[Bugme-new] [Bug 8916] New: device files on NFS exported with root_squash are not readable/writable when they should be

[bugme-daemon at bugzilla.kernel.org]

http://bugzilla.kernel.org/show_bug.cgi?id=8916

           Summary: device files on NFS exported with root_squash are not
                    readable/writable when they should be
           Product: File System
           Version: 2.5
     KernelVersion: 2.6.22.3
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: high
          Priority: P1
         Component: NFS
        AssignedTo: trond.myklebust at fys.uio.no
        ReportedBy: developers at tefnet.pl


Problem Description:

When NFS tree is exported with restricting options (like root_squash), kernel
NFS client checks permissions to device files / named fifos against remote
server instead of just checking them locally (if device file is 0700 and owned
by root, it should be still writable by client root processes run by root, even
with root_squash)

Steps to reproduce:
# Create an export entry on the server:
mkdir /foo
mknod -m 0600 /foo/null c 1 3
echo '/foo       *(all_squash,async,ro)' >> /etc/exports
exportfs -ra

# mount it on the client:
mount server:/foo /foo
echo foo > /foo/null

It will result with:
-su: /foo/null: Permission denied

Expected behaviour: normal succesful write operation


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