[PATCH v2 01/15] IB/srp: Fix remove_one crash due to resource exhaustion

[Bart Van Assche <bvanassche-HInyCGIudOg@public.gmane.org>]

From: Dotan Barak <dotanb-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>

If the add_one callback fails during driver load no resources are
allocated so there isn't a need to release any resources. Trying
to clean the resource may lead to the following kernel panic:

BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<ffffffffa0132331>] srp_remove_one+0x31/0x240 [ib_srp]
RIP: 0010:[<ffffffffa0132331>]  [<ffffffffa0132331>] srp_remove_one+0x31/0x240 [ib_srp]
Process rmmod (pid: 4562, threadinfo ffff8800dd738000, task ffff8801167e60c0)
Call Trace:
 [<ffffffffa024500e>] ib_unregister_client+0x4e/0x120 [ib_core]
 [<ffffffffa01361bd>] srp_cleanup_module+0x15/0x71 [ib_srp]
 [<ffffffff810ac6a4>] sys_delete_module+0x194/0x260
 [<ffffffff8100b0f2>] system_call_fastpath+0x16/0x1b

[bvanassche: Shortened patch description]
Signed-off-by: Dotan Barak <dotanb-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>
Reviewed-by: Eli Cohen <eli-VPRAkNaXOzVS1MOuV/RT9w@public.gmane.org>
Signed-off-by: Bart Van Assche <bvanassche-HInyCGIudOg@public.gmane.org>
Acked-by: Sebastian Riemer <sebastian.riemer-EIkl63zCoXaH+58JC4qpiA@public.gmane.org>
Acked-by: David Dillow <dillowda-1Heg1YXhbW8@public.gmane.org>
Cc: Roland Dreier <roland-BHEL68pLQRGGvPXPguhicg@public.gmane.org>
Cc: Vu Pham <vu-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
---
 drivers/infiniband/ulp/srp/ib_srp.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index 7ccf328..368d160 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -2507,6 +2507,8 @@ static void srp_remove_one(struct ib_device *device)
 	struct srp_target_port *target;
 
 	srp_dev = ib_get_client_data(device, &srp_client);
+	if (!srp_dev)
+		return;
 
 	list_for_each_entry_safe(host, tmp_host, &srp_dev->dev_list, list) {
 		device_unregister(&host->dev);
-- 
1.7.10.4

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