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net/rds: Fix MR reference counting problem

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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>
This commit is contained in:
Ka-Cheong Poon 2020-04-08 03:21:02 -07:00 committed by David S. Miller
parent e228a5d05e
commit 2fabef4f65
2 changed files with 12 additions and 21 deletions
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25
net/rds/rdma.c
View file

@ -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)

8
net/rds/rds.h
View file

@ -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);