[PATCH] PNP: fix unintended sign extension on left shifts

[Colin King]

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

Shifting a u8 left will cause the value to be promoted to an integer. If
the top bit of the u8 is set then the following conversion to a 64 bit
resource_size_t will sign extend the value causing the upper 32 bits
to be set in the result.

Fix this by casting the u8 value to a resource_size_t before the shift.
Original commit is pre-git history.

Signed-off-by: Colin Ian King <colin.k...@canonical.com>
---
 drivers/pnp/isapnp/core.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/drivers/pnp/isapnp/core.c b/drivers/pnp/isapnp/core.c
index 179b737280e1..c947b1673041 100644
--- a/drivers/pnp/isapnp/core.c
+++ b/drivers/pnp/isapnp/core.c
@@ -511,10 +511,14 @@ static void __init isapnp_parse_mem32_resource(struct 
pnp_dev *dev,
        unsigned char flags;
 
        isapnp_peek(tmp, size);
-       min = (tmp[4] << 24) | (tmp[3] << 16) | (tmp[2] << 8) | tmp[1];
-       max = (tmp[8] << 24) | (tmp[7] << 16) | (tmp[6] << 8) | tmp[5];
-       align = (tmp[12] << 24) | (tmp[11] << 16) | (tmp[10] << 8) | tmp[9];
-       len = (tmp[16] << 24) | (tmp[15] << 16) | (tmp[14] << 8) | tmp[13];
+       min = ((resource_size_t)tmp[4] << 24) | (tmp[3] << 16) |
+              (tmp[2] << 8) | tmp[1];
+       max = ((resource_size_t)tmp[8] << 24) | (tmp[7] << 16) |
+              (tmp[6] << 8) | tmp[5];
+       align = ((resource_size_t)tmp[12] << 24) | (tmp[11] << 16) |
+              (tmp[10] << 8) | tmp[9];
+       len = ((resource_size_t)tmp[16] << 24) | (tmp[15] << 16) |
+              (tmp[14] << 8) | tmp[13];
        flags = tmp[0];
        pnp_register_mem_resource(dev, option_flags,
                                  min, max, align, len, flags);
@@ -532,8 +536,10 @@ static void __init 
isapnp_parse_fixed_mem32_resource(struct pnp_dev *dev,
        unsigned char flags;
 
        isapnp_peek(tmp, size);
-       base = (tmp[4] << 24) | (tmp[3] << 16) | (tmp[2] << 8) | tmp[1];
-       len = (tmp[8] << 24) | (tmp[7] << 16) | (tmp[6] << 8) | tmp[5];
+       base = ((resource_size_t)tmp[4] << 24) | (tmp[3] << 16) |
+              (tmp[2] << 8) | tmp[1];
+       len = ((resource_size_t)tmp[8] << 24) | (tmp[7] << 16) |
+              (tmp[6] << 8) | tmp[5];
        flags = tmp[0];
        pnp_register_mem_resource(dev, option_flags, base, base, 0, len, flags);
 }
-- 
2.20.1