On 18. 07. 23, 8:56, Sherry Sun wrote:
This patch addresses the following Coverity report, fix it by casting
sport->port.frame_time to type u64.
CID 32305660: Unintentional integer overflow (OVERFLOW_BEFORE_WIDEN)
Potentially overflowing expression sport->port.frame_time * 8U with type
unsigned int (32 bits, unsigned) is evaluated using 32-bit arithmetic,
and then used in a context that expects an expression of type u64 (64
bits, unsigned).
Fixes: cf9aa72d2f91 ("tty: serial: fsl_lpuart: optimize the timer based EOP logic")
Signed-off-by: Sherry Sun <sherry.sun@xxxxxxx>
---
drivers/tty/serial/fsl_lpuart.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index c1980ea52666..07b3b26732db 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -1373,7 +1373,7 @@ static inline int lpuart_start_rx_dma(struct lpuart_port *sport)
sport->last_residue = 0;
sport->dma_rx_timeout = max(nsecs_to_jiffies(
- sport->port.frame_time * DMA_RX_IDLE_CHARS), 1UL);
+ (u64)sport->port.frame_time * DMA_RX_IDLE_CHARS), 1UL);
Can you explain how that can overflow? In the worst case (1 start bit, 8
data bits, 2 stop bits, parity bit, address bit, 50 bauds), frame_time
would contain:
13*1e9/50 = 260,000,000. (260 ms)
Then the multiplication above is:
260,000,000*8 = 2,080,000,000. (2 seconds)
which is still less than 2^32-1.
thanks,
--
js
suse labs
