Re: [PATCH 1/3] ima: Remove inode lock

["Kirill A. Shutemov" <kirill@shutemov.name>]

On Fri, Oct 18, 2024 at 01:49:21PM +0300, Kirill A. Shutemov wrote:
> On Fri, Oct 18, 2024 at 11:24:06AM +0200, Roberto Sassu wrote:
> > Probably it is hard, @Kirill would there be any way to safely move
> > security_mmap_file() out of the mmap_lock lock?
> 
> What about something like this (untested):
> 
> diff --git a/mm/mmap.c b/mm/mmap.c
> index dd4b35a25aeb..03473e77d356 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1646,6 +1646,26 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
>  	if (pgoff + (size >> PAGE_SHIFT) < pgoff)
>  		return ret;
>  
> +	if (mmap_read_lock_killable(mm))
> +		return -EINTR;
> +
> +	vma = vma_lookup(mm, start);
> +
> +	if (!vma || !(vma->vm_flags & VM_SHARED)) {
> +		mmap_read_unlock(mm);
> +		return -EINVAL;
> +	}
> +
> +	file = get_file(vma->vm_file);
> +
> +	mmap_read_unlock(mm);
> +
> +	ret = security_mmap_file(vma->vm_file, prot, flags);
> +	if (ret) {
> +		fput(file);
> +		return ret;
> +	}
> +

Emm. We need to restore 'ret' to -EINVAL here:

+ 
+  	ret = -EINVAL;
+ 

>  	if (mmap_write_lock_killable(mm))
>  		return -EINTR;
>  
> @@ -1654,6 +1674,9 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
>  	if (!vma || !(vma->vm_flags & VM_SHARED))
>  		goto out;
>  
> +	if (vma->vm_file != file)
> +		goto out;
> +
>  	if (start + size > vma->vm_end) {
>  		VMA_ITERATOR(vmi, mm, vma->vm_end);
>  		struct vm_area_struct *next, *prev = vma;
> @@ -1688,16 +1711,11 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
>  	if (vma->vm_flags & VM_LOCKED)
>  		flags |= MAP_LOCKED;
>  
> -	file = get_file(vma->vm_file);
> -	ret = security_mmap_file(vma->vm_file, prot, flags);
> -	if (ret)
> -		goto out_fput;
>  	ret = do_mmap(vma->vm_file, start, size,
>  			prot, flags, 0, pgoff, &populate, NULL);
> -out_fput:
> -	fput(file);
>  out:
>  	mmap_write_unlock(mm);
> +	fput(file);
>  	if (populate)
>  		mm_populate(ret, populate);
>  	if (!IS_ERR_VALUE(ret))
> -- 
>   Kiryl Shutsemau / Kirill A. Shutemov

-- 
  Kiryl Shutsemau / Kirill A. Shutemov