[PATCH rdma-next 2/8] RDMA/core: Fix use after free in ib_query_qp()

[Edward Srouji <edwards@nvidia.com>]

From: Patrisious Haddad <phaddad@nvidia.com>

When querying a QP via the netlink flow the only synchronization
mechanism for the said QP is rdma_restrack_get(), meanwhile during the
QP destroy path rdma_restrack_del() is called at the end of the
ib_destroy_qp_user() function which is too late, since by then the
vendor specific resources for said QP would already be destroyed, and
till the rdma_restrack_del() is called this QP can still be accessed,
which could cause the use after free below.

Fix this by moving the rdma_restrack_begin_del() to the start of the
ib_destroy_qp_user(), which in turn waits for all usages of the QP to be
done then removes it from the database to prevent access to it while it
is being destroyed.

RIP: 0010:ib_query_qp+0x15/0x50 [ib_core]
Code: 48 83 05 5d 8e b9 ff 01 eb b5 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 c7 46 40 00 00 00 00 48 c7 46 78 00 00 00 00 <48> 8b 07 48 8b 80 88 01 00 00 48 85 c0 74 1a 48 83 05 54 91 b9 ff
RSP: 0018:ff11000108a8f2f0 EFLAGS: 00010202
RAX: 0000000000000000 RBX: ff11000108a8f370 RCX: ff11000108a8f370
RDX: 0000000000000000 RSI: ff11000108a8f3d8 RDI: 0000000000000000
RBP: ff1100010de5a000 R08: 0000000000000e80 R09: 0000000000000004
R10: ff110001057a604c R11: 0000000000000000 R12: ff11000108a8f370
R13: ff110001090e8000 R14: 0000000000000000 R15: ff110001057a602c
FS:  00007f2ffd8db6c0(0000) GS:ff110008dc90b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000010b9a7004 CR4: 0000000000373eb0
Call Trace:
 <TASK>
 mlx5_ib_gsi_query_qp+0x21/0x50 [mlx5_ib]
 mlx5_ib_query_qp+0x689/0x9d0 [mlx5_ib]
 ib_query_qp+0x35/0x50 [ib_core]
 fill_res_qp_entry_query.isra.0+0x47/0x280 [ib_core]
 ? __wake_up+0x40/0x50
 ? netlink_broadcast_filtered+0x15a/0x550
 ? kobject_uevent_env+0x562/0x710
 ? ep_poll_callback+0x242/0x270
 ? __nla_put+0xc/0x20
 ? nla_put+0x28/0x40
 ? nla_put_string+0x2e/0x40 [ib_core]
 fill_res_qp_entry+0x138/0x190 [ib_core]
 res_get_common_dumpit+0x4a5/0x800 [ib_core]
 ? fill_res_qp_entry_query.isra.0+0x280/0x280 [ib_core]
 nldev_res_get_qp_dumpit+0x1e/0x30 [ib_core]
 netlink_dump+0x16f/0x450
 __netlink_dump_start+0x1ce/0x2e0
 rdma_nl_rcv_msg+0x1d3/0x330 [ib_core]
 ? nldev_res_get_qp_raw_dumpit+0x30/0x30 [ib_core]
 rdma_nl_rcv_skb.constprop.0.isra.0+0x108/0x180 [ib_core]
 rdma_nl_rcv+0x12/0x20 [ib_core]
 netlink_unicast+0x255/0x380
 ? __alloc_skb+0xfa/0x1e0
 netlink_sendmsg+0x1f3/0x420
 __sock_sendmsg+0x38/0x60
 ____sys_sendmsg+0x1e8/0x230
 ? copy_msghdr_from_user+0xea/0x170
 ___sys_sendmsg+0x7c/0xb0
 ? __futex_wait+0x95/0xf0
 ? __futex_wake_mark+0x40/0x40
 ? futex_wait+0x67/0x100
 ? futex_wake+0xac/0x1b0
 __sys_sendmsg+0x5f/0xb0
 do_syscall_64+0x55/0xb90
 entry_SYSCALL_64_after_hwframe+0x4b/0x53

Fixes: 514aee660df4 ("RDMA: Globally allocate and release QP memory")
Signed-off-by: Patrisious Haddad <phaddad@nvidia.com>
Reviewed-by: Michael Guralnik <michaelgur@nvidia.com>
Signed-off-by: Edward Srouji <edwards@nvidia.com>
---
 drivers/infiniband/core/verbs.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/core/verbs.c b/drivers/infiniband/core/verbs.c
index 3b613b57e269781e94e9d63ea75c7dcc46b1dacb..7abb89a4e6a019b965d36446d64609ed2c33d1c0 100644
--- a/drivers/infiniband/core/verbs.c
+++ b/drivers/infiniband/core/verbs.c
@@ -2154,6 +2154,8 @@ int ib_destroy_qp_user(struct ib_qp *qp, struct ib_udata *udata)
 	if (qp->real_qp != qp)
 		return __ib_destroy_shared_qp(qp);
 
+	rdma_restrack_begin_del(&qp->res);
+
 	sec  = qp->qp_sec;
 	if (sec)
 		ib_destroy_qp_security_begin(sec);
@@ -2166,6 +2168,7 @@ int ib_destroy_qp_user(struct ib_qp *qp, struct ib_udata *udata)
 	if (ret) {
 		if (sec)
 			ib_destroy_qp_security_abort(sec);
+		rdma_restrack_abort_del(&qp->res);
 		return ret;
 	}
 
@@ -2178,7 +2181,7 @@ int ib_destroy_qp_user(struct ib_qp *qp, struct ib_udata *udata)
 	if (sec)
 		ib_destroy_qp_security_end(sec);
 
-	rdma_restrack_del(&qp->res);
+	rdma_restrack_commit_del(&qp->res);
 	kfree(qp);
 	return ret;
 }

-- 
2.49.0