* [PATCH] clocksource: atmel-st: Variable sr in at91rm9200_timer_interrupt() could be uninitialized
@ 2019-09-02 22:29 Yizhuo
2019-09-02 22:36 ` Alexandre Belloni
0 siblings, 1 reply; 4+ messages in thread
From: Yizhuo @ 2019-09-02 22:29 UTC (permalink / raw)
Cc: csong, zhiyunq, Yizhuo, Daniel Lezcano, Thomas Gleixner,
Nicolas Ferre, Alexandre Belloni, Ludovic Desroches,
linux-kernel, linux-arm-kernel
Inside function at91rm9200_timer_interrupt(), variable sr could
be uninitialized if regmap_read() fails. However, sr is used
to decide the control flow later in the if statement, which is
potentially unsafe. We could check the return value of
regmap_read() and print an error here.
Signed-off-by: Yizhuo <yzhai003@ucr.edu>
---
drivers/clocksource/timer-atmel-st.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/clocksource/timer-atmel-st.c b/drivers/clocksource/timer-atmel-st.c
index ab0aabfae5f0..061a3f27847e 100644
--- a/drivers/clocksource/timer-atmel-st.c
+++ b/drivers/clocksource/timer-atmel-st.c
@@ -48,8 +48,14 @@ static inline unsigned long read_CRTR(void)
static irqreturn_t at91rm9200_timer_interrupt(int irq, void *dev_id)
{
u32 sr;
+ int ret;
+
+ ret = regmap_read(regmap_st, AT91_ST_SR, &sr);
+ if (ret) {
+ pr_err("Fail to read AT91_ST_SR.\n");
+ return ret;
+ }
- regmap_read(regmap_st, AT91_ST_SR, &sr);
sr &= irqmask;
/*
--
2.17.1
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] clocksource: atmel-st: Variable sr in at91rm9200_timer_interrupt() could be uninitialized
2019-09-02 22:29 [PATCH] clocksource: atmel-st: Variable sr in at91rm9200_timer_interrupt() could be uninitialized Yizhuo
@ 2019-09-02 22:36 ` Alexandre Belloni
2019-09-03 5:56 ` Yizhuo Zhai
0 siblings, 1 reply; 4+ messages in thread
From: Alexandre Belloni @ 2019-09-02 22:36 UTC (permalink / raw)
To: Yizhuo
Cc: csong, zhiyunq, Daniel Lezcano, Thomas Gleixner, Nicolas Ferre,
Ludovic Desroches, linux-kernel, linux-arm-kernel
On 02/09/2019 15:29:46-0700, Yizhuo wrote:
> Inside function at91rm9200_timer_interrupt(), variable sr could
> be uninitialized if regmap_read() fails. However, sr is used
Could you elaborate on how this could fail?
> to decide the control flow later in the if statement, which is
> potentially unsafe. We could check the return value of
> regmap_read() and print an error here.
>
> Signed-off-by: Yizhuo <yzhai003@ucr.edu>
> ---
> drivers/clocksource/timer-atmel-st.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/clocksource/timer-atmel-st.c b/drivers/clocksource/timer-atmel-st.c
> index ab0aabfae5f0..061a3f27847e 100644
> --- a/drivers/clocksource/timer-atmel-st.c
> +++ b/drivers/clocksource/timer-atmel-st.c
> @@ -48,8 +48,14 @@ static inline unsigned long read_CRTR(void)
> static irqreturn_t at91rm9200_timer_interrupt(int irq, void *dev_id)
> {
> u32 sr;
> + int ret;
> +
> + ret = regmap_read(regmap_st, AT91_ST_SR, &sr);
> + if (ret) {
> + pr_err("Fail to read AT91_ST_SR.\n");
> + return ret;
> + }
>
> - regmap_read(regmap_st, AT91_ST_SR, &sr);
> sr &= irqmask;
>
> /*
> --
> 2.17.1
>
--
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] clocksource: atmel-st: Variable sr in at91rm9200_timer_interrupt() could be uninitialized
2019-09-02 22:36 ` Alexandre Belloni
@ 2019-09-03 5:56 ` Yizhuo Zhai
2019-09-03 8:16 ` Alexandre Belloni
0 siblings, 1 reply; 4+ messages in thread
From: Yizhuo Zhai @ 2019-09-03 5:56 UTC (permalink / raw)
To: Alexandre Belloni
Cc: Chengyu Song, Zhiyun Qian, Daniel Lezcano, Thomas Gleixner,
Nicolas Ferre, Ludovic Desroches, linux-kernel, linux-arm-kernel
In function regmap_read(), there're two places which could make the read fail.
First, if "reg" and "map->reg_stride" are not aligned, then remap_read() will
return -EINVAL without initialize variable "val".
Second, _regmap_read() could also fail and return error code if "val" is not
initialized. The caller remap_read() returns the same error code, but
at91rm9200_timer_interrupt() does not use this information.
On Mon, Sep 2, 2019 at 3:37 PM Alexandre Belloni
<alexandre.belloni@bootlin.com> wrote:
>
> On 02/09/2019 15:29:46-0700, Yizhuo wrote:
> > Inside function at91rm9200_timer_interrupt(), variable sr could
> > be uninitialized if regmap_read() fails. However, sr is used
>
> Could you elaborate on how this could fail?
>
> > to decide the control flow later in the if statement, which is
> > potentially unsafe. We could check the return value of
> > regmap_read() and print an error here.
> >
> > Signed-off-by: Yizhuo <yzhai003@ucr.edu>
> > ---
> > drivers/clocksource/timer-atmel-st.c | 8 +++++++-
> > 1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/clocksource/timer-atmel-st.c b/drivers/clocksource/timer-atmel-st.c
> > index ab0aabfae5f0..061a3f27847e 100644
> > --- a/drivers/clocksource/timer-atmel-st.c
> > +++ b/drivers/clocksource/timer-atmel-st.c
> > @@ -48,8 +48,14 @@ static inline unsigned long read_CRTR(void)
> > static irqreturn_t at91rm9200_timer_interrupt(int irq, void *dev_id)
> > {
> > u32 sr;
> > + int ret;
> > +
> > + ret = regmap_read(regmap_st, AT91_ST_SR, &sr);
> > + if (ret) {
> > + pr_err("Fail to read AT91_ST_SR.\n");
> > + return ret;
> > + }
> >
> > - regmap_read(regmap_st, AT91_ST_SR, &sr);
> > sr &= irqmask;
> >
> > /*
> > --
> > 2.17.1
> >
>
> --
> Alexandre Belloni, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com
--
Kind Regards,
Yizhuo Zhai
Computer Science, Graduate Student
University of California, Riverside
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] clocksource: atmel-st: Variable sr in at91rm9200_timer_interrupt() could be uninitialized
2019-09-03 5:56 ` Yizhuo Zhai
@ 2019-09-03 8:16 ` Alexandre Belloni
0 siblings, 0 replies; 4+ messages in thread
From: Alexandre Belloni @ 2019-09-03 8:16 UTC (permalink / raw)
To: Yizhuo Zhai
Cc: Chengyu Song, Zhiyun Qian, Daniel Lezcano, Thomas Gleixner,
Nicolas Ferre, Ludovic Desroches, linux-kernel, linux-arm-kernel
On 02/09/2019 22:56:48-0700, Yizhuo Zhai wrote:
> In function regmap_read(), there're two places which could make the read fail.
>
> First, if "reg" and "map->reg_stride" are not aligned, then remap_read() will
> return -EINVAL without initialize variable "val".
>
A quick look at of_syscon_register would show you that this is not
possible.
> Second, _regmap_read() could also fail and return error code if "val" is not
> initialized. The caller remap_read() returns the same error code, but
> at91rm9200_timer_interrupt() does not use this information.
>
How would _regmap_read fail exactly?
> On Mon, Sep 2, 2019 at 3:37 PM Alexandre Belloni
> <alexandre.belloni@bootlin.com> wrote:
> >
> > On 02/09/2019 15:29:46-0700, Yizhuo wrote:
> > > Inside function at91rm9200_timer_interrupt(), variable sr could
> > > be uninitialized if regmap_read() fails. However, sr is used
> >
> > Could you elaborate on how this could fail?
> >
> > > to decide the control flow later in the if statement, which is
> > > potentially unsafe. We could check the return value of
> > > regmap_read() and print an error here.
> > >
> > > Signed-off-by: Yizhuo <yzhai003@ucr.edu>
> > > ---
> > > drivers/clocksource/timer-atmel-st.c | 8 +++++++-
> > > 1 file changed, 7 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/clocksource/timer-atmel-st.c b/drivers/clocksource/timer-atmel-st.c
> > > index ab0aabfae5f0..061a3f27847e 100644
> > > --- a/drivers/clocksource/timer-atmel-st.c
> > > +++ b/drivers/clocksource/timer-atmel-st.c
> > > @@ -48,8 +48,14 @@ static inline unsigned long read_CRTR(void)
> > > static irqreturn_t at91rm9200_timer_interrupt(int irq, void *dev_id)
> > > {
> > > u32 sr;
> > > + int ret;
> > > +
> > > + ret = regmap_read(regmap_st, AT91_ST_SR, &sr);
> > > + if (ret) {
> > > + pr_err("Fail to read AT91_ST_SR.\n");
> > > + return ret;
> > > + }
> > >
> > > - regmap_read(regmap_st, AT91_ST_SR, &sr);
> > > sr &= irqmask;
> > >
> > > /*
> > > --
> > > 2.17.1
> > >
> >
> > --
> > Alexandre Belloni, Bootlin
> > Embedded Linux and Kernel engineering
> > https://bootlin.com
>
>
>
> --
> Kind Regards,
>
> Yizhuo Zhai
>
> Computer Science, Graduate Student
> University of California, Riverside
--
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
^ permalink raw reply [flat|nested] 4+ messages in thread
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2019-09-02 22:29 [PATCH] clocksource: atmel-st: Variable sr in at91rm9200_timer_interrupt() could be uninitialized Yizhuo
2019-09-02 22:36 ` Alexandre Belloni
2019-09-03 5:56 ` Yizhuo Zhai
2019-09-03 8:16 ` Alexandre Belloni
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