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    Subject[PATCH 4.4 30/85] mm: pagewalk: fix termination condition in walk_pte_range()
    Date
    From: Steven Price <steven.price@arm.com>

    [ Upstream commit c02a98753e0a36ba65a05818626fa6adeb4e7c97 ]

    If walk_pte_range() is called with a 'end' argument that is beyond the
    last page of memory (e.g. ~0UL) then the comparison between 'addr' and
    'end' will always fail and the loop will be infinite. Instead change the
    comparison to >= while accounting for overflow.

    Link: http://lkml.kernel.org/r/20191218162402.45610-15-steven.price@arm.com
    Signed-off-by: Steven Price <steven.price@arm.com>
    Cc: Albert Ou <aou@eecs.berkeley.edu>
    Cc: Alexandre Ghiti <alex@ghiti.fr>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
    Cc: Arnd Bergmann <arnd@arndb.de>
    Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Catalin Marinas <catalin.marinas@arm.com>
    Cc: Christian Borntraeger <borntraeger@de.ibm.com>
    Cc: Dave Hansen <dave.hansen@linux.intel.com>
    Cc: David S. Miller <davem@davemloft.net>
    Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
    Cc: "H. Peter Anvin" <hpa@zytor.com>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: James Hogan <jhogan@kernel.org>
    Cc: James Morse <james.morse@arm.com>
    Cc: Jerome Glisse <jglisse@redhat.com>
    Cc: "Liang, Kan" <kan.liang@linux.intel.com>
    Cc: Mark Rutland <mark.rutland@arm.com>
    Cc: Michael Ellerman <mpe@ellerman.id.au>
    Cc: Paul Burton <paul.burton@mips.com>
    Cc: Paul Mackerras <paulus@samba.org>
    Cc: Paul Walmsley <paul.walmsley@sifive.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Ralf Baechle <ralf@linux-mips.org>
    Cc: Russell King <linux@armlinux.org.uk>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Vasily Gorbik <gor@linux.ibm.com>
    Cc: Vineet Gupta <vgupta@synopsys.com>
    Cc: Will Deacon <will@kernel.org>
    Cc: Zong Li <zong.li@sifive.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    mm/pagewalk.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/mm/pagewalk.c b/mm/pagewalk.c
    index c2cbd26201696..a024667a9c041 100644
    --- a/mm/pagewalk.c
    +++ b/mm/pagewalk.c
    @@ -14,9 +14,9 @@ static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
    err = walk->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
    if (err)
    break;
    - addr += PAGE_SIZE;
    - if (addr == end)
    + if (addr >= end - PAGE_SIZE)
    break;
    + addr += PAGE_SIZE;
    pte++;
    }

    --
    2.25.1


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