diff options
| author | Cosmin Tanislav | 2025-06-13 14:21:53 +0300 |
|---|---|---|
| committer | Hans Verkuil | 2025-06-23 12:11:04 +0200 |
| commit | c0b1da281d84d33281fc49289f0c7f8aada450ff (patch) | |
| tree | 32f753825180b5964eac960c798fd7162bd50d3f | |
| parent | 032a68ccb7834b28d51c11bbfe1c2db02e65ad28 (diff) | |
media: rc: ir-spi: avoid overflow in multiplication
Switch to u64 arithmetic and use DIV_ROUND_CLOSEST_ULL() to avoid
the overflow.
buffer[i] is unsigned int and is limited by the lirc core to
IR_MAX_DURATION, which is 500000.
idata->freq is u32, which has a max value of 0xFFFFFFFF.
In the case where buffer[i] is 500000, idata->freq overflows the u32
multiplication for any values >= 8590.
0xFFFFFFFF / 500000 ~= 8589
By casting buffer[i] to u64, idata->freq can be any u32 value without
overflowing the multiplication.
0xFFFFFFFFFFFFFFFF / 500000 ~= 36893488147419 (> 4294967295)
The result of the final operation will fit back into the unsigned int
limits without any issues.
500000 * 0xFFFFFFFF / 1000000 = 0x80000000 (< 0xFFFFFFFF)
Signed-off-by: Cosmin Tanislav <demonsingur@gmail.com>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
| -rw-r--r-- | drivers/media/rc/ir-spi.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/media/rc/ir-spi.c b/drivers/media/rc/ir-spi.c index 0b54ad74cec0..392441e0c116 100644 --- a/drivers/media/rc/ir-spi.c +++ b/drivers/media/rc/ir-spi.c @@ -46,7 +46,8 @@ static int ir_spi_tx(struct rc_dev *dev, unsigned int *buffer, unsigned int coun /* convert the pulse/space signal to raw binary signal */ for (i = 0; i < count; i++) { - buffer[i] = DIV_ROUND_CLOSEST(buffer[i] * idata->freq, 1000000); + buffer[i] = DIV_ROUND_CLOSEST_ULL((u64)buffer[i] * idata->freq, + 1000000); len += buffer[i]; } |