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media: tda10071: fix unsigned sign extension overflow

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The shifting of buf[3] by 24 bits to the left will be promoted to
a 32 bit signed int and then sign-extended to an unsigned long. In
the unlikely event that the the top bit of buf[3] is set then all
then all the upper bits end up as also being set because of
the sign-extension and this affect the ev->post_bit_error sum.
Fix this by using the temporary u32 variable bit_error to avoid
the sign-extension promotion. This also removes the need to do the
computation twice.

Addresses-Coverity: ("Unintended sign extension")

Fixes: 267897a470 ("[media] tda10071: implement DVBv5 statistics")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
This commit is contained in:
Colin Ian King 2020-02-10 15:26:46 +01:00 committed by Mauro Carvalho Chehab
parent 889968a4f7
commit a7463e2dc6
1 changed files with 5 additions and 4 deletions
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7
drivers/media/dvb-frontends/tda10071.c
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@ -470,10 +470,11 @@ static int tda10071_read_status(struct dvb_frontend *fe, enum fe_status *status)
goto error;
if (dev->delivery_system == SYS_DVBS) {
dev->dvbv3_ber = buf[0] << 24 | buf[1] << 16 |
buf[2] << 8 | buf[3] << 0;
dev->post_bit_error += buf[0] << 24 | buf[1] << 16 |
u32 bit_error = buf[0] << 24 | buf[1] << 16 |
buf[2] << 8 | buf[3] << 0;
dev->dvbv3_ber = bit_error;
dev->post_bit_error += bit_error;
c->post_bit_error.stat[0].scale = FE_SCALE_COUNTER;
c->post_bit_error.stat[0].uvalue = dev->post_bit_error;
dev->block_error += buf[4] << 8 | buf[5] << 0;