runtime: Write CIFS file 'permission denied' (Linux)

I ran into this and wasn’t in a position to change all our code that writes files to CIFS shares. I investigated different kernel versions as it appeared to happen after we upgraded the OS on our hosts. It turned out to be introduced in kernel v5.5.1, in fact this commit: https://github.com/torvalds/linux/commit/d0677992d2af3d65f1c1c21de3323d09d4891537. I managed to work around it by mounting our cifs shares using the nobrl option. From https://linux.die.net/man/8/mount.cifs:

nobrl Do not send byte range lock requests to the server. This is necessary for certain applications that break with cifs style mandatory byte range locks (and most cifs servers do not yet support requesting advisory byte range locks).

After remounting shares including this option the problem went away.

I ran into this and wasn’t in a position to change all our code that writes files to CIFS shares. I investigated different kernel versions as it appeared to happen after we upgraded the OS on our hosts. It turned out to be introduced in kernel v5.5.1, in fact this commit: torvalds/linux@d067799. I managed to work around it by mounting our cifs shares using the nobrl option. From https://linux.die.net/man/8/mount.cifs:

nobrl Do not send byte range lock requests to the server. This is necessary for certain applications that break with cifs style mandatory byte range locks (and most cifs servers do not yet support requesting advisory byte range locks).

After remounting shares including this option the problem went away.

THANK YOU! THANK YOU! THANK YOU!

I have been struggling with DOTNET commands on CIFS shares for ages. This is the only thing that fixed it for me.

I also just rant into this after upgrading some linux hosts with a Azure File Share using the 3.1 runtime. Saved me a ton of additional time trying to track down the issue.

Update

thanks @wfurt, I will try as your suggestion, this result tested by single file application.

I tried use 4 ways to write file.

1. File.WriteAllText
2. new StreamWriter(path)
3. new FileStream(path, FileMode.OpenOrCreate, FileAccess.Write, FileShare.None)
4. new FileStream(path, FileMode.OpenOrCreate, FileAccess.Write, FileShare.Read)

Only 3 works fine, so FileShare should impact the result.

Sample code

class Program
{
    static int Main(string[] args)
    {
        if (args.Length == 0 || string.IsNullOrEmpty(args[0]))
        {
            Console.WriteLine("please set dir");
            return -1;
        }
        var dir = args[0];

        if (!Directory.Exists(dir))
        {
            Console.WriteLine("please set and existing dir");
            return -1;
        }
        var id = Guid.NewGuid().ToString();
        var model = 1;
        if (args.Length > 1) {
            if (!int.TryParse(args[1], out model))
                model = 1;
        }
        var path = Path.Combine(dir, id);
        
        switch (model)
        {
            case 1:
                Write1(path);break;
            case 2:
                Write2(path); break;
            case 3:
                Write3(path); break;
            case 4:
                Write4(path); break;
            default:
                return -1;
        }           
        return 0;
    }

    static void Write1(string path)
    {
        File.WriteAllText(path, "123123");
        Console.WriteLine(path);
    }

    static void Write2(string path)
    {
        using var writer = new StreamWriter(path);
        writer.Write("123123");
        Console.WriteLine(path);
    }

    static void Write3(string path)
    {
        using var fs = new FileStream(path, FileMode.OpenOrCreate, FileAccess.Write, FileShare.None);
        using var writer = new StreamWriter(fs);
        writer.Write("123123");
        Console.WriteLine(path);
    }

    static void Write4(string path)
    {
        using var fs = new FileStream(path, FileMode.OpenOrCreate, FileAccess.Write, FileShare.Read);
        using var writer = new StreamWriter(fs);
        writer.Write("123123");
        Console.WriteLine(path);
    }
}

sample log

the-host-name:/home/debugger # ./NasDebugger /mnt/debug/ 1
Unhandled exception. System.UnauthorizedAccessException: Access to the path '/mnt/debug/c5d0bccf-edc8-4b7b-8607-fab879d0da79' is denied.
 ---> System.IO.IOException: Permission denied
   --- End of inner exception stack trace ---
   at System.IO.FileStream.WriteNative(ReadOnlySpan`1 source)
   at System.IO.FileStream.FlushWriteBuffer()
   at System.IO.FileStream.FlushInternalBuffer()
   at System.IO.FileStream.Flush(Boolean flushToDisk)
   at System.IO.FileStream.Flush()
   at System.IO.StreamWriter.Flush(Boolean flushStream, Boolean flushEncoder)
   at System.IO.StreamWriter.Dispose(Boolean disposing)
   at System.IO.TextWriter.Dispose()
   at System.IO.File.WriteAllText(String path, String contents)
   at NasDebugger.Program.Write1(String path)
   at NasDebugger.Program.Main(String[] args)
Aborted (core dumped)
the-host-name:/home/debugger # ./NasDebugger /mnt/debug/ 2
/mnt/debug/5a973cdd-ce73-40ad-b483-507f3843cbce
Unhandled exception. System.UnauthorizedAccessException: Access to the path '/mnt/debug/5a973cdd-ce73-40ad-b483-507f3843cbce' is denied.
 ---> System.IO.IOException: Permission denied
   --- End of inner exception stack trace ---
   at System.IO.FileStream.WriteNative(ReadOnlySpan`1 source)
   at System.IO.FileStream.FlushWriteBuffer()
   at System.IO.FileStream.FlushInternalBuffer()
   at System.IO.FileStream.Flush(Boolean flushToDisk)
   at System.IO.FileStream.Flush()
   at System.IO.StreamWriter.Flush(Boolean flushStream, Boolean flushEncoder)
   at System.IO.StreamWriter.Dispose(Boolean disposing)
   at System.IO.TextWriter.Dispose()
   at NasDebugger.Program.Write2(String path)
   at NasDebugger.Program.Main(String[] args)
Aborted (core dumped)
the-host-name:/home/debugger # ./NasDebugger /mnt/debug/ 3
/mnt/debug/2e23f4c7-ae3d-488d-968a-a98830777305
the-host-name:/home/debugger # ./NasDebugger /mnt/debug/ 4
/mnt/debug/d82757c5-9b77-4ee0-93c5-c140a4c39f8f
Unhandled exception. System.UnauthorizedAccessException: Access to the path '/mnt/debug/d82757c5-9b77-4ee0-93c5-c140a4c39f8f' is denied.
 ---> System.IO.IOException: Permission denied
   --- End of inner exception stack trace ---
   at System.IO.FileStream.WriteNative(ReadOnlySpan`1 source)
   at System.IO.FileStream.FlushWriteBuffer()
   at System.IO.FileStream.FlushInternalBuffer()
   at System.IO.FileStream.Flush(Boolean flushToDisk)
   at System.IO.FileStream.Flush()
   at System.IO.StreamWriter.Flush(Boolean flushStream, Boolean flushEncoder)
   at System.IO.StreamWriter.Dispose(Boolean disposing)
   at System.IO.TextWriter.Dispose()
   at NasDebugger.Program.Write4(String path)
   at NasDebugger.Program.Main(String[] args)
Aborted (core dumped)