On Wed, Jan 17, 2024 at 9:38 AM André Draszik [off-list ref] wrote:

Hi,

On Wed, 2024-01-17 at 15:21 +0000, Tudor Ambarus wrote:

quoted

On 1/16/24 18:21, Sam Protsenko wrote:

quoted

On Wed, Jan 10, 2024 at 4:23 AM Tudor Ambarus [off-list ref] wrote:

quoted

``max_count`` negative values are not used. Since ``port->fifosize``
is an unsigned int, make ``max_count`` the same.

Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
---
 drivers/tty/serial/samsung_tty.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
index 90c49197efc7..dbbe6b8e3ceb 100644
--- a/drivers/tty/serial/samsung_tty.c
+++ b/drivers/tty/serial/samsung_tty.c

@@ -760,8 +760,8 @@ static irqreturn_t s3c24xx_serial_rx_chars_dma(void *dev_id)
 static void s3c24xx_serial_rx_drain_fifo(struct s3c24xx_uart_port *ourport)
 {
        struct uart_port *port = &ourport->port;
+       unsigned int max_count = port->fifosize;

What if port->fifosize is 0? Then this code below:

    while (max_count-- > 0) {

would cause int overflow, if max_count is unsigned?

good catch, Sam!

Does it matter, though? As this is a post-decrement, the test is done first, and the
decrement after. Therefore, it'll still bail out as expected.

Good catch on my good catch :)

quoted

I'm thinking of amending this and add at the beginning of the method:

if (!max_count)
      return tty_flip_buffer_push(&port->state->port);

This will not help with overflow. It'll still have wrapped around after completing the
while() (always, no matter what start-value max_count had)

Cheers,
Andre'

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