[PATCH 5.15.y 0/1] smb: client: fix "df: Resource temporarily unavailable" on 5.15 stable kernel

[kovalev@altlinux.org]

ATTENTION!
Before applying this patch a conflict patch in the queue needs to be removed:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git/tree/queue-5.15/cifs-fix-off-by-one-in-smb2_query_info_init.patch

Describe bug:
After mounting a remote cifs resource, it becomes unavailable:
df: /mnt/sambashare: Resource temporarily unavailable
It was tested on the following Linux kernel:
Linux altlinux 5.15.148

The error appeared starting from kernel 5.15.147 after adding the commit [1] "smb: client: fix OOB in SMB2_query_info_init()", in which the buffer length increases by 1 as a result of changes:
.
-      iov[0].iov_len = total_len - 1 + input_len;
+      iov[0].iov_len = len;
.

[1] https://patchwork.kernel.org/project/cifs-client/patch/20231213152557.6634-2-pc@manguebit.com/

Error fixed by backported commit in next patch  adapted for the 5.15 kernel:
[PATCH 5.15.y 1/1] smb3: Replace smb2pdu 1-element arrays with flex-arrays

P.S.
I have already  backported similar changes for the 5.10.y kernel [2],
but I did not know that there was the same error on 5.15,
since I only deal with kernels 5.10 and 6.1.
Therefore, this patch is to follow the rules of backport to stable branches.

[2] https://lore.kernel.org/all/2024012613-woozy-exhume-7b9d@gregkh/T/