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    Subject[PATCH 3.13 029/103] MIPS: OCTEON: make get_system_type() thread-safe
    Date
    3.13.11.8 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Aaro Koskinen <aaro.koskinen@nsn.com>

    commit 608308682addfdc7b8e2aee88f0e028331d88e4d upstream.

    get_system_type() is not thread-safe on OCTEON. It uses static data,
    also more dangerous issue is that it's calling cvmx_fuse_read_byte()
    every time without any synchronization. Currently it's possible to get
    processes stuck looping forever in kernel simply by launching multiple
    readers of /proc/cpuinfo:

    (while true; do cat /proc/cpuinfo > /dev/null; done) &
    (while true; do cat /proc/cpuinfo > /dev/null; done) &
    ...

    Fix by initializing the system type string only once during the early
    boot.

    Signed-off-by: Aaro Koskinen <aaro.koskinen@nsn.com>
    Reviewed-by: Markos Chandras <markos.chandras@imgtec.com>
    Patchwork: http://patchwork.linux-mips.org/patch/7437/
    Signed-off-by: James Hogan <james.hogan@imgtec.com>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    arch/mips/cavium-octeon/setup.c | 18 +++++++++++++-----
    1 file changed, 13 insertions(+), 5 deletions(-)

    diff --git a/arch/mips/cavium-octeon/setup.c b/arch/mips/cavium-octeon/setup.c
    index 331b837..270cb3c 100644
    --- a/arch/mips/cavium-octeon/setup.c
    +++ b/arch/mips/cavium-octeon/setup.c
    @@ -458,6 +458,18 @@ static void octeon_halt(void)
    octeon_kill_core(NULL);
    }

    +static char __read_mostly octeon_system_type[80];
    +
    +static int __init init_octeon_system_type(void)
    +{
    + snprintf(octeon_system_type, sizeof(octeon_system_type), "%s (%s)",
    + cvmx_board_type_to_string(octeon_bootinfo->board_type),
    + octeon_model_get_string(read_c0_prid()));
    +
    + return 0;
    +}
    +early_initcall(init_octeon_system_type);
    +
    /**
    * Return a string representing the system type
    *
    @@ -465,11 +477,7 @@ static void octeon_halt(void)
    */
    const char *octeon_board_type_string(void)
    {
    - static char name[80];
    - sprintf(name, "%s (%s)",
    - cvmx_board_type_to_string(octeon_bootinfo->board_type),
    - octeon_model_get_string(read_c0_prid()));
    - return name;
    + return octeon_system_type;
    }

    const char *get_system_type(void)
    --
    1.9.1


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