Commit b9fdf086 authored by J. Bruce Fields's avatar J. Bruce Fields Committed by Li Lingfeng
Browse files

nfsd: fix use-after-free due to delegation race 

stable inclusion
from stable-v4.19.222
commit 2becaa990b93cbd2928292c0b669d3abb6cf06d4
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I99EU2
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2becaa990b93cbd2928292c0b669d3abb6cf06d4



--------------------------------

commit 548ec080 upstream.

A delegation break could arrive as soon as we've called vfs_setlease.  A
delegation break runs a callback which immediately (in
nfsd4_cb_recall_prepare) adds the delegation to del_recall_lru.  If we
then exit nfs4_set_delegation without hashing the delegation, it will be
freed as soon as the callback is done with it, without ever being
removed from del_recall_lru.

Symptoms show up later as use-after-free or list corruption warnings,
usually in the laundromat thread.

I suspect aba2072f "nfsd: grant read delegations to clients holding
writes" made this bug easier to hit, but I looked as far back as v3.0
and it looks to me it already had the same problem.  So I'm not sure
where the bug was introduced; it may have been there from the beginning.

Cc: stable@vger.kernel.org
Signed-off-by: default avatarJ. Bruce Fields <bfields@redhat.com>
[Salvatore Bonaccorso: Backport for context changes to versions which do
not have 20b7d86f ("nfsd: use boottime for lease expiry calculation")]
Signed-off-by: default avatarSalvatore Bonaccorso <carnil@debian.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarLi Lingfeng <lilingfeng3@huawei.com>
parent 7875dd00

fs/nfsd/nfs4state.c

+7 −2
Original line number Diff line number Diff line
@@ -971,6 +971,11 @@ hash_delegation_locked(struct nfs4_delegation *dp, struct nfs4_file *fp) 
	return 0;

}



static bool delegation_hashed(struct nfs4_delegation *dp)

{

	return !(list_empty(&dp->dl_perfile));

}



static bool

unhash_delegation_locked(struct nfs4_delegation *dp)

{
@@ -978,7 +983,7 @@ unhash_delegation_locked(struct nfs4_delegation *dp) 


	lockdep_assert_held(&state_lock);



	if (list_empty(&dp->dl_perfile))

	if (!delegation_hashed(dp))

		return false;



	dp->dl_stid.sc_type = NFS4_CLOSED_DELEG_STID;
@@ -3901,7 +3906,7 @@ static void nfsd4_cb_recall_prepare(struct nfsd4_callback *cb) 
	 * queued for a lease break. Don't queue it again.

	 */

	spin_lock(&state_lock);

	if (dp->dl_time == 0) {

	if (delegation_hashed(dp) && dp->dl_time == 0) {

		dp->dl_time = get_seconds();

		list_add_tail(&dp->dl_recall_lru, &nn->del_recall_lru);

	}