Patch "IB/umad: Fix use of unprotected device pointer" has been added to the 4.15-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    IB/umad: Fix use of unprotected device pointer

to the 4.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ib-umad-fix-use-of-unprotected-device-pointer.patch
and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From f23a5350e43c810ca36b26d4ed4ecd9a08686f47 Mon Sep 17 00:00:00 2001
From: Jack Morgenstein <jackm@dev.mellanox.co.il>
Date: Sun, 28 Jan 2018 11:25:29 +0200
Subject: IB/umad: Fix use of unprotected device pointer

From: Jack Morgenstein <jackm@dev.mellanox.co.il>

commit f23a5350e43c810ca36b26d4ed4ecd9a08686f47 upstream.

The ib_write_umad() is protected by taking the umad file mutex.
However, it accesses file->port->ib_dev -- which is protected only by the
port's mutex (field file_mutex).

The ib_umad_remove_one() calls ib_umad_kill_port() which sets
port->ib_dev to NULL under the port mutex (NOT the file mutex).
It then sets the mad agent to "dead" under the umad file mutex.

This is a race condition -- because there is a window where
port->ib_dev is NULL, while the agent is not "dead".

As a result, we saw stack traces like:

[16490.678059] BUG: unable to handle kernel NULL pointer dereference at 00000000000000b0
[16490.678246] IP: ib_umad_write+0x29c/0xa3a [ib_umad]
[16490.678333] PGD 0 P4D 0
[16490.678404] Oops: 0000 [#1] SMP PTI
[16490.678466] Modules linked in: rdma_ucm(OE) ib_ucm(OE) rdma_cm(OE) iw_cm(OE) ib_ipoib(OE) ib_cm(OE) ib_uverbs(OE) ib_umad(OE) mlx4_en(OE) ptp pps_core mlx4_ib(OE-) ib_core(OE) mlx4_core(OE) mlx_compat
(OE) memtrack(OE) devlink mst_pciconf(OE) mst_pci(OE) netconsole nfsv3 nfs_acl nfs lockd grace fscache cfg80211 rfkill esp6_offload esp6 esp4_offload esp4 sunrpc kvm_intel kvm ppdev parport_pc irqbypass
parport joydev i2c_piix4 virtio_balloon cirrus drm_kms_helper ttm drm e1000 serio_raw virtio_pci virtio_ring virtio ata_generic pata_acpi qemu_fw_cfg [last unloaded: mlxfw]
[16490.679202] CPU: 4 PID: 3115 Comm: sminfo Tainted: G           OE   4.14.13-300.fc27.x86_64 #1
[16490.679339] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu2 04/01/2014
[16490.679477] task: ffff9cf753890000 task.stack: ffffaf70c26b0000
[16490.679571] RIP: 0010:ib_umad_write+0x29c/0xa3a [ib_umad]
[16490.679664] RSP: 0018:ffffaf70c26b3d90 EFLAGS: 00010202
[16490.679747] RAX: 0000000000000010 RBX: ffff9cf75610fd80 RCX: 0000000000000000
[16490.679856] RDX: 0000000000000001 RSI: 00007ffdf2bfd714 RDI: ffff9cf6bb2a9c00

In the above trace, ib_umad_write is trying to dereference the NULL
file->port->ib_dev pointer.

Fix this by using the agent's device pointer (the device field
in struct ib_mad_agent) -- which IS protected by the umad file mutex.

Fixes: 44c58487d51a ("IB/core: Define 'ib' and 'roce' rdma_ah_attr types")
Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/infiniband/core/user_mad.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/infiniband/core/user_mad.c
+++ b/drivers/infiniband/core/user_mad.c
@@ -500,7 +500,7 @@ static ssize_t ib_umad_write(struct file
 	}
 
 	memset(&ah_attr, 0, sizeof ah_attr);
-	ah_attr.type = rdma_ah_find_type(file->port->ib_dev,
+	ah_attr.type = rdma_ah_find_type(agent->device,
 					 file->port->port_num);
 	rdma_ah_set_dlid(&ah_attr, be16_to_cpu(packet->mad.hdr.lid));
 	rdma_ah_set_sl(&ah_attr, packet->mad.hdr.sl);


Patches currently in stable-queue which might be from jackm@dev.mellanox.co.il are

queue-4.15/ib-mlx4-fix-incorrectly-releasing-steerable-ud-qps-when-have-only-eth-ports.patch
queue-4.15/ib-umad-fix-use-of-unprotected-device-pointer.patch