Subject: Re: [PATCH 1/1 net-next] net: dsa: replace count*size kmalloc by kmalloc_array

From: Joe Perches <[email-masked]>
Date: Fri, 14 Nov 2014 10:47:15 -0800

On Fri, 2014-11-14 at 19:36 +0100, Fabian Frederick wrote:
> kmalloc_array manages count*sizeof overflow.

Fundamentally correct, but is this necessary or useful?
sizeof(s8) isn't often going to be anything other than 1.

Would the kernel even work without that assumption?

> diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
[]
> @@ -526,7 +526,8 @@ static int dsa_of_setup_routing_table(struct dsa_platform_data *pd,
>  
>  	/* First time routing table allocation */
>  	if (!cd->rtable) {
> -		cd->rtable = kmalloc(pd->nr_chips * sizeof(s8), GFP_KERNEL);
> +		cd->rtable = kmalloc_array(pd->nr_chips, sizeof(s8),
> +					   GFP_KERNEL);
>  		if (!cd->rtable)
>  			return -ENOMEM;
>  

Maybe all of these could be simplified

$ git grep -E "\*\s*sizeof\s*\(\s*[us]8\s*\)"
arch/arm/common/edma.c:                                   (edma_cc->num_tc + 1) * sizeof(s8),
drivers/acpi/utils.c:                               (element->buffer.length * sizeof(u8));
drivers/acpi/utils.c:                           tail += element->buffer.length * sizeof(u8);
drivers/char/tpm/tpm_i2c_stm_st33.c:        kmalloc(TPM_BUFSIZE * sizeof(u8), GFP_KERNEL);
drivers/char/tpm/tpm_i2c_stm_st33.c:        kmalloc(TPM_BUFSIZE * sizeof(u8), GFP_KERNEL);
drivers/gpu/drm/r128/r128_state.c:      mask_size = depth->n * sizeof(u8);
drivers/gpu/drm/r128/r128_state.c:              mask_size = depth->n * sizeof(u8);
drivers/iio/common/st_sensors/st_sensors_spi.c: memcpy(data, tb->rx_buf, len*sizeof(u8));
drivers/infiniband/hw/amso1100/c2_mq.h: u8 pad[64 - sizeof(u16) - 2 * sizeof(u8) - sizeof(u32) - sizeof(u16)];
drivers/input/tablet/aiptek.c:  const int sizeof_buf = 3 * sizeof(u8);
drivers/input/tablet/aiptek.c:  const int sizeof_buf = 3 * sizeof(u8);
drivers/md/dm-crypt.c:  memset(&cc->key, 0, cc->key_size * sizeof(u8));
drivers/md/dm-crypt.c:  cc = kzalloc(sizeof(*cc) + key_size * sizeof(u8), GFP_KERNEL);
drivers/media/dvb-frontends/dib7000p.c: tx = kzalloc(2*sizeof(u8), GFP_KERNEL);
drivers/media/dvb-frontends/dib7000p.c: rx = kzalloc(2*sizeof(u8), GFP_KERNEL);
drivers/media/dvb-frontends/dib8000.c:  client.i2c_write_buffer = kzalloc(4 * sizeof(u8), GFP_KERNEL);
drivers/media/dvb-frontends/dib8000.c:  client.i2c_read_buffer = kzalloc(4 * sizeof(u8), GFP_KERNEL);
drivers/media/dvb-frontends/dib9000.c:  client.i2c_write_buffer = kzalloc(4 * sizeof(u8), GFP_KERNEL);
drivers/media/dvb-frontends/dib9000.c:  client.i2c_read_buffer = kzalloc(4 * sizeof(u8), GFP_KERNEL);
drivers/media/pci/ttpci/av7110_ipack.c: if (!(p->buf = vmalloc(size*sizeof(u8)))) {
drivers/mtd/inftlmount.c:                               s->nb_blocks * sizeof(u8));
drivers/net/wireless/ath/ath10k/htt.h:   *  b) num_chars * sizeof(u8) aligned to 4bytes */
drivers/net/wireless/b43/ppr.c: BUILD_BUG_ON(sizeof(struct b43_ppr) != B43_PPR_RATES_NUM * sizeof(u8));
drivers/net/wireless/iwlwifi/pcie/trans.c:                     trans_pcie->n_no_reclaim_cmds * sizeof(u8));
drivers/net/wireless/rtlwifi/efuse.c:   memset(data, 0xff, PGPKT_DATA_SIZE * sizeof(u8));
drivers/net/wireless/rtlwifi/efuse.c:   memset(tmpdata, 0xff, PGPKT_DATA_SIZE * sizeof(u8));
drivers/net/wireless/rtlwifi/efuse.c:   u8 originaldata[8 * sizeof(u8)];
drivers/net/wireless/rtlwifi/efuse.c:   u8 originaldata[8 * sizeof(u8)];
drivers/net/wireless/rtlwifi/efuse.c:           memset(originaldata, 0xff,  8 * sizeof(u8));
drivers/net/wireless/rtlwifi/efuse.c:   memset(target_pkt.data, 0xFF,  8 * sizeof(u8));
drivers/power/ds2781_battery.c: ret = w1_ds2781_read(dev_info, val, DS2781_VOLT_MSB, 2 * sizeof(u8));
drivers/power/ds2781_battery.c: ret = w1_ds2781_read(dev_info, val, DS2781_TEMP_MSB, 2 * sizeof(u8));
drivers/rtc/rtc-pcf2123.c:      ret = spi_write(spi, txbuf, 2 * sizeof(u8));
drivers/rtc/rtc-pcf2123.c:      ret = spi_write(spi, txbuf, 2 * sizeof(u8));
drivers/rtc/rtc-pcf2123.c:      ret = spi_write_then_read(spi, txbuf, 1 * sizeof(u8),
drivers/rtc/rtc-pcf2123.c:                                      rxbuf, 2 * sizeof(u8));
drivers/thermal/x86_pkg_temp_thermal.c:                 (max_phy_id+1) * sizeof(u8), GFP_ATOMIC);
fs/compat_ioctl.c:      if (__copy_in_user(&tdata->read_write, &udata->read_write, 2 * sizeof(u8)))
net/dsa/dsa.c:          cd->rtable = kmalloc(pd->nr_chips * sizeof(s8), GFP_KERNEL);
net/dsa/dsa.c:          memset(cd->rtable, -1, pd->nr_chips * sizeof(s8));