[PATCH v2] mm: initialize return of vm_insert_pages

[PATCH v2] mm: initialize return of vm_insert_pages

[trix]

From: Tom Rix <trix@redhat.com>

clang static analysis reports a garbage return

In file included from mm/memory.c:84:
mm/memory.c:1612:2: warning: Undefined or garbage value returned to caller [core.uninitialized.UndefReturn]
        return err;
        ^~~~~~~~~~

The setting of err depends on a loop executing.
So initialize err.

Signed-off-by: Tom Rix <trix@redhat.com>
---
v1 change err intializer to -EINVAL

 mm/memory.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memory.c b/mm/memory.c
index 17a3df0f3994..76a00f414777 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1601,7 +1601,7 @@ int vm_insert_pages(struct vm_area_struct *vma, unsigned long addr,
 	return insert_pages(vma, addr, pages, num, vma->vm_page_prot);
 #else
 	unsigned long idx = 0, pgcount = *num;
-	int err;
+	int err = -EINVAL;
 
 	for (; idx < pgcount; ++idx) {
 		err = vm_insert_page(vma, addr + (PAGE_SIZE * idx), pages[idx]);
-- 
2.18.1

Re: [PATCH v2] mm: initialize return of vm_insert_pages

[Andrew Morton]

On Fri,  3 Jul 2020 08:53:54 -0700 trix@redhat.com wrote:

> From: Tom Rix <trix@redhat.com>
> 
> clang static analysis reports a garbage return
> 
> In file included from mm/memory.c:84:
> mm/memory.c:1612:2: warning: Undefined or garbage value returned to caller [core.uninitialized.UndefReturn]
>         return err;
>         ^~~~~~~~~~
> 
> The setting of err depends on a loop executing.
> So initialize err.
>
> ...
>
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1601,7 +1601,7 @@ int vm_insert_pages(struct vm_area_struct *vma, unsigned long addr,
>  	return insert_pages(vma, addr, pages, num, vma->vm_page_prot);
>  #else
>  	unsigned long idx = 0, pgcount = *num;
> -	int err;
> +	int err = -EINVAL;
>  
>  	for (; idx < pgcount; ++idx) {
>  		err = vm_insert_page(vma, addr + (PAGE_SIZE * idx), pages[idx]);

If a caller were to ask vm_insert_pages() to insert zero pages, I
suspect we should just return zero and set *num to zero.

Re: [PATCH v2] mm: initialize return of vm_insert_pages

[Tom Rix]

On 7/3/20 12:04 PM, Andrew Morton wrote:
> On Fri,  3 Jul 2020 08:53:54 -0700 trix@redhat.com wrote:
>
>> From: Tom Rix <trix@redhat.com>
>>
>> clang static analysis reports a garbage return
>>
>> In file included from mm/memory.c:84:
>> mm/memory.c:1612:2: warning: Undefined or garbage value returned to caller [core.uninitialized.UndefReturn]
>>         return err;
>>         ^~~~~~~~~~
>>
>> The setting of err depends on a loop executing.
>> So initialize err.
>>
>> ...
>>
>> --- a/mm/memory.c
>> +++ b/mm/memory.c
>> @@ -1601,7 +1601,7 @@ int vm_insert_pages(struct vm_area_struct *vma, unsigned long addr,
>>  	return insert_pages(vma, addr, pages, num, vma->vm_page_prot);
>>  #else
>>  	unsigned long idx = 0, pgcount = *num;
>> -	int err;
>> +	int err = -EINVAL;
>>  
>>  	for (; idx < pgcount; ++idx) {
>>  		err = vm_insert_page(vma, addr + (PAGE_SIZE * idx), pages[idx]);
> If a caller were to ask vm_insert_pages() to insert zero pages, I
> suspect we should just return zero and set *num to zero.

That would be v1 of the patch.

For the loop to not execute *num/pgcount is initially 0, and *num = pgcount - idx is 0 on exit.

 

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