linux-kernel - [PATCH v3 2/8] dvb-frontends: ves1820: use 64-bit arithmetic instead of 32-bit

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Message-ID: <6e8742889d7c7f087e1b698409370bb5da5cd7ff.1517929336.git.gustavo@embeddedor.com>
Date:   Tue, 6 Feb 2018 10:47:09 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <garsilva@...eddedor.com>
Subject: [PATCH v3 2/8] dvb-frontends: ves1820: use 64-bit arithmetic instead
 of 32-bit

Add suffix ULL to constant 10 in order to give the compiler complete
information about the proper arithmetic to use. Notice that this
constant is used in a context that expects an expression of type
u64 (64 bits, unsigned).

The expression fpxin = state->config->xin * 10 is currently being
evaluated using 32-bit arithmetic.

Addresses-Coverity-ID: 200604 ("Unintentional integer overflow")
Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
Changes in v2:
 - Update subject and changelog to better reflect the proposed code changes.
 - Add suffix ULL to constant instead of casting a variable.

Changes in v3:
 - Mention the specific Coverity report in the commit message.

 drivers/media/dvb-frontends/ves1820.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/dvb-frontends/ves1820.c b/drivers/media/dvb-frontends/ves1820.c
index 1d89792..1760098 100644
--- a/drivers/media/dvb-frontends/ves1820.c
+++ b/drivers/media/dvb-frontends/ves1820.c
@@ -137,7 +137,7 @@ static int ves1820_set_symbolrate(struct ves1820_state *state, u32 symbolrate)
 		NDEC = 3;
 
 	/* yeuch! */
-	fpxin = state->config->xin * 10;
+	fpxin = state->config->xin * 10ULL;
 	fptmp = fpxin; do_div(fptmp, 123);
 	if (symbolrate < fptmp)
 		SFIL = 1;
-- 
2.7.4