[PATCH] staging: gasket: Check the return value of gasket_get_bar_index()

[Oscar Carter]

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.car...@gmx.com>
---
 drivers/staging/gasket/gasket_core.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/staging/gasket/gasket_core.c 
b/drivers/staging/gasket/gasket_core.c
index 8e0575fcb4c8..67325fbaf760 100644
--- a/drivers/staging/gasket/gasket_core.c
+++ b/drivers/staging/gasket/gasket_core.c
@@ -925,6 +925,10 @@ do_map_region(const struct gasket_dev *gasket_dev, struct 
vm_area_struct *vma,
                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) {
                /*
--
2.20.1