[PATCH] parisc: mm: Fix a memory leak related to pmd not attached to the pgd

[PATCH] parisc: mm: Fix a memory leak related to pmd not attached to the pgd

[Christophe JAILLET]

Commit 0e0da48dee8d ("parisc: mm: don't count preallocated pmds")
introduced a memory leak.

After this commit, the 'return' statement in pmd_free is executed in all
cases. Even for pmd that are not attached to the pgd.
So 'free_pages' can never be called anymore, leading to a memory leak.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
This patch is *untested* as I don't have the hardware to test it.

This is just a guess based on the indentation, the comment in the code
and the commit log.
---
 arch/parisc/include/asm/pgalloc.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/parisc/include/asm/pgalloc.h b/arch/parisc/include/asm/pgalloc.h
index 3a08eae..f66d3738 100644
--- a/arch/parisc/include/asm/pgalloc.h
+++ b/arch/parisc/include/asm/pgalloc.h
@@ -72,7 +72,7 @@ static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long address)
 
 static inline void pmd_free(struct mm_struct *mm, pmd_t *pmd)
 {
-	if(pmd_flag(*pmd) & PxD_FLAG_ATTACHED)
+	if (pmd_flag(*pmd) & PxD_FLAG_ATTACHED) {
 		/*
 		 * This is the permanent pmd attached to the pgd;
 		 * cannot free it.
@@ -81,6 +81,7 @@ static inline void pmd_free(struct mm_struct *mm, pmd_t *pmd)
 		 */
 		mm_inc_nr_pmds(mm);
 		return;
+	}
 	free_pages((unsigned long)pmd, PMD_ORDER);
 }
 
-- 
2.1.4

RE: [PATCH] parisc: mm: Fix a memory leak related to pmd not attached to the pgd

[Kirill A. Shutemov]

Christophe JAILLET wrote:
> Commit 0e0da48dee8d ("parisc: mm: don't count preallocated pmds")
> introduced a memory leak.
> 
> After this commit, the 'return' statement in pmd_free is executed in all
> cases. Even for pmd that are not attached to the pgd.
> So 'free_pages' can never be called anymore, leading to a memory leak.
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

> ---
> This patch is *untested* as I don't have the hardware to test it.
> 
> This is just a guess based on the indentation, the comment in the code
> and the commit log.
> ---
>  arch/parisc/include/asm/pgalloc.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/parisc/include/asm/pgalloc.h b/arch/parisc/include/asm/pgalloc.h
> index 3a08eae..f66d3738 100644
> --- a/arch/parisc/include/asm/pgalloc.h
> +++ b/arch/parisc/include/asm/pgalloc.h
> @@ -72,7 +72,7 @@ static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long address)
>  
>  static inline void pmd_free(struct mm_struct *mm, pmd_t *pmd)
>  {
> -	if(pmd_flag(*pmd) & PxD_FLAG_ATTACHED)
> +	if (pmd_flag(*pmd) & PxD_FLAG_ATTACHED) {
>  		/*
>  		 * This is the permanent pmd attached to the pgd;
>  		 * cannot free it.
> @@ -81,6 +81,7 @@ static inline void pmd_free(struct mm_struct *mm, pmd_t *pmd)
>  		 */
>  		mm_inc_nr_pmds(mm);
>  		return;
> +	}
>  	free_pages((unsigned long)pmd, PMD_ORDER);
>  }
>  
> -- 
> 2.1.4
> 

Re: [PATCH] parisc: mm: Fix a memory leak related to pmd not attached to the pgd

[Mikulas Patocka]

On Mon, 13 Jul 2015, Christophe JAILLET wrote:

> Commit 0e0da48dee8d ("parisc: mm: don't count preallocated pmds")
> introduced a memory leak.
> 
> After this commit, the 'return' statement in pmd_free is executed in all
> cases. Even for pmd that are not attached to the pgd.
> So 'free_pages' can never be called anymore, leading to a memory leak.
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>

Acked-by: Mikulas Patocka <mpatocka@redhat.com>

also add this, so that it is backported to 4.0 and 4.2:
Cc: stable@vger.kernel.org	# 4.0+
Fixes: 0e0da48dee8d

> ---
> This patch is *untested* as I don't have the hardware to test it.
> 
> This is just a guess based on the indentation, the comment in the code
> and the commit log.
> ---
>  arch/parisc/include/asm/pgalloc.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/parisc/include/asm/pgalloc.h b/arch/parisc/include/asm/pgalloc.h
> index 3a08eae..f66d3738 100644
> --- a/arch/parisc/include/asm/pgalloc.h
> +++ b/arch/parisc/include/asm/pgalloc.h
> @@ -72,7 +72,7 @@ static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long address)
>  
>  static inline void pmd_free(struct mm_struct *mm, pmd_t *pmd)
>  {
> -	if(pmd_flag(*pmd) & PxD_FLAG_ATTACHED)
> +	if (pmd_flag(*pmd) & PxD_FLAG_ATTACHED) {
>  		/*
>  		 * This is the permanent pmd attached to the pgd;
>  		 * cannot free it.
> @@ -81,6 +81,7 @@ static inline void pmd_free(struct mm_struct *mm, pmd_t *pmd)
>  		 */
>  		mm_inc_nr_pmds(mm);
>  		return;
> +	}
>  	free_pages((unsigned long)pmd, PMD_ORDER);
>  }
>  
> -- 
> 2.1.4
> 

Re: [PATCH] parisc: mm: Fix a memory leak related to pmd not attached to the pgd

[Helge Deller]

Hi Christophe,

On 13.07.2015 11:32, Christophe JAILLET wrote:
> Commit 0e0da48dee8d ("parisc: mm: don't count preallocated pmds")
> introduced a memory leak.
>
> After this commit, the 'return' statement in pmd_free is executed in all
> cases. Even for pmd that are not attached to the pgd.
> So 'free_pages' can never be called anymore, leading to a memory leak.

That's really great!!! Thanks for spotting this!

I assume this fixes the leak which killed our debian buildds with OOM
after an uptime of 1-4 days and which only happened since kernel 4.0.
Meelis Roos reported the issue already in this thread:
http://marc.info/?l=linux-parisc&m\x142999113232154&w=2

> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>

Acked-by: Helge Deller <deller@gmx.de>


Will this patch be pushed via linux-mm or another tree, if
not I can take it via the parisc tree?


Helge


> ---
> This patch is *untested* as I don't have the hardware to test it.
>
> This is just a guess based on the indentation, the comment in the code
> and the commit log.
> ---
>   arch/parisc/include/asm/pgalloc.h | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/parisc/include/asm/pgalloc.h b/arch/parisc/include/asm/pgalloc.h
> index 3a08eae..f66d3738 100644
> --- a/arch/parisc/include/asm/pgalloc.h
> +++ b/arch/parisc/include/asm/pgalloc.h
> @@ -72,7 +72,7 @@ static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long address)
>
>   static inline void pmd_free(struct mm_struct *mm, pmd_t *pmd)
>   {
> -	if(pmd_flag(*pmd) & PxD_FLAG_ATTACHED)
> +	if (pmd_flag(*pmd) & PxD_FLAG_ATTACHED) {
>   		/*
>   		 * This is the permanent pmd attached to the pgd;
>   		 * cannot free it.
> @@ -81,6 +81,7 @@ static inline void pmd_free(struct mm_struct *mm, pmd_t *pmd)
>   		 */
>   		mm_inc_nr_pmds(mm);
>   		return;
> +	}
>   	free_pages((unsigned long)pmd, PMD_ORDER);
>   }
>
>

Re: [PATCH] parisc: mm: Fix a memory leak related to pmd not attached to the pgd

[Dan Carpenter]

I assume you found this with Coccinelle?  Smatch can also find this bug
but you would need a cross compile environment set up.

regards,
dan carpenter

Re: [PATCH] parisc: mm: Fix a memory leak related to pmd not attached to the pgd

[Meelis Roos]

> Hi Christophe,
> 
> On 13.07.2015 11:32, Christophe JAILLET wrote:
> > Commit 0e0da48dee8d ("parisc: mm: don't count preallocated pmds")
> > introduced a memory leak.
> >
> > After this commit, the 'return' statement in pmd_free is executed in all
> > cases. Even for pmd that are not attached to the pgd.
> > So 'free_pages' can never be called anymore, leading to a memory leak.
> 
> That's really great!!! Thanks for spotting this!
> 
> I assume this fixes the leak which killed our debian buildds with OOM
> after an uptime of 1-4 days and which only happened since kernel 4.0.
> Meelis Roos reported the issue already in this thread:
> http://marc.info/?l=linux-parisc&m\x142999113232154&w=2

Yes, the patch that is merged in 4.2-rc3 fixed my RP3410 with 1G RAM.

-- 
Meelis Roos (mroos@linux.ee)