[PATCH] memory: gpmc: fix out of bounds read and dereference on gpmc_cs[]

[Colin King]

From: Colin Ian King <colin.k...@canonical.com>

Currently the array gpmc_cs is indexed by cs before it cs is range checked
and the pointer read from this out-of-index read is dereferenced. Fix this
by performing the range check on cs before the read and the following
pointer dereference.

Addresses-Coverity: ("Negative array index read")
Fixes: 186401937927 ("memory: gpmc: Move omap gpmc code to live under drivers")
Signed-off-by: Colin Ian King <colin.k...@canonical.com>
---
 drivers/memory/omap-gpmc.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/memory/omap-gpmc.c b/drivers/memory/omap-gpmc.c
index cfa730cfd145..f80c2ea39ca4 100644
--- a/drivers/memory/omap-gpmc.c
+++ b/drivers/memory/omap-gpmc.c
@@ -1009,8 +1009,8 @@ EXPORT_SYMBOL(gpmc_cs_request);
 
 void gpmc_cs_free(int cs)
 {
-       struct gpmc_cs_data *gpmc = &gpmc_cs[cs];
-       struct resource *res = &gpmc->mem;
+       struct gpmc_cs_data *gpmc;
+       struct resource *res;
 
        spin_lock(&gpmc_mem_lock);
        if (cs >= gpmc_cs_num || cs < 0 || !gpmc_cs_reserved(cs)) {
@@ -1018,6 +1018,9 @@ void gpmc_cs_free(int cs)
                spin_unlock(&gpmc_mem_lock);
                return;
        }
+       gpmc = &gpmc_cs[cs];
+       res = &gpmc->mem;
+
        gpmc_cs_disable_mem(cs);
        if (res->flags)
                release_resource(res);
-- 
2.30.0