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authorKa-Cheong Poon <ka-cheong.poon@oracle.com>2020-04-08 13:21:02 +0300
committerDavid S. Miller <davem@davemloft.net>2020-04-09 20:22:00 +0300
commit2fabef4f65b46b261434a27ecdce291b63de8522 (patch)
tree5c318bbf58af67e56b085332648cac599973b3fb /net
parente228a5d05e9ee25878e9a40de96e7ceb579d4893 (diff)
downloadlinux-2fabef4f65b46b261434a27ecdce291b63de8522.tar.xz
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 <sironhide0null@gmail.com> Signed-off-by: Ka-Cheong Poon <ka-cheong.poon@oracle.com> Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/rds/rdma.c25
-rw-r--r--net/rds/rds.h8
2 files changed, 12 insertions, 21 deletions
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);