diff mbox series

[2/2] tty: serial: samsung_tty: Fix a memory leak in s3c24xx_serial_getclk() when iterating clk

Message ID 93bf8f574310256fcea50e5c5a62b5c37e20bb14.1686285892.git.christophe.jaillet@wanadoo.fr
State New
Headers
Series [1/2] tty: serial: samsung_tty: Fix a memory leak in s3c24xx_serial_getclk() in case of error |

Commit Message

Christophe JAILLET June 9, 2023, 4:45 a.m. UTC 
  When the best clk is searched, we iterate over all possible clk.

If we find a better match, the previous one, if any, needs to be freed.
If a better match has already been found, we still need to free the new
one, otherwise it leaks.

Fixes: 5f5a7a5578c5 ("serial: samsung: switch to clkdev based clock lookup")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
This patch is speculative. Review with care.

I think that some clk_put() are also missing somewhere else in the driver
but won't be able to investigate further.
---
 drivers/tty/serial/samsung_tty.c | 8 ++++++++
 1 file changed, 8 insertions(+)

Comments

Krzysztof Kozlowski June 9, 2023, 11:53 a.m. UTC | #1 
On 09/06/2023 06:45, Christophe JAILLET wrote:
> When the best clk is searched, we iterate over all possible clk.
> 
> If we find a better match, the previous one, if any, needs to be freed.
> If a better match has already been found, we still need to free the new
> one, otherwise it leaks.
> 
> Fixes: 5f5a7a5578c5 ("serial: samsung: switch to clkdev based clock lookup")
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> ---
> This patch is speculative. Review with care.
> 


Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Best regards,
Krzysztof
Krzysztof Kozlowski June 9, 2023, 11:56 a.m. UTC | #2 
On 09/06/2023 10:57, Walter Harms wrote:
> 
> while we are here ....
> 
> perhaps INT_MAX from kernel.h ?
> 
> int   deviation = (1 << 30) - 1;
> 
> the part before looks a bit strange
> 
> if (ourport->info->has_divslot) {
>                         unsigned long div = rate / req_baud;
> 
>                         /* The UDIVSLOT register on the newer UARTs allows us to
>                          * get a divisor adjustment of 1/16th on the baud clock.
>                          *
>                          * We don't keep the UDIVSLOT value (the 16ths we
>                          * calculated by not multiplying the baud by 16) as it
>                          * is easy enough to recalculate.
>                          */
> 
>                         quot = div / 16;
>                         baud = rate / div;
> because
>    baud=rate/rate/req_baud = req_baud
> can this be simplyfied ? (or is the numeric required  ?)
> 
> 
> Homebrew abs()  kernel.h has a abs() can we use it here ?
> 
>             if (calc_deviation < 0)
>                         calc_deviation = -calc_deviation;
> 
> to the patch:
> 
> +                       /*
> +                        * If we find a better clk, release the previous one, if
> +                        * any.
> +                        */
> +                       if (!IS_ERR(*best_clk))
> +                               clk_put(*best_clk);
> 
> the intentions are good. *best_clk is user supplied (and should be NULL)
> filled & released in the next round but IMHO must be valid (is clk).
> so no need to check. (ntl clk_put seems to handle NULL and ERR )
>    if (!clk || WARN_ON_ONCE(IS_ERR(clk)))
>                 return;

Don't top-post.

Anyway, I don't understand what you want to say here.

Best regards,
Krzysztof
Andi Shyti June 10, 2023, 10:39 a.m. UTC | #3 
Hi Christophe,

On Fri, Jun 09, 2023 at 06:45:39AM +0200, Christophe JAILLET wrote:
> When the best clk is searched, we iterate over all possible clk.
> 
> If we find a better match, the previous one, if any, needs to be freed.
> If a better match has already been found, we still need to free the new
> one, otherwise it leaks.
> 
> Fixes: 5f5a7a5578c5 ("serial: samsung: switch to clkdev based clock lookup")
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> ---
> This patch is speculative. Review with care.
> 
> I think that some clk_put() are also missing somewhere else in the driver
> but won't be able to investigate further.
> ---
>  drivers/tty/serial/samsung_tty.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
> index dd751e7010e3..c07877dd25fa 100644
> --- a/drivers/tty/serial/samsung_tty.c
> +++ b/drivers/tty/serial/samsung_tty.c
> @@ -1488,10 +1488,18 @@ static unsigned int s3c24xx_serial_getclk(struct s3c24xx_uart_port *ourport,
>  			calc_deviation = -calc_deviation;
>  
>  		if (calc_deviation < deviation) {
> +			/*
> +			 * If we find a better clk, release the previous one, if
> +			 * any.
> +			 */
> +			if (!IS_ERR(*best_clk))

what is the case when *best_clk has an error in it?

Andi

> +				clk_put(*best_clk);
>  			*best_clk = clk;
>  			best_quot = quot;
>  			*clk_num = cnt;
>  			deviation = calc_deviation;
> +		} else {
> +			clk_put(clk);
>  		}
>  	}
>  
> -- 
> 2.34.1
>
Krzysztof Kozlowski June 10, 2023, 10:45 a.m. UTC | #4 
On 10/06/2023 12:39, Andi Shyti wrote:
> Hi Christophe,
> 
> On Fri, Jun 09, 2023 at 06:45:39AM +0200, Christophe JAILLET wrote:
>> When the best clk is searched, we iterate over all possible clk.
>>
>> If we find a better match, the previous one, if any, needs to be freed.
>> If a better match has already been found, we still need to free the new
>> one, otherwise it leaks.
>>
>> Fixes: 5f5a7a5578c5 ("serial: samsung: switch to clkdev based clock lookup")
>> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
>> ---
>> This patch is speculative. Review with care.
>>
>> I think that some clk_put() are also missing somewhere else in the driver
>> but won't be able to investigate further.
>> ---
>>  drivers/tty/serial/samsung_tty.c | 8 ++++++++
>>  1 file changed, 8 insertions(+)
>>
>> diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
>> index dd751e7010e3..c07877dd25fa 100644
>> --- a/drivers/tty/serial/samsung_tty.c
>> +++ b/drivers/tty/serial/samsung_tty.c
>> @@ -1488,10 +1488,18 @@ static unsigned int s3c24xx_serial_getclk(struct s3c24xx_uart_port *ourport,
>>  			calc_deviation = -calc_deviation;
>>  
>>  		if (calc_deviation < deviation) {
>> +			/*
>> +			 * If we find a better clk, release the previous one, if
>> +			 * any.
>> +			 */
>> +			if (!IS_ERR(*best_clk))
> 
> what is the case when *best_clk has an error in it?

The initial one? Open the place where the function is being called.

Best regards,
Krzysztof
Andi Shyti June 10, 2023, 10:57 a.m. UTC | #5 
Hi Krzysztof,

> On Sat, Jun 10, 2023 at 12:45:53PM +0200, Krzysztof Kozlowski wrote:
> On 10/06/2023 12:39, Andi Shyti wrote:
> > Hi Christophe,
> > 
> > On Fri, Jun 09, 2023 at 06:45:39AM +0200, Christophe JAILLET wrote:
> >> When the best clk is searched, we iterate over all possible clk.
> >>
> >> If we find a better match, the previous one, if any, needs to be freed.
> >> If a better match has already been found, we still need to free the new
> >> one, otherwise it leaks.
> >>
> >> Fixes: 5f5a7a5578c5 ("serial: samsung: switch to clkdev based clock lookup")
> >> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> >> ---
> >> This patch is speculative. Review with care.
> >>
> >> I think that some clk_put() are also missing somewhere else in the driver
> >> but won't be able to investigate further.
> >> ---
> >>  drivers/tty/serial/samsung_tty.c | 8 ++++++++
> >>  1 file changed, 8 insertions(+)
> >>
> >> diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
> >> index dd751e7010e3..c07877dd25fa 100644
> >> --- a/drivers/tty/serial/samsung_tty.c
> >> +++ b/drivers/tty/serial/samsung_tty.c
> >> @@ -1488,10 +1488,18 @@ static unsigned int s3c24xx_serial_getclk(struct s3c24xx_uart_port *ourport,
> >>  			calc_deviation = -calc_deviation;
> >>  
> >>  		if (calc_deviation < deviation) {
> >> +			/*
> >> +			 * If we find a better clk, release the previous one, if
> >> +			 * any.
> >> +			 */
> >> +			if (!IS_ERR(*best_clk))
> > 
> > what is the case when *best_clk has an error in it?
> 
> The initial one? Open the place where the function is being called.

Right!

Reviewed-by: Andi Shyti <andi.shyti@kernel.org> 

Andi

> 
> Best regards,
> Krzysztof
>
diff mbox series

Patch

diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
index dd751e7010e3..c07877dd25fa 100644
--- a/drivers/tty/serial/samsung_tty.c
+++ b/drivers/tty/serial/samsung_tty.c
@@ -1488,10 +1488,18 @@  static unsigned int s3c24xx_serial_getclk(struct s3c24xx_uart_port *ourport,
 			calc_deviation = -calc_deviation;
 
 		if (calc_deviation < deviation) {
+			/*
+			 * If we find a better clk, release the previous one, if
+			 * any.
+			 */
+			if (!IS_ERR(*best_clk))
+				clk_put(*best_clk);
 			*best_clk = clk;
 			best_quot = quot;
 			*clk_num = cnt;
 			deviation = calc_deviation;
+		} else {
+			clk_put(clk);
 		}
 	}