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    Subject[PATCH 4.9 074/121] mm/mmap.c: initialize align_offset explicitly for vm_unmapped_area
    Date
    From: Jaewon Kim <jaewon31.kim@samsung.com>

    [ Upstream commit 09ef5283fd96ac424ef0e569626f359bf9ab86c9 ]

    On passing requirement to vm_unmapped_area, arch_get_unmapped_area and
    arch_get_unmapped_area_topdown did not set align_offset. Internally on
    both unmapped_area and unmapped_area_topdown, if info->align_mask is 0,
    then info->align_offset was meaningless.

    But commit df529cabb7a2 ("mm: mmap: add trace point of
    vm_unmapped_area") always prints info->align_offset even though it is
    uninitialized.

    Fix this uninitialized value issue by setting it to 0 explicitly.

    Before:
    vm_unmapped_area: addr=0x755b155000 err=0 total_vm=0x15aaf0 flags=0x1 len=0x109000 lo=0x8000 hi=0x75eed48000 mask=0x0 ofs=0x4022

    After:
    vm_unmapped_area: addr=0x74a4ca1000 err=0 total_vm=0x168ab1 flags=0x1 len=0x9000 lo=0x8000 hi=0x753d94b000 mask=0x0 ofs=0x0

    Signed-off-by: Jaewon Kim <jaewon31.kim@samsung.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
    Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
    Cc: Michel Lespinasse <walken@google.com>
    Cc: Borislav Petkov <bp@suse.de>
    Link: http://lkml.kernel.org/r/20200409094035.19457-1-jaewon31.kim@samsung.com
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    mm/mmap.c | 2 ++
    1 file changed, 2 insertions(+)

    --- a/mm/mmap.c
    +++ b/mm/mmap.c
    @@ -2028,6 +2028,7 @@ arch_get_unmapped_area(struct file *filp
    info.low_limit = mm->mmap_base;
    info.high_limit = TASK_SIZE;
    info.align_mask = 0;
    + info.align_offset = 0;
    return vm_unmapped_area(&info);
    }
    #endif
    @@ -2069,6 +2070,7 @@ arch_get_unmapped_area_topdown(struct fi
    info.low_limit = max(PAGE_SIZE, mmap_min_addr);
    info.high_limit = mm->mmap_base;
    info.align_mask = 0;
    + info.align_offset = 0;
    addr = vm_unmapped_area(&info);

    /*

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