diff mbox series

power: supply: da9150-fg: fix potential overflow

Message ID 20250130090030.53422-1-a.vatoropin@crpt.ru
State New
Headers show
Series power: supply: da9150-fg: fix potential overflow | expand

Commit Message

Ваторопин Андрей Jan. 30, 2025, 9 a.m. UTC 
From: Andrey Vatoropin <a.vatoropin@crpt.ru>

Size of variable sd_gain equals four bytes - DA9150_QIF_SD_GAIN_SIZE.
Size of variable shunt_val equals two bytes - DA9150_QIF_SHUNT_VAL_SIZE.

The expression sd_gain * shunt_val is currently being evaluated using
32-bit arithmetic. So during the multiplication an overflow may occur.

As the value of type 'u64' is used as storage for the eventual result, put
ULL variable at the first position of each expression in order to give the
compiler complete information about the proper arithmetic to use. According
to C99 the guaranteed width for a variable of type 'unsigned long long' >=
64 bits.

Remove the explicit cast to u64 as it is meaningless.

Just for the sake of consistency, perform the similar trick with another
expression concerning 'iavg'.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: a419b4fd9138 ("power: Add support for DA9150 Fuel-Gauge")
Signed-off-by: Andrey Vatoropin <a.vatoropin@crpt.ru> 
---
 drivers/power/supply/da9150-fg.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Sebastian Reichel Feb. 3, 2025, 3:08 p.m. UTC | #1 
On Thu, 30 Jan 2025 09:00:34 +0000, Ваторопин Андрей wrote:
> Size of variable sd_gain equals four bytes - DA9150_QIF_SD_GAIN_SIZE.
> Size of variable shunt_val equals two bytes - DA9150_QIF_SHUNT_VAL_SIZE.
> 
> The expression sd_gain * shunt_val is currently being evaluated using
> 32-bit arithmetic. So during the multiplication an overflow may occur.
> 
> As the value of type 'u64' is used as storage for the eventual result, put
> ULL variable at the first position of each expression in order to give the
> compiler complete information about the proper arithmetic to use. According
> to C99 the guaranteed width for a variable of type 'unsigned long long' >=
> 64 bits.
> 
> [...]

Applied, thanks!

[1/1] power: supply: da9150-fg: fix potential overflow
      commit: 3fb3cb4350befc4f901c54e0cb4a2a47b1302e08

Best regards,
diff mbox series

Patch

diff --git a/drivers/power/supply/da9150-fg.c b/drivers/power/supply/da9150-fg.c
index 652c1f213af1..63bec706167c 100644
--- a/drivers/power/supply/da9150-fg.c
+++ b/drivers/power/supply/da9150-fg.c
@@ -247,7 +247,7 @@  static int da9150_fg_current_avg(struct da9150_fg *fg,
 				      DA9150_QIF_SD_GAIN_SIZE);
 	da9150_fg_read_sync_end(fg);
 
-	div = (u64) (sd_gain * shunt_val * 65536ULL);
+	div = 65536ULL * sd_gain * shunt_val;
 	do_div(div, 1000000);
-	res = (u64) (iavg * 1000000ULL);
+	res = 1000000ULL * iavg;
 	do_div(res, div);