linux-kernel - [PATCH 5.8 421/633] ramfs: fix nommu mmap with gaps in the page cache

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Date:   Tue, 27 Oct 2020 14:52:44 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Howells <dhowells@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.8 421/633] ramfs: fix nommu mmap with gaps in the page cache

From: Matthew Wilcox (Oracle) <willy@...radead.org>

[ Upstream commit 50b7d85680086126d7bd91dae81d57d4cb1ab6b7 ]

ramfs needs to check that pages are both physically contiguous and
contiguous in the file.  If the page cache happens to have, eg, page A for
index 0 of the file, no page for index 1, and page A+1 for index 2, then
an mmap of the first two pages of the file will succeed when it should
fail.

Fixes: 642fb4d1f1dd ("[PATCH] NOMMU: Provide shared-writable mmap support on ramfs")
Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Cc: David Howells <dhowells@...hat.com>
Link: https://lkml.kernel.org/r/20200914122239.GO6583@casper.infradead.org
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/ramfs/file-nommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ramfs/file-nommu.c b/fs/ramfs/file-nommu.c
index 4146954549560..355523f4a4bf3 100644
--- a/fs/ramfs/file-nommu.c
+++ b/fs/ramfs/file-nommu.c
@@ -224,7 +224,7 @@ static unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
 	if (!pages)
 		goto out_free;
 
-	nr = find_get_pages(inode->i_mapping, &pgoff, lpages, pages);
+	nr = find_get_pages_contig(inode->i_mapping, pgoff, lpages, pages);
 	if (nr != lpages)
 		goto out_free_pages; /* leave if some pages were missing */
 
-- 
2.25.1