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    Subject[PATCH 4.7 044/184] NFSv4.1: Fix Oopsable condition in server callback races
    Date
    4.7-stable review patch.  If anyone has any objections, please let me know.

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

    From: Trond Myklebust <trond.myklebust@primarydata.com>

    commit e09c978aae5bedfdb379be80363b024b7d82638b upstream.

    The slot table hasn't been an array since v3.7. Ensure that we
    use nfs4_lookup_slot() to access the slot correctly.

    Fixes: 87dda67e7386 ("NFSv4.1: Allow SEQUENCE to resize the slot table...")
    Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/nfs/callback_proc.c | 5 +----
    fs/nfs/nfs4session.c | 33 +++++++++++++++++++++++++++++++++
    fs/nfs/nfs4session.h | 1 +
    3 files changed, 35 insertions(+), 4 deletions(-)

    --- a/fs/nfs/callback_proc.c
    +++ b/fs/nfs/callback_proc.c
    @@ -430,11 +430,8 @@ static bool referring_call_exists(struct
    ((u32 *)&rclist->rcl_sessionid.data)[3],
    ref->rc_sequenceid, ref->rc_slotid);

    - spin_lock(&tbl->slot_tbl_lock);
    - status = (test_bit(ref->rc_slotid, tbl->used_slots) &&
    - tbl->slots[ref->rc_slotid].seq_nr ==
    + status = nfs4_slot_seqid_in_use(tbl, ref->rc_slotid,
    ref->rc_sequenceid);
    - spin_unlock(&tbl->slot_tbl_lock);
    if (status)
    goto out;
    }
    --- a/fs/nfs/nfs4session.c
    +++ b/fs/nfs/nfs4session.c
    @@ -172,6 +172,39 @@ struct nfs4_slot *nfs4_lookup_slot(struc
    return ERR_PTR(-E2BIG);
    }

    +static int nfs4_slot_get_seqid(struct nfs4_slot_table *tbl, u32 slotid,
    + u32 *seq_nr)
    + __must_hold(&tbl->slot_tbl_lock)
    +{
    + struct nfs4_slot *slot;
    +
    + slot = nfs4_lookup_slot(tbl, slotid);
    + if (IS_ERR(slot))
    + return PTR_ERR(slot);
    + *seq_nr = slot->seq_nr;
    + return 0;
    +}
    +
    +/*
    + * nfs4_slot_seqid_in_use - test if a slot sequence id is still in use
    + *
    + * Given a slot table, slot id and sequence number, determine if the
    + * RPC call in question is still in flight. This function is mainly
    + * intended for use by the callback channel.
    + */
    +bool nfs4_slot_seqid_in_use(struct nfs4_slot_table *tbl, u32 slotid, u32 seq_nr)
    +{
    + u32 cur_seq;
    + bool ret = false;
    +
    + spin_lock(&tbl->slot_tbl_lock);
    + if (nfs4_slot_get_seqid(tbl, slotid, &cur_seq) == 0 &&
    + cur_seq == seq_nr && test_bit(slotid, tbl->used_slots))
    + ret = true;
    + spin_unlock(&tbl->slot_tbl_lock);
    + return ret;
    +}
    +
    /*
    * nfs4_alloc_slot - efficiently look for a free slot
    *
    --- a/fs/nfs/nfs4session.h
    +++ b/fs/nfs/nfs4session.h
    @@ -78,6 +78,7 @@ extern int nfs4_setup_slot_table(struct
    extern void nfs4_shutdown_slot_table(struct nfs4_slot_table *tbl);
    extern struct nfs4_slot *nfs4_alloc_slot(struct nfs4_slot_table *tbl);
    extern struct nfs4_slot *nfs4_lookup_slot(struct nfs4_slot_table *tbl, u32 slotid);
    +extern bool nfs4_slot_seqid_in_use(struct nfs4_slot_table *tbl, u32 slotid, u32 seq_nr);
    extern bool nfs4_try_to_lock_slot(struct nfs4_slot_table *tbl, struct nfs4_slot *slot);
    extern void nfs4_free_slot(struct nfs4_slot_table *tbl, struct nfs4_slot *slot);
    extern void nfs4_slot_tbl_drain_complete(struct nfs4_slot_table *tbl);

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