[PATCH] block: Fix validation of ioprio level

[Ajay Kaher]

The commit eca2040972b4 introduced a backward compatibility issue in
the function ioprio_check_cap.

Before the change, if ioprio contains a level greater than 0x7, it was
treated as -EINVAL:

    data = ioprio & 0x1FFF
    if data >= 0x7, return -EINVAL 

Since the change, if ioprio contains a level greater than 0x7 say 0x8
it is calculated as 0x0:

    level = ioprio & 0x7

To maintain backward compatibility the kernel should return -EINVAL in
the above case as well.

Fixes: eca2040972b4 ("scsi: block: ioprio: Clean up interface definition")
Signed-off-by: Ajay Kaher <ajay.kaher@xxxxxxxxxxxx>
---
 block/ioprio.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/block/ioprio.c b/block/ioprio.c
index 73301a2..f08e76b 100644
--- a/block/ioprio.c
+++ b/block/ioprio.c
@@ -30,6 +30,15 @@
 #include <linux/security.h>
 #include <linux/pid_namespace.h>
 
+static inline int ioprio_check_level(int ioprio, int max_level)
+{
+	int data = IOPRIO_PRIO_DATA(ioprio);
+
+	if (IOPRIO_BAD_VALUE(data, max_level))
+		return -EINVAL;
+	return 0;
+}
+
 int ioprio_check_cap(int ioprio)
 {
 	int class = IOPRIO_PRIO_CLASS(ioprio);
@@ -49,7 +58,7 @@ int ioprio_check_cap(int ioprio)
 			fallthrough;
 			/* rt has prio field too */
 		case IOPRIO_CLASS_BE:
-			if (level >= IOPRIO_NR_LEVELS)
+			if (ioprio_check_level(ioprio, IOPRIO_NR_LEVELS))
 				return -EINVAL;
 			break;
 		case IOPRIO_CLASS_IDLE:
-- 
2.45.1