Subject: CVE-2024-46682: nfsd: prevent panic for nfsv4.0 closed files in nfs4_show_open

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

nfsd: prevent panic for nfsv4.0 closed files in nfs4_show_open

Prior to commit 3f29cc82a84c ("nfsd: split sc_status out of
sc_type") states_show() relied on sc_type field to be of valid
type before calling into a subfunction to show content of a
particular stateid. From that commit, we split the validity of
the stateid into sc_status and no longer changed sc_type to 0
while unhashing the stateid. This resulted in kernel oopsing
for nfsv4.0 opens that stay around and in nfs4_show_open()
would derefence sc_file which was NULL.

Instead, for closed open stateids forgo displaying information
that relies of having a valid sc_file.

To reproduce: mount the server with 4.0, read and close
a file and then on the server cat /proc/fs/nfsd/clients/2/states

[  513.590804] Call trace:
[  513.590925]  _raw_spin_lock+0xcc/0x160
[  513.591119]  nfs4_show_open+0x78/0x2c0 [nfsd]
[  513.591412]  states_show+0x44c/0x488 [nfsd]
[  513.591681]  seq_read_iter+0x5d8/0x760
[  513.591896]  seq_read+0x188/0x208
[  513.592075]  vfs_read+0x148/0x470
[  513.592241]  ksys_read+0xcc/0x178

The Linux kernel CVE team has assigned CVE-2024-46682 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 6.9 with commit 3f29cc82a84c and fixed in 6.10.8 with commit ba0b697de298
	Issue introduced in 6.9 with commit 3f29cc82a84c and fixed in 6.11 with commit a204501e1743

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-46682
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	fs/nfsd/nfs4state.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/ba0b697de298285301c71c258598226e06494236
	https://git.kernel.org/stable/c/a204501e1743d695ca2930ed25a2be9f8ced96d3