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nfsd: fix oops on mixed NFSv4/NFSv3 client access 

If an NFSv2/v3 client breaks an NFSv4 client's delegation, it will hit a
NULL dereference in nfsd_breaker_owns_lease().

Easily reproduceable with for example

	mount -overs=4.2 server:/export /mnt/
	sleep 1h </mnt/file &
	mount -overs=3 server:/export /mnt2/
	touch /mnt2/file

Reported-by: Robert Dinse <nanook@eskimo.com>
Fixes: 28df3d1539 ("nfsd: clients don't need to break their own delegations")
BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=208807
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
J. Bruce Fields 2020-08-05 15:10:11 -04:00 committed by Chuck Lever
parent 9123e3a74e
commit 34b09af4f5
1 changed files with 2 additions and 0 deletions
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2
fs/nfsd/nfs4state.c
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@ -4597,6 +4597,8 @@ static bool nfsd_breaker_owns_lease(struct file_lock *fl)
if (!i_am_nfsd())
return NULL;
rqst = kthread_data(current);
if (!rqst->rq_lease_breaker)
return NULL;
clp = *(rqst->rq_lease_breaker);
return dl->dl_stid.sc_client == clp;
}