linux-kernel - [PATCH 5.13 198/223] mm: call flush_dcache_page() in memcpy_to_page() and memzero

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Date:   Mon, 26 Jul 2021 17:39:50 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Christoph Hellwig <hch@....de>,
        Ira Weiny <ira.weiny@...el.com>,
        Chaitanya Kulkarni <chaitanya.kulkarni@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 5.13 198/223] mm: call flush_dcache_page() in memcpy_to_page() and memzero_page()

From: Christoph Hellwig <hch@....de>

commit 8dad53a11f8d94dceb540a5f8f153484f42be84b upstream.

memcpy_to_page and memzero_page can write to arbitrary pages, which
could be in the page cache or in high memory, so call
flush_kernel_dcache_pages to flush the dcache.

This is a problem when using these helpers on dcache challeneged
architectures.  Right now there are just a few users, chances are no one
used the PC floppy driver, the aha1542 driver for an ISA SCSI HBA, and a
few advanced and optional btrfs and ext4 features on those platforms yet
since the conversion.

Link: https://lkml.kernel.org/r/20210713055231.137602-2-hch@lst.de
Fixes: bb90d4bc7b6a ("mm/highmem: Lift memcpy_[to|from]_page to core")
Fixes: 28961998f858 ("iov_iter: lift memzero_page() to highmem.h")
Signed-off-by: Christoph Hellwig <hch@....de>
Reviewed-by: Ira Weiny <ira.weiny@...el.com>
Cc: Chaitanya Kulkarni <chaitanya.kulkarni@....com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 include/linux/highmem.h |    2 ++
 1 file changed, 2 insertions(+)

--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -329,6 +329,7 @@ static inline void memcpy_to_page(struct
 
 	VM_BUG_ON(offset + len > PAGE_SIZE);
 	memcpy(to + offset, from, len);
+	flush_dcache_page(page);
 	kunmap_local(to);
 }
 
@@ -336,6 +337,7 @@ static inline void memzero_page(struct p
 {
 	char *addr = kmap_atomic(page);
 	memset(addr + offset, 0, len);
+	flush_dcache_page(page);
 	kunmap_atomic(addr);
 }