[PATCH 4.14 129/167] xprtrdma: Fix BUG after a device removal

Greg Kroah-Hartman
2018-02-21T13:03:41Z

From: Chuck Lever <chuck.lever@oracle.com>

commit e89e8d8fcdc6751e86ccad794b052fe67e6ad619 upstream.

Michal Kalderon reports a BUG that occurs just after device removal:

[ 169.112490] rpcrdma: removing device qedr0 for 192.168.110.146:20049
[ 169.143909] BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
[ 169.181837] IP: rpcrdma_dma_unmap_regbuf+0xa/0x60 [rpcrdma]

The RPC/RDMA client transport attempts to allocate some resources
on demand. Registered buffers are one such resource. These are
allocated (or re-allocated) by xprt_rdma_allocate to hold RPC Call
and Reply messages. A hardware resource is associated with each of
these buffers, as they can be used for a Send or Receive Work
Request.

If a device is removed from under an NFS/RDMA mount, the transport
layer is responsible for releasing all hardware resources before
the device can be finally unplugged. A BUG results when the NFS
mount hasn't yet seen much activity: the transport tries to release
resources that haven't yet been allocated.

rpcrdma_free_regbuf() already checks for this case, so just move
that check to cover the DEVICE_REMOVAL case as well.

Reported-by: Michal Kalderon <Michal.Kalderon@cavium.com>
Fixes: bebd031866ca ("xprtrdma: Support unplugging an HCA ...")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Tested-by: Michal Kalderon <Michal.Kalderon@cavium.com>
Cc: stable@vger.kernel.org # v4.12+
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/sunrpc/xprtrdma/verbs.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -1331,6 +1331,9 @@ __rpcrdma_dma_map_regbuf(struct rpcrdma_
static void
rpcrdma_dma_unmap_regbuf(struct rpcrdma_regbuf *rb)
{
+ if (!rb)
+ return;
+
if (!rpcrdma_regbuf_is_mapped(rb))
return;

@@ -1346,9 +1349,6 @@ rpcrdma_dma_unmap_regbuf(struct rpcrdma_
void
rpcrdma_free_regbuf(struct rpcrdma_regbuf *rb)
{
- if (!rb)
- return;
-
rpcrdma_dma_unmap_regbuf(rb);
kfree(rb);
}