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Commit 3e7dfb16 authored by Trond Myklebust's avatar Trond Myklebust Committed by Anna Schumaker
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NFSv4: Fix CLOSE races with OPEN 



If the reply to a successful CLOSE call races with an OPEN to the same
file, we can end up scribbling over the stateid that represents the
new open state.
The race looks like:

  Client				Server
  ======				======

  CLOSE stateid A on file "foo"
					CLOSE stateid A, return stateid C
  OPEN file "foo"
					OPEN "foo", return stateid B
  Receive reply to OPEN
  Reset open state for "foo"
  Associate stateid B to "foo"

  Receive CLOSE for A
  Reset open state for "foo"
  Replace stateid B with C

The fix is to examine the argument of the CLOSE, and check for a match
with the current stateid "other" field. If the two do not match, then
the above race occurred, and we should just ignore the CLOSE.

Reported-by: default avatarBenjamin Coddington <bcodding@redhat.com>
Signed-off-by: default avatarTrond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: default avatarAnna Schumaker <Anna.Schumaker@Netapp.com>
parent 23ea44c2

fs/nfs/nfs4_fs.h

+7 −0
Original line number Diff line number Diff line
@@ -542,6 +542,13 @@ static inline bool nfs4_valid_open_stateid(const struct nfs4_state *state) 
	return test_bit(NFS_STATE_RECOVERY_FAILED, &state->flags) == 0;

}



static inline bool nfs4_state_match_open_stateid_other(const struct nfs4_state *state,

		const nfs4_stateid *stateid)

{

	return test_bit(NFS_OPEN_STATE, &state->flags) &&

		nfs4_stateid_match_other(&state->open_stateid, stateid);

}



#else



#define nfs4_close_state(a, b) do { } while (0)

fs/nfs/nfs4proc.c

+6 −6
Original line number Diff line number Diff line
@@ -1451,7 +1451,6 @@ static void nfs_resync_open_stateid_locked(struct nfs4_state *state) 
}



static void nfs_clear_open_stateid_locked(struct nfs4_state *state,

		nfs4_stateid *arg_stateid,

		nfs4_stateid *stateid, fmode_t fmode)

{

	clear_bit(NFS_O_RDWR_STATE, &state->flags);
@@ -1469,10 +1468,9 @@ static void nfs_clear_open_stateid_locked(struct nfs4_state *state, 
	}

	if (stateid == NULL)

		return;

	/* Handle races with OPEN */

	if (!nfs4_stateid_match_other(arg_stateid, &state->open_stateid) ||

	    (nfs4_stateid_match_other(stateid, &state->open_stateid) &&

	    !nfs4_stateid_is_newer(stateid, &state->open_stateid))) {

	/* Handle OPEN+OPEN_DOWNGRADE races */

	if (nfs4_stateid_match_other(stateid, &state->open_stateid) &&

	    !nfs4_stateid_is_newer(stateid, &state->open_stateid)) {

		nfs_resync_open_stateid_locked(state);

		return;

	}
@@ -1486,7 +1484,9 @@ static void nfs_clear_open_stateid(struct nfs4_state *state, 
	nfs4_stateid *stateid, fmode_t fmode)

{

	write_seqlock(&state->seqlock);

	nfs_clear_open_stateid_locked(state, arg_stateid, stateid, fmode);

	/* Ignore, if the CLOSE argment doesn't match the current stateid */

	if (nfs4_state_match_open_stateid_other(state, arg_stateid))

		nfs_clear_open_stateid_locked(state, stateid, fmode);

	write_sequnlock(&state->seqlock);

	if (test_bit(NFS_STATE_RECLAIM_NOGRACE, &state->flags))

		nfs4_schedule_state_manager(state->owner->so_server->nfs_client);