Re: [PATCH 3/5] bfq: Check kstrtoul() return value

[weiping zhang]

> Sorry but I do not like this proposal because:
> * If invalid input is provided writing into a sysfs attribute should fail
>   instead of ignoring the invalid input silently.
> * simple_strtoul() is considered obsolete and must not be used in new code.
>   From include/linux/kernel.h:
>
> /* Obsolete, do not use.  Use kstrto instead */
>
> extern unsigned long simple_strtoul(const char *,char **,unsigned int);
> extern long simple_strtol(const char *,char **,unsigned int);
> extern unsigned long long simple_strtoull(const char *,char **,unsigned int);
> extern long long simple_strtoll(const char *,char **,unsigned int);
>

Hello Bart,

Agree with you, it seems more reasonable to give error message to user.

Thanks

Re: [PATCH 3/5] bfq: Check kstrtoul() return value

[Bart Van Assche]

On Sat, 2017-09-02 at 01:37 +0800, weiping zhang wrote:
> 2017-09-02 1:14 GMT+08:00 Paolo Valente :
> > Il giorno 30 ago 2017, alle ore 20:42, Bart Van Assche 
> >  ha scritto:
> > > 
> > > Make sysfs writes fail for invalid numbers instead of storing
> > > uninitialized data copied from the stack. This patch removes
> > > all uninitialized_var() occurrences from the BFQ source code.
> > > 
> > > Signed-off-by: Bart Van Assche 
> > > Cc: Paolo Valente 
> > 
> > Acked-by: Paolo Valente 
> 
> how about using simple_strtoul  which was used in cfq/mq-iosched.c
> *var = simple_strtoul(p, , 10);
> 
> if invalid string came from sysfs, this function just return 0,
> and there are validations after every calling bfq_var_store.

Hello Weiping,

Sorry but I do not like this proposal because:
* If invalid input is provided writing into a sysfs attribute should fail
  instead of ignoring the invalid input silently.
* simple_strtoul() is considered obsolete and must not be used in new code.
  From include/linux/kernel.h:

/* Obsolete, do not use.  Use kstrto instead */

extern unsigned long simple_strtoul(const char *,char **,unsigned int);
extern long simple_strtol(const char *,char **,unsigned int);
extern unsigned long long simple_strtoull(const char *,char **,unsigned int);
extern long long simple_strtoll(const char *,char **,unsigned int);

Bart.

Re: [PATCH 3/5] bfq: Check kstrtoul() return value

[weiping zhang]

2017-09-02 1:14 GMT+08:00 Paolo Valente :
>
>> Il giorno 30 ago 2017, alle ore 20:42, Bart Van Assche 
>>  ha scritto:
>>
>> Make sysfs writes fail for invalid numbers instead of storing
>> uninitialized data copied from the stack. This patch removes
>> all uninitialized_var() occurrences from the BFQ source code.
>>
>> Signed-off-by: Bart Van Assche 
>> Cc: Paolo Valente 
>
> Acked-by: Paolo Valente 
>

Hi Bart,

how about using simple_strtoul  which was used in cfq/mq-iosched.c
*var = simple_strtoul(p, , 10);

if invalid string came from sysfs, this function just return 0,
and there are validations after every calling bfq_var_store.

Thanks

Re: [PATCH 3/5] bfq: Check kstrtoul() return value

[Paolo Valente]

> Il giorno 30 ago 2017, alle ore 20:42, Bart Van Assche 
>  ha scritto:
> 
> Make sysfs writes fail for invalid numbers instead of storing
> uninitialized data copied from the stack. This patch removes
> all uninitialized_var() occurrences from the BFQ source code.
> 
> Signed-off-by: Bart Van Assche 
> Cc: Paolo Valente 

Acked-by: Paolo Valente 

> ---
> block/bfq-iosched.c | 52 +---
> 1 file changed, 37 insertions(+), 15 deletions(-)
> 
> diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
> index 8c11c2e827a5..cf92f16eb5f2 100644
> --- a/block/bfq-iosched.c
> +++ b/block/bfq-iosched.c
> @@ -4802,13 +4802,15 @@ static ssize_t bfq_var_show(unsigned int var, char 
> *page)
>   return sprintf(page, "%u\n", var);
> }
> 
> -static void bfq_var_store(unsigned long *var, const char *page)
> +static int bfq_var_store(unsigned long *var, const char *page)
> {
>   unsigned long new_val;
>   int ret = kstrtoul(page, 10, _val);
> 
> - if (ret == 0)
> - *var = new_val;
> + if (ret)
> + return ret;
> + *var = new_val;
> + return 0;
> }
> 
> #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)  \
> @@ -4849,8 +4851,12 @@ static ssize_t 
> \
> __FUNC(struct elevator_queue *e, const char *page, size_t count)  \
> { \
>   struct bfq_data *bfqd = e->elevator_data;   \
> - unsigned long uninitialized_var(__data);\
> - bfq_var_store(&__data, (page)); \
> + unsigned long __data;   \
> + int ret;\
> + \
> + ret = bfq_var_store(&__data, (page));   \
> + if (ret)\
> + return ret; \
>   if (__data < (MIN)) \
>   __data = (MIN); \
>   else if (__data > (MAX))\
> @@ -4877,8 +4883,12 @@ STORE_FUNCTION(bfq_slice_idle_store, 
> >bfq_slice_idle, 0, INT_MAX, 2);
> static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t 
> count)\
> { \
>   struct bfq_data *bfqd = e->elevator_data;   \
> - unsigned long uninitialized_var(__data);\
> - bfq_var_store(&__data, (page)); \
> + unsigned long __data;   \
> + int ret;\
> + \
> + ret = bfq_var_store(&__data, (page));   \
> + if (ret)\
> + return ret; \
>   if (__data < (MIN)) \
>   __data = (MIN); \
>   else if (__data > (MAX))\
> @@ -4894,9 +4904,12 @@ static ssize_t bfq_max_budget_store(struct 
> elevator_queue *e,
>   const char *page, size_t count)
> {
>   struct bfq_data *bfqd = e->elevator_data;
> - unsigned long uninitialized_var(__data);
> + unsigned long __data;
> + int ret;
> 
> - bfq_var_store(&__data, (page));
> + ret = bfq_var_store(&__data, (page));
> + if (ret)
> + return ret;
> 
>   if (__data == 0)
>   bfqd->bfq_max_budget = bfq_calc_max_budget(bfqd);
> @@ -4919,9 +4932,12 @@ static ssize_t bfq_timeout_sync_store(struct 
> elevator_queue *e,
> const char *page, size_t count)
> {
>   struct bfq_data *bfqd = e->elevator_data;
> - unsigned long uninitialized_var(__data);
> + unsigned long __data;
> + int ret;
> 
> - bfq_var_store(&__data, (page));
> + ret = bfq_var_store(&__data, (page));
> + if (ret)
> + return ret;
> 
>   if (__data < 1)
>   __data = 1;
> @@ -4939,9 +4955,12 @@ static ssize_t bfq_strict_guarantees_store(struct 
> elevator_queue *e,
>const char *page, size_t count)
> {
>   struct bfq_data *bfqd = e->elevator_data;
> - unsigned long uninitialized_var(__data);
> + unsigned long __data;
> + int ret;
> 
> - bfq_var_store(&__data, 

[PATCH 3/5] bfq: Check kstrtoul() return value

[Bart Van Assche]

Make sysfs writes fail for invalid numbers instead of storing
uninitialized data copied from the stack. This patch removes
all uninitialized_var() occurrences from the BFQ source code.

Signed-off-by: Bart Van Assche 
Cc: Paolo Valente 
---
 block/bfq-iosched.c | 52 +---
 1 file changed, 37 insertions(+), 15 deletions(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 8c11c2e827a5..cf92f16eb5f2 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -4802,13 +4802,15 @@ static ssize_t bfq_var_show(unsigned int var, char 
*page)
return sprintf(page, "%u\n", var);
 }
 
-static void bfq_var_store(unsigned long *var, const char *page)
+static int bfq_var_store(unsigned long *var, const char *page)
 {
unsigned long new_val;
int ret = kstrtoul(page, 10, _val);
 
-   if (ret == 0)
-   *var = new_val;
+   if (ret)
+   return ret;
+   *var = new_val;
+   return 0;
 }
 
 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)   \
@@ -4849,8 +4851,12 @@ static ssize_t   
\
 __FUNC(struct elevator_queue *e, const char *page, size_t count)   \
 {  \
struct bfq_data *bfqd = e->elevator_data;   \
-   unsigned long uninitialized_var(__data);\
-   bfq_var_store(&__data, (page)); \
+   unsigned long __data;   \
+   int ret;\
+   \
+   ret = bfq_var_store(&__data, (page));   \
+   if (ret)\
+   return ret; \
if (__data < (MIN)) \
__data = (MIN); \
else if (__data > (MAX))\
@@ -4877,8 +4883,12 @@ STORE_FUNCTION(bfq_slice_idle_store, 
>bfq_slice_idle, 0, INT_MAX, 2);
 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t 
count)\
 {  \
struct bfq_data *bfqd = e->elevator_data;   \
-   unsigned long uninitialized_var(__data);\
-   bfq_var_store(&__data, (page)); \
+   unsigned long __data;   \
+   int ret;\
+   \
+   ret = bfq_var_store(&__data, (page));   \
+   if (ret)\
+   return ret; \
if (__data < (MIN)) \
__data = (MIN); \
else if (__data > (MAX))\
@@ -4894,9 +4904,12 @@ static ssize_t bfq_max_budget_store(struct 
elevator_queue *e,
const char *page, size_t count)
 {
struct bfq_data *bfqd = e->elevator_data;
-   unsigned long uninitialized_var(__data);
+   unsigned long __data;
+   int ret;
 
-   bfq_var_store(&__data, (page));
+   ret = bfq_var_store(&__data, (page));
+   if (ret)
+   return ret;
 
if (__data == 0)
bfqd->bfq_max_budget = bfq_calc_max_budget(bfqd);
@@ -4919,9 +4932,12 @@ static ssize_t bfq_timeout_sync_store(struct 
elevator_queue *e,
  const char *page, size_t count)
 {
struct bfq_data *bfqd = e->elevator_data;
-   unsigned long uninitialized_var(__data);
+   unsigned long __data;
+   int ret;
 
-   bfq_var_store(&__data, (page));
+   ret = bfq_var_store(&__data, (page));
+   if (ret)
+   return ret;
 
if (__data < 1)
__data = 1;
@@ -4939,9 +4955,12 @@ static ssize_t bfq_strict_guarantees_store(struct 
elevator_queue *e,
 const char *page, size_t count)
 {
struct bfq_data *bfqd = e->elevator_data;
-   unsigned long uninitialized_var(__data);
+   unsigned long __data;
+   int ret;
 
-   bfq_var_store(&__data, (page));
+   ret = bfq_var_store(&__data, (page));
+   if (ret)
+   return ret;
 
if (__data > 1)
__data = 1;
@@ -4958,9 +4977,12 @@ static ssize_t bfq_low_latency_store(struct