diff mbox series

[10/18] tty: serial: samsung: make max_count unsigned int

Message ID 20240110102102.61587-11-tudor.ambarus@linaro.org (mailing list archive)
State Accepted
Commit b3296e7681d80c95432ad04263ac24ad61664b9a
Headers show
Series serial: samsung: gs101 updates and winter cleanup | expand

Commit Message

Tudor Ambarus Jan. 10, 2024, 10:20 a.m. UTC
``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(-)

Comments

Sam Protsenko Jan. 16, 2024, 6:21 p.m. UTC | #1
On Wed, Jan 10, 2024 at 4:23 AM Tudor Ambarus <tudor.ambarus@linaro.org> wrote:
>
> ``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?

>         unsigned int fifocnt = 0;
> -       int max_count = port->fifosize;
>         u32 ufcon, ufstat, uerstat;
>         u8 ch, flag;
>
> --
> 2.43.0.472.g3155946c3a-goog
>
>
Tudor Ambarus Jan. 17, 2024, 3:21 p.m. UTC | #2
On 1/16/24 18:21, Sam Protsenko wrote:
> On Wed, Jan 10, 2024 at 4:23 AM Tudor Ambarus <tudor.ambarus@linaro.org> wrote:
>>
>> ``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!

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);

Thanks!
ta
André Draszik Jan. 17, 2024, 3:38 p.m. UTC | #3
Hi,

On Wed, 2024-01-17 at 15:21 +0000, Tudor Ambarus wrote:
> 
> 
> On 1/16/24 18:21, Sam Protsenko wrote:
> > On Wed, Jan 10, 2024 at 4:23 AM Tudor Ambarus <tudor.ambarus@linaro.org> wrote:
> > > 
> > > ``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.

> 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'
Tudor Ambarus Jan. 17, 2024, 3:54 p.m. UTC | #4
On 1/17/24 15:38, André Draszik wrote:
>>>> +       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.

Indeed, it doesn't. This reminds me of stop replying to emails at the
end of the day :)

Cheers Andre'!
ta
Sam Protsenko Jan. 17, 2024, 4:26 p.m. UTC | #5
On Wed, Jan 17, 2024 at 9:38 AM André Draszik <andre.draszik@linaro.org> wrote:
>
> Hi,
>
> On Wed, 2024-01-17 at 15:21 +0000, Tudor Ambarus wrote:
> >
> >
> > On 1/16/24 18:21, Sam Protsenko wrote:
> > > On Wed, Jan 10, 2024 at 4:23 AM Tudor Ambarus <tudor.ambarus@linaro.org> wrote:
> > > >
> > > > ``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 :)

> > 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'
>
Sam Protsenko Jan. 17, 2024, 4:27 p.m. UTC | #6
On Wed, Jan 17, 2024 at 9:54 AM Tudor Ambarus <tudor.ambarus@linaro.org> wrote:
>
>
>
> On 1/17/24 15:38, André Draszik wrote:
> >>>> +       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.
>
> Indeed, it doesn't. This reminds me of stop replying to emails at the
> end of the day :)
>

And it reminds me to drink some coffee in the morning before doing any
reviews :) With above condition sorted, feel free to add:

Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org>

> Cheers Andre'!
> ta
diff mbox series

Patch

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;
 	unsigned int fifocnt = 0;
-	int max_count = port->fifosize;
 	u32 ufcon, ufstat, uerstat;
 	u8 ch, flag;