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    Subject[PATCH 5.9 511/757] ramfs: fix nommu mmap with gaps in the page cache
    Date
    From: Matthew Wilcox (Oracle) <willy@infradead.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@infradead.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Cc: David Howells <dhowells@redhat.com>
    Link: https://lkml.kernel.org/r/20200914122239.GO6583@casper.infradead.org
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.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


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