linux-kernel - Re: [PATCH] mm/mmap: undo ->mmap() when mas

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Message-ID: <20221018133917.i2fn5vqfwqntauvk@revolver>
Date:   Tue, 18 Oct 2022 13:39:35 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>
CC:     "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Lukas Bulwahn <lukas.bulwahn@...il.com>,
        Muchun Song <songmuchun@...edance.com>,
        Carlos Llamas <cmllamas@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] mm/mmap: undo ->mmap() when mas_preallocate() fails

This is for sure necessary.

Thanks Mike & Lukas.

Reviewed-by: Liam R. Howlett <Liam.Howlett@...cle.com>

* Mike Kravetz <mike.kravetz@...cle.com> [221017 22:49]:
> A memory leak in hugetlb_reserve_pages was reported in [1].  The root
> cause was traced to an error path in mmap_region when mas_preallocate()
> fails.  In this case, the vma is freed after a successful call to
> filesystem specific mmap.  The hugetlbfs mmap routine may allocate data
> structures pointed to by m_private_data.  These need to be cleaned up
> by the hugetlb vm_ops->close() routine.
> 
> The same issue was addressed by commit deb0f6562884 ("mm/mmap: undo
> ->mmap() when arch_validate_flags() fails") for the arch_validate_flags()
> test.  Go to the same close_and_free_vma label if mas_preallocate() fails.
> 
> [1] https://lore.kernel.org/linux-mm/CAKXUXMxf7OiCwbxib7MwfR4M1b5+b3cNTU7n5NV9Zm4967=FPQ@mail.gmail.com/
> 
> Fixes: d4af56c5c7c6 ("mm: start tracking VMAs with maple tree")
> Reported-by: Lukas Bulwahn <lukas.bulwahn@...il.com>
> Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
> ---
>  mm/mmap.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/mmap.c b/mm/mmap.c
> index bf2122af94e7..3c9890e443a3 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2681,7 +2681,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
>  	if (mas_preallocate(&mas, vma, GFP_KERNEL)) {
>  		error = -ENOMEM;
>  		if (file)
> -			goto unmap_and_free_vma;
> +			goto close_and_free_vma;
>  		else
>  			goto free_vma;
>  	}
> -- 
> 2.37.3
>