[PATCH 5.6 088/118] staging: gasket: Check the return value of gasket_get_bar_index()

[Greg Kroah-Hartman]

From: Oscar Carter <oscar.carter@xxxxxxx>

commit 769acc3656d93aaacada814939743361d284fd87 upstream.

Check the return value of gasket_get_bar_index function as it can return
a negative one (-EINVAL). If this happens, a negative index is used in
the "gasket_dev->bar_data" array.

Addresses-Coverity-ID: 1438542 ("Negative array index read")
Fixes: 9a69f5087ccc2 ("drivers/staging: Gasket driver framework + Apex driver")
Signed-off-by: Oscar Carter <oscar.carter@xxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx>
Reviewed-by: Richard Yeh <rcy@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200501155118.13380-1-oscar.carter@xxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/staging/gasket/gasket_core.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/staging/gasket/gasket_core.c
+++ b/drivers/staging/gasket/gasket_core.c
@@ -926,6 +926,10 @@ do_map_region(const struct gasket_dev *g
 		gasket_get_bar_index(gasket_dev,
 				     (vma->vm_pgoff << PAGE_SHIFT) +
 				     driver_desc->legacy_mmap_address_offset);
+
+	if (bar_index < 0)
+		return DO_MAP_REGION_INVALID;
+
 	phys_base = gasket_dev->bar_data[bar_index].phys_base + phys_offset;
 	while (mapped_bytes < map_length) {
 		/*