[PATCH 3.14 175/228] target: Allow non-supporting backends to set pi_prot_type to 0

[Greg Kroah-Hartman]

3.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andy Grover <agrover@xxxxxxxxxx>

commit 448ba904160f9d8f69217c28a1692cee5afbff88 upstream.

Userspace tools assume if a value is read from configfs, it is valid
and will not cause an error if the same value is written back. The only
valid value for pi_prot_type for backends not supporting DIF is 0, so allow
this particular value to be set without returning an error.

Reported-by: Krzysztof Chojnowski <frirajder@xxxxxxxxx>
Signed-off-by: Andy Grover <agrover@xxxxxxxxxx>
Reviewed-by: Sagi Grimberg <sagig@xxxxxxxxxxxx>
Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/target/target_core_device.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -936,6 +936,10 @@ int se_dev_set_pi_prot_type(struct se_de
 		return 0;
 	}
 	if (!dev->transport->init_prot || !dev->transport->free_prot) {
+		/* 0 is only allowed value for non-supporting backends */
+		if (flag == 0)
+			return 0;
+
 		pr_err("DIF protection not supported by backend: %s\n",
 		       dev->transport->name);
 		return -ENOSYS;


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