4.15-stable review patch. If anyone has any objections, please let me know.
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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);