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    Subject[PATCH AUTOSEL 5.4 20/40] media: mceusb: sanity check for prescaler value
    Date
    From: Sean Young <sean@mess.org>

    [ Upstream commit 9dec0f48a75e0dadca498002d25ef4e143e60194 ]

    prescaler larger than 8 would mean the carrier is at most 152Hz,
    which does not make sense for IR carriers.

    Reported-by: syzbot+6d31bf169a8265204b8d@syzkaller.appspotmail.com
    Signed-off-by: Sean Young <sean@mess.org>
    Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/media/rc/mceusb.c | 9 ++++++++-
    1 file changed, 8 insertions(+), 1 deletion(-)

    diff --git a/drivers/media/rc/mceusb.c b/drivers/media/rc/mceusb.c
    index f9616158bcf44..ca8995595c028 100644
    --- a/drivers/media/rc/mceusb.c
    +++ b/drivers/media/rc/mceusb.c
    @@ -701,11 +701,18 @@ static void mceusb_dev_printdata(struct mceusb_dev *ir, u8 *buf, int buf_len,
    data[0], data[1]);
    break;
    case MCE_RSP_EQIRCFS:
    + if (!data[0] && !data[1]) {
    + dev_dbg(dev, "%s: no carrier", inout);
    + break;
    + }
    + // prescaler should make sense
    + if (data[0] > 8)
    + break;
    period = DIV_ROUND_CLOSEST((1U << data[0] * 2) *
    (data[1] + 1), 10);
    if (!period)
    break;
    - carrier = (1000 * 1000) / period;
    + carrier = USEC_PER_SEC / period;
    dev_dbg(dev, "%s carrier of %u Hz (period %uus)",
    inout, carrier, period);
    break;
    --
    2.27.0
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