scsi: qla2xxx: Bound i2c->length in I2C bsg handlers

In the Linux kernel, the following vulnerability has been resolved: scsi: qla2xxx: Bound i2c->length in I2C bsg handlers struct qla_i2c_access carries a 16-bit length field alongside a fixed 64-byte buffer: struct qla_i2c_access { uint16_t device, offset, option, length; uint8_t buffer[0x40]; } __packed; qla2x00_write_i2c() and qla2x00_read_i2c() use the user-supplied i2c->length without any bounds check. i2c is overlaid on a 256-byte on-stack buffer and sfp is a 256-byte DMA-pool buffer, so a length up to 65535 overruns both: - write: memcpy(sfp, i2c->buffer, i2c->length) over-reads the stack and over-writes the sfp heap buffer, and qla2x00_write_sfp() then DMAs i2c->length bytes out of the 256-byte buffer. - read: qla2x00_read_sfp() DMAs i2c->length bytes into the 256-byte sfp, then memcpy(i2c->buffer, sfp, i2c->length) overflows the 64-byte buffer inside the on-stack array. A caller holding CAP_SYS_RAWIO can use this to corrupt the heap and the kernel stack. Reject requests whose length exceeds the buffer before any copy or DMA transfer in both handlers.