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nfsd: fix deadlock secinfo+readdir compound

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commit 2f6fc056e899bd0144a08da5cacaecbe8997cd74 upstream.

nfsd_lookup_dentry exits with the parent filehandle locked.  fh_put also
unlocks if necessary (nfsd filehandle locking is probably too lenient),
so it gets unlocked eventually, but if the following op in the compound
needs to lock it again, we can deadlock.

A fuzzer ran into this; normal clients don't send a secinfo followed by
a readdir in the same compound.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
J. Bruce Fields 2016-03-02 16:36:21 -08:00 committed by Greg Kroah-Hartman
parent 9ef1ecc409
commit 56fb92d684
1 changed files with 1 additions and 0 deletions
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fs/nfsd/nfs4proc.c
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@ -877,6 +877,7 @@ nfsd4_secinfo(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
&exp, &dentry);
if (err)
return err;
fh_unlock(&cstate->current_fh);
if (d_really_is_negative(dentry)) {
exp_put(exp);
err = nfserr_noent;