From 2fabef4f65b46b261434a27ecdce291b63de8522 Mon Sep 17 00:00:00 2001 From: Ka-Cheong Poon Date: Wed, 8 Apr 2020 03:21:02 -0700 Subject: net/rds: Fix MR reference counting problem In rds_free_mr(), it calls rds_destroy_mr(mr) directly. But this defeats the purpose of reference counting and makes MR free handling impossible. It means that holding a reference does not guarantee that it is safe to access some fields. For example, In rds_cmsg_rdma_dest(), it increases the ref count, unlocks and then calls mr->r_trans->sync_mr(). But if rds_free_mr() (and rds_destroy_mr()) is called in between (there is no lock preventing this to happen), r_trans_private is set to NULL, causing a panic. Similar issue is in rds_rdma_unuse(). Reported-by: zerons Signed-off-by: Ka-Cheong Poon Acked-by: Santosh Shilimkar Signed-off-by: David S. Miller --- net/rds/rdma.c | 25 ++++++++++++------------- net/rds/rds.h | 8 -------- 2 files changed, 12 insertions(+), 21 deletions(-) (limited to 'net') diff --git a/net/rds/rdma.c b/net/rds/rdma.c index f828b66978e4..113e442101ce 100644 --- a/net/rds/rdma.c +++ b/net/rds/rdma.c @@ -101,9 +101,6 @@ static void rds_destroy_mr(struct rds_mr *mr) rdsdebug("RDS: destroy mr key is %x refcnt %u\n", mr->r_key, kref_read(&mr->r_kref)); - if (test_and_set_bit(RDS_MR_DEAD, &mr->r_state)) - return; - spin_lock_irqsave(&rs->rs_rdma_lock, flags); if (!RB_EMPTY_NODE(&mr->r_rb_node)) rb_erase(&mr->r_rb_node, &rs->rs_rdma_keys); @@ -142,7 +139,6 @@ void rds_rdma_drop_keys(struct rds_sock *rs) rb_erase(&mr->r_rb_node, &rs->rs_rdma_keys); RB_CLEAR_NODE(&mr->r_rb_node); spin_unlock_irqrestore(&rs->rs_rdma_lock, flags); - rds_destroy_mr(mr); kref_put(&mr->r_kref, __rds_put_mr_final); spin_lock_irqsave(&rs->rs_rdma_lock, flags); } @@ -436,12 +432,6 @@ int rds_free_mr(struct rds_sock *rs, char __user *optval, int optlen) if (!mr) return -EINVAL; - /* - * call rds_destroy_mr() ourselves so that we're sure it's done by the time - * we return. If we let rds_mr_put() do it it might not happen until - * someone else drops their ref. - */ - rds_destroy_mr(mr); kref_put(&mr->r_kref, __rds_put_mr_final); return 0; } @@ -466,6 +456,14 @@ void rds_rdma_unuse(struct rds_sock *rs, u32 r_key, int force) return; } + /* Get a reference so that the MR won't go away before calling + * sync_mr() below. + */ + kref_get(&mr->r_kref); + + /* If it is going to be freed, remove it from the tree now so + * that no other thread can find it and free it. + */ if (mr->r_use_once || force) { rb_erase(&mr->r_rb_node, &rs->rs_rdma_keys); RB_CLEAR_NODE(&mr->r_rb_node); @@ -479,12 +477,13 @@ void rds_rdma_unuse(struct rds_sock *rs, u32 r_key, int force) if (mr->r_trans->sync_mr) mr->r_trans->sync_mr(mr->r_trans_private, DMA_FROM_DEVICE); + /* Release the reference held above. */ + kref_put(&mr->r_kref, __rds_put_mr_final); + /* If the MR was marked as invalidate, this will * trigger an async flush. */ - if (zot_me) { - rds_destroy_mr(mr); + if (zot_me) kref_put(&mr->r_kref, __rds_put_mr_final); - } } void rds_rdma_free_op(struct rm_rdma_op *ro) diff --git a/net/rds/rds.h b/net/rds/rds.h index 3cda01cfaa56..8e18cd2aec51 100644 --- a/net/rds/rds.h +++ b/net/rds/rds.h @@ -299,19 +299,11 @@ struct rds_mr { unsigned int r_invalidate:1; unsigned int r_write:1; - /* This is for RDS_MR_DEAD. - * It would be nice & consistent to make this part of the above - * bit field here, but we need to use test_and_set_bit. - */ - unsigned long r_state; struct rds_sock *r_sock; /* back pointer to the socket that owns us */ struct rds_transport *r_trans; void *r_trans_private; }; -/* Flags for mr->r_state */ -#define RDS_MR_DEAD 0 - static inline rds_rdma_cookie_t rds_rdma_make_cookie(u32 r_key, u32 offset) { return r_key | (((u64) offset) << 32); -- cgit v1.2.3