS: Attempting to mount //<redacted>

This is the output from mount -l:

//<redacted> on /home/rdiez/MountPoints/<redacted> type cifs (rw,noexec,relatime,vers=1.0,cache=strict,username=<redacted>,domain=<redacted>,uid=1000,noforceuid,gid=0,noforcegid,addr=<redacted>,file_mode=0666,dir_mode=0755,soft,nounix,serverino,mapposix,rsize=61440,wsize=16384,bsize=1048576,echo_interval=4,actimeo=1,closetimeo=1,user=<redacted>)

I didn't specify "wsize" (I never did), so it looks like it has automatically negotiated the wsize down to 16 KiB for that SMB 1.0 connection.

I then copied my test text file to and from the server, and there was no data corruption this time. So the patch is a step forwards.

I am still concerned though that the work-around the patch implements is needlessly unreliable, misleading and risks data corruption at the smallest user's mistake, despite repeated reasoning in the mailing list. I hope the kernel cifs guys find the real bug and fix it properly, so that this patch can be reverted soon.

By the way, during data transfer, I also get many errors like this:

Feb 11 12:41:01 rdiez-L2017 kernel: CIFS: VFS: SMB signature verification returned error = -13
Feb 11 12:41:11 rdiez-L2017 kernel: CIFS: VFS: SMB signature verification returned error = -13
...

I looked more carefully this time, and it happens when I read data back from the server. It looks like there is one such warning per read block, according to the negotiated rsize.

But these errors are "normal" over the years. I am guessing that the SMB 1.0 support is not very well polished.