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nfsd4: fix NULL dereference in nfsd/clients display code 

We hold the cl_lock here, and that's enough to keep stateid's from going
away, but it's not enough to prevent the files they point to from going
away.  Take fi_lock and a reference and check for NULL, as we do in
other code.

Reported-by: NeilBrown <neilb@suse.de>
Fixes: 78599c42ae ("nfsd4: add file to display list of client's opens")
Reviewed-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
J. Bruce Fields 2020-07-15 13:31:36 -04:00
parent becd201492
commit 9affa43581
1 changed files with 19 additions and 1 deletions
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20
fs/nfsd/nfs4state.c
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@ -507,6 +507,17 @@ find_any_file(struct nfs4_file *f)
return ret;
}
static struct nfsd_file *find_deleg_file(struct nfs4_file *f)
{
struct nfsd_file *ret = NULL;
spin_lock(&f->fi_lock);
if (f->fi_deleg_file)
ret = nfsd_file_get(f->fi_deleg_file);
spin_unlock(&f->fi_lock);
return ret;
}
static atomic_long_t num_delegations;
unsigned long max_delegations;
@ -2444,6 +2455,8 @@ static int nfs4_show_open(struct seq_file *s, struct nfs4_stid *st)
oo = ols->st_stateowner;
nf = st->sc_file;
file = find_any_file(nf);
if (!file)
return 0;
seq_printf(s, "- ");
nfs4_show_stateid(s, &st->sc_stateid);
@ -2481,6 +2494,8 @@ static int nfs4_show_lock(struct seq_file *s, struct nfs4_stid *st)
oo = ols->st_stateowner;
nf = st->sc_file;
file = find_any_file(nf);
if (!file)
return 0;
seq_printf(s, "- ");
nfs4_show_stateid(s, &st->sc_stateid);
@ -2513,7 +2528,9 @@ static int nfs4_show_deleg(struct seq_file *s, struct nfs4_stid *st)
ds = delegstateid(st);
nf = st->sc_file;
file = nf->fi_deleg_file;
file = find_deleg_file(nf);
if (!file)
return 0;
seq_printf(s, "- ");
nfs4_show_stateid(s, &st->sc_stateid);
@ -2529,6 +2546,7 @@ static int nfs4_show_deleg(struct seq_file *s, struct nfs4_stid *st)
seq_printf(s, ", ");
nfs4_show_fname(s, file);
seq_printf(s, " }\n");
nfsd_file_put(file);
return 0;
}