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    Subject[PATCH AUTOSEL 4.18 61/65] asm-generic: io: Fix ioport_map() for !CONFIG_GENERIC_IOMAP && CONFIG_INDIRECT_PIO
    Date
    From: Andrew Murray <andrew.murray@arm.com>

    [ Upstream commit 500dd232449e7c07500e713dc6970aa713f8e4f1 ]

    The !CONFIG_GENERIC_IOMAP version of ioport_map uses MMIO_UPPER_LIMIT to
    prevent users from making I/O accesses outside the expected I/O range -
    however it erroneously treats MMIO_UPPER_LIMIT as a mask which is
    contradictory to its other users.

    The introduction of CONFIG_INDIRECT_PIO, which subtracts an arbitrary
    amount from IO_SPACE_LIMIT to form MMIO_UPPER_LIMIT, results in ioport_map
    mangling the given port rather than capping it.

    We address this by aligning more closely with the CONFIG_GENERIC_IOMAP
    implementation of ioport_map by using the comparison operator and
    returning NULL where the port exceeds MMIO_UPPER_LIMIT. Though note that
    we preserve the existing behavior of masking with IO_SPACE_LIMIT such that
    we don't break existing buggy drivers that somehow rely on this masking.

    Fixes: 5745392e0c2b ("PCI: Apply the new generic I/O management on PCI IO hosts")
    Reported-by: Will Deacon <will.deacon@arm.com>
    Reviewed-by: Arnd Bergmann <arnd@arndb.de>
    Signed-off-by: Andrew Murray <andrew.murray@arm.com>
    Signed-off-by: Will Deacon <will.deacon@arm.com>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    ---
    include/asm-generic/io.h | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
    index 66d1d45fa2e1..d356f802945a 100644
    --- a/include/asm-generic/io.h
    +++ b/include/asm-generic/io.h
    @@ -1026,7 +1026,8 @@ static inline void __iomem *ioremap_wt(phys_addr_t offset, size_t size)
    #define ioport_map ioport_map
    static inline void __iomem *ioport_map(unsigned long port, unsigned int nr)
    {
    - return PCI_IOBASE + (port & MMIO_UPPER_LIMIT);
    + port &= IO_SPACE_LIMIT;
    + return (port > MMIO_UPPER_LIMIT) ? NULL : PCI_IOBASE + port;
    }
    #endif

    --
    2.17.1
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