[PATCH] kernel: kallsyms: parameters checking, for EXPORT_SYMBOL_GPL functions

[PATCH] kernel: kallsyms: parameters checking, for EXPORT_SYMBOL_GPL functions

[Chen Gang]

  for EXPORT_SYMBOL_GPL functions, necessary to check their parameters.

Signed-off-by: Chen Gang <gang.chen@asianux.com>
---
 kernel/kallsyms.c |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)

diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 2169fee..4ba57a9 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -175,6 +175,9 @@ unsigned long kallsyms_lookup_name(const char *name)
 	unsigned long i;
 	unsigned int off;
 
+	if (!name || !name[0])
+		return 0;
+
 	for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
 		off = kallsyms_expand_symbol(off, namebuf);
 
@@ -194,6 +197,9 @@ int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
 	unsigned int off;
 	int ret;
 
+	if (!fn)
+		return -EINVAL;
+
 	for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
 		off = kallsyms_expand_symbol(off, namebuf);
 		ret = fn(data, namebuf, NULL, kallsyms_addresses[i]);
@@ -382,6 +388,9 @@ static int __sprint_symbol(char *buffer, unsigned long address,
  */
 int sprint_symbol(char *buffer, unsigned long address)
 {
+	if (!buffer)
+		return 0;
+
 	return __sprint_symbol(buffer, address, 0, 1);
 }
 EXPORT_SYMBOL_GPL(sprint_symbol);
@@ -399,6 +408,9 @@ EXPORT_SYMBOL_GPL(sprint_symbol);
  */
 int sprint_symbol_no_offset(char *buffer, unsigned long address)
 {
+	if (!buffer)
+		return 0;
+
 	return __sprint_symbol(buffer, address, 0, 0);
 }
 EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
-- 
1.7.7.6

Re: [PATCH] kernel: kallsyms: parameters checking, for EXPORT_SYMBOL_GPL functions

[Rusty Russell]

Chen Gang <gang.chen@asianux.com> writes:
>   for EXPORT_SYMBOL_GPL functions, necessary to check their parameters.
>
> Signed-off-by: Chen Gang <gang.chen@asianux.com>

Why?

If someone misuses these functions, they crash and thus indicate that
the caller shouldn't do that.

Or is someone already doing this?

Confused,
Rusty.

> ---
>  kernel/kallsyms.c |   12 ++++++++++++
>  1 files changed, 12 insertions(+), 0 deletions(-)
>
> diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
> index 2169fee..4ba57a9 100644
> --- a/kernel/kallsyms.c
> +++ b/kernel/kallsyms.c
> @@ -175,6 +175,9 @@ unsigned long kallsyms_lookup_name(const char *name)
>  	unsigned long i;
>  	unsigned int off;
>  
> +	if (!name || !name[0])
> +		return 0;
> +
>  	for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
>  		off = kallsyms_expand_symbol(off, namebuf);
>  
> @@ -194,6 +197,9 @@ int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
>  	unsigned int off;
>  	int ret;
>  
> +	if (!fn)
> +		return -EINVAL;
> +
>  	for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
>  		off = kallsyms_expand_symbol(off, namebuf);
>  		ret = fn(data, namebuf, NULL, kallsyms_addresses[i]);
> @@ -382,6 +388,9 @@ static int __sprint_symbol(char *buffer, unsigned long address,
>   */
>  int sprint_symbol(char *buffer, unsigned long address)
>  {
> +	if (!buffer)
> +		return 0;
> +
>  	return __sprint_symbol(buffer, address, 0, 1);
>  }
>  EXPORT_SYMBOL_GPL(sprint_symbol);
> @@ -399,6 +408,9 @@ EXPORT_SYMBOL_GPL(sprint_symbol);
>   */
>  int sprint_symbol_no_offset(char *buffer, unsigned long address)
>  {
> +	if (!buffer)
> +		return 0;
> +
>  	return __sprint_symbol(buffer, address, 0, 0);
>  }
>  EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);
> -- 
> 1.7.7.6

Re: [PATCH] kernel: kallsyms: parameters checking, for EXPORT_SYMBOL_GPL functions

[Chen Gang]

On 2013年04月10日 14:57, Rusty Russell wrote:
> Chen Gang <gang.chen@asianux.com> writes:
>> >   for EXPORT_SYMBOL_GPL functions, necessary to check their parameters.
>> >
>> > Signed-off-by: Chen Gang <gang.chen@asianux.com>
> Why?
> 
> If someone misuses these functions, they crash and thus indicate that
> the caller shouldn't do that.
> 

  for me, I think:

    if it is used by self (such as static functions):
      I prefer to crash immediatly.
      it will help us to find issue, quickly.

    if it can be used by others (such as EXPORT_SYMBOL_GPL):
      I prefer to return fail and tell caller that parameter is invalid.
      it is more polite to callers, and still indicate it may be an issue.

  :-)


> Or is someone already doing this?
> 

  really has:

    kernel: __wake_up_sync_key in kernel/sched/core.c.
    lib: *printf.
    mm:  kfree.


> Confused,
> Rusty.
> 


-- 
Chen Gang

Asianux Corporation

Re: [PATCH] kernel: kallsyms: parameters checking, for EXPORT_SYMBOL_GPL functions

[Rusty Russell]

Chen Gang <gang.chen@asianux.com> writes:
> On 2013年04月10日 14:57, Rusty Russell wrote:
>> Chen Gang <gang.chen@asianux.com> writes:
>>> >   for EXPORT_SYMBOL_GPL functions, necessary to check their parameters.
>>> >
>>> > Signed-off-by: Chen Gang <gang.chen@asianux.com>
>> Why?
>> 
>> If someone misuses these functions, they crash and thus indicate that
>> the caller shouldn't do that.
>> 
>
>   for me, I think:
>
>     if it is used by self (such as static functions):
>       I prefer to crash immediatly.
>       it will help us to find issue, quickly.
>
>     if it can be used by others (such as EXPORT_SYMBOL_GPL):
>       I prefer to return fail and tell caller that parameter is invalid.
>       it is more polite to callers, and still indicate it may be an issue.
>
>   :-)

I disagree.  Calling with invalid parameters is a bug.  You've just
covered up some cases of invalid use and made it less likely to be
found.  Because the caller won't notice they screwed up.

We could sprinkle WARN_ON() everywhere, but I prefer the crash.  Even
harder to ignore.

There's no limit to how many of these checks we could put in, and we can
*never* take them out.  I don't want to code that way.

>> Or is someone already doing this?
>> 
>
>   really has:
>
>     kernel: __wake_up_sync_key in kernel/sched/core.c.
>     lib: *printf.
>     mm:  kfree.

No, I mean "is someone calling these functions with NULL".

Cheers,
Rusty.

Re: [PATCH] kernel: kallsyms: parameters checking, for EXPORT_SYMBOL_GPL functions

[Chen Gang]

On 2013年04月11日 10:52, Rusty Russell wrote:
>>> >> Or is someone already doing this?
>>> >> 
>> >
>> >   really has:
>> >
>> >     kernel: __wake_up_sync_key in kernel/sched/core.c.
>> >     lib: *printf.
>> >     mm:  kfree.
> No, I mean "is someone calling these functions with NULL".
> 
> Cheers,
> Rusty.
> 
> 

  often "kfree(NULL)", that is ok. it will let caller easier using it.
  also often give 0 size to snprintf, it still let caller easy using.

  if we treat EXPORT functions of kallsyms as commonly used (or we want to)
    I suggest to give parameter check for them.


  thanks.

  :-)

-- 
Chen Gang

Asianux Corporation