linux-kernel - Re: [PATCH v1 13/16] mm: Don't skip arch_sync_kernel

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Message-ID: <15660c4c-5c4d-4229-b5c5-abcabd402058@arm.com>
Date: Fri, 7 Feb 2025 15:51:37 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Ryan Roberts <ryan.roberts@....com>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Muchun Song <muchun.song@...ux.dev>,
 Pasha Tatashin <pasha.tatashin@...een.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Uladzislau Rezki <urezki@...il.com>, Christoph Hellwig <hch@...radead.org>,
 Mark Rutland <mark.rutland@....com>, Ard Biesheuvel <ardb@...nel.org>,
 Dev Jain <dev.jain@....com>, Alexandre Ghiti <alexghiti@...osinc.com>,
 Steve Capper <steve.capper@...aro.org>, Kevin Brodsky <kevin.brodsky@....com>
Cc: linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v1 13/16] mm: Don't skip arch_sync_kernel_mappings() in
 error paths



On 2/5/25 20:39, Ryan Roberts wrote:
> Fix callers that previously skipped calling arch_sync_kernel_mappings()
> if an error occurred during a pgtable update. The call is still required
> to sync any pgtable updates that may have occurred prior to hitting the
> error condition.
> 
> These are theoretical bugs discovered during code review.
> 
> Cc: <stable@...r.kernel.org>
> Fixes: 2ba3e6947aed ("mm/vmalloc: track which page-table levels were modified")
> Fixes: 0c95cba49255 ("mm: apply_to_pte_range warn and fail if a large pte is encountered")
> Signed-off-by: Ryan Roberts <ryan.roberts@....com>

This change could stand on its own and LGTM.

Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>

> ---
>  mm/memory.c  | 6 ++++--
>  mm/vmalloc.c | 4 ++--
>  2 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index 539c0f7c6d54..a15f7dd500ea 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3040,8 +3040,10 @@ static int __apply_to_page_range(struct mm_struct *mm, unsigned long addr,
>  		next = pgd_addr_end(addr, end);
>  		if (pgd_none(*pgd) && !create)
>  			continue;
> -		if (WARN_ON_ONCE(pgd_leaf(*pgd)))
> -			return -EINVAL;
> +		if (WARN_ON_ONCE(pgd_leaf(*pgd))) {
> +			err = -EINVAL;
> +			break;
> +		}
>  		if (!pgd_none(*pgd) && WARN_ON_ONCE(pgd_bad(*pgd))) {
>  			if (!create)
>  				continue;
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 6111ce900ec4..68950b1824d0 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -604,13 +604,13 @@ static int vmap_small_pages_range_noflush(unsigned long addr, unsigned long end,
>  			mask |= PGTBL_PGD_MODIFIED;
>  		err = vmap_pages_p4d_range(pgd, addr, next, prot, pages, &nr, &mask);
>  		if (err)
> -			return err;
> +			break;
>  	} while (pgd++, addr = next, addr != end);
>  
>  	if (mask & ARCH_PAGE_TABLE_SYNC_MASK)
>  		arch_sync_kernel_mappings(start, end);
>  
> -	return 0;
> +	return err;
>  }
>  
>  /*