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    Subject[PATCH 4.20 109/183] atm: he: fix sign-extension overflow on large shift
    Date
    4.20-stable review patch.  If anyone has any objections, please let me know.

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

    [ Upstream commit cb12d72b27a6f41325ae23a11033cf5fedfa1b97 ]

    Shifting the 1 by exp by an int can lead to sign-extension overlow when
    exp is 31 since 1 is an signed int and sign-extending this result to an
    unsigned long long will set the upper 32 bits. Fix this by shifting an
    unsigned long.

    Detected by cppcheck:
    (warning) Shifting signed 32-bit value by 31 bits is undefined behaviour

    Signed-off-by: Colin Ian King <colin.king@canonical.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/atm/he.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/drivers/atm/he.c b/drivers/atm/he.c
    index 29f102dcfec49..329ce9072ee9f 100644
    --- a/drivers/atm/he.c
    +++ b/drivers/atm/he.c
    @@ -717,7 +717,7 @@ static int he_init_cs_block_rcm(struct he_dev *he_dev)
    instead of '/ 512', use '>> 9' to prevent a call
    to divdu3 on x86 platforms
    */
    - rate_cps = (unsigned long long) (1 << exp) * (man + 512) >> 9;
    + rate_cps = (unsigned long long) (1UL << exp) * (man + 512) >> 9;

    if (rate_cps < 10)
    rate_cps = 10; /* 2.2.1 minimum payload rate is 10 cps */
    --
    2.19.1


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