nvmem: core: Fix unintentional sign extension issue

The shifting of the u8 integer buf[3] by 24 bits to the left will
be promoted to a 32 bit signed int and then sign-extended to a
u64. In the event that the top bit of buf[3] is set then all
then all the upper 32 bits of the u64 end up as also being set
because of the sign-extension. Fix this by casting buf[i] to
a u64 before the shift.

Addresses-Coverity: ("Unintended sign extension")
Fixes: 097eb1136ebb ("nvmem: core: Add functions to make number reading easy")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index 635e3131eb5f73c686c3d08a9001a3ad0a77f87f..bca671ff4e54607ffd4e53e699b664da7d336f11 100644 (file)
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -1693,7 +1693,7 @@ int nvmem_cell_read_variable_le_u64(struct device *dev, const char *cell_id,
        /* Copy w/ implicit endian conversion */
        *val = 0;
        for (i = 0; i < len; i++)
-               *val |= buf[i] << (8 * i);
+               *val |= (uint64_t)buf[i] << (8 * i);
 
        kfree(buf);