Re: [PATCH net-next] can: sja1000: fix use after free in ems_pcmcia_add_card()
From: Oliver Hartkopp <socketcan@hartkopp.net>
Date: 2021-11-23 20:42:37
Also in:
kernel-janitors, linux-can
Hello Dan, On 22.11.21 08:56, Dan Carpenter wrote:
In the original code if ems_pcmcia_check_chan() returned false then
it called free_sja1000dev(dev) but did not set the error code or jump
to the clean up code. This frees "dev" and leads to a use after free.
I flipped the ems_pcmcia_check_chan() check around to make the error
handling more consistent and readable. That lets us pull the rest of
the code in one tab.
Fixes: fd734c6f25ae ("can/sja1000: add driver for EMS PCMCIA card")
Signed-off-by: Dan Carpenter <redacted>
I do not think, that you are fixing something here.
The loop
for (i = 0; i < EMS_PCMCIA_MAX_CHAN; i++) { ...
checks with
if (ems_pcmcia_check_chan(priv))
whether this channel is 'available' or not.
As this hardware could come with only ONE channel it is just wrong to
tag a missing channel as error and finally kill the entire setup process
(including the potentially working channel we already initialized).
So thanks for the patch but NACK ;-)
Best regards,
Oliver
quoted hunk ↗ jump to hunk
--- drivers/net/can/sja1000/ems_pcmcia.c | 44 +++++++++++++++------------- 1 file changed, 23 insertions(+), 21 deletions(-)diff --git a/drivers/net/can/sja1000/ems_pcmcia.c b/drivers/net/can/sja1000/ems_pcmcia.c index e21b169c14c0..271fe9444827 100644 --- a/drivers/net/can/sja1000/ems_pcmcia.c +++ b/drivers/net/can/sja1000/ems_pcmcia.c@@ -210,28 +210,30 @@ static int ems_pcmcia_add_card(struct pcmcia_device *pdev, unsigned long base) (i * EMS_PCMCIA_CAN_CTRL_SIZE); /* Check if channel is present */ - if (ems_pcmcia_check_chan(priv)) { - priv->read_reg = ems_pcmcia_read_reg; - priv->write_reg = ems_pcmcia_write_reg; - priv->can.clock.freq = EMS_PCMCIA_CAN_CLOCK; - priv->ocr = EMS_PCMCIA_OCR; - priv->cdr = EMS_PCMCIA_CDR; - priv->flags |= SJA1000_CUSTOM_IRQ_HANDLER; - - /* Register SJA1000 device */ - err = register_sja1000dev(dev); - if (err) { - free_sja1000dev(dev); - goto failure_cleanup; - } - - card->channels++; - - printk(KERN_INFO "%s: registered %s on channel " - "#%d at 0x%p, irq %d\n", DRV_NAME, dev->name, - i, priv->reg_base, dev->irq); - } else + if (!ems_pcmcia_check_chan(priv)) { + err = -EINVAL; free_sja1000dev(dev); + goto failure_cleanup; + } + priv->read_reg = ems_pcmcia_read_reg; + priv->write_reg = ems_pcmcia_write_reg; + priv->can.clock.freq = EMS_PCMCIA_CAN_CLOCK; + priv->ocr = EMS_PCMCIA_OCR; + priv->cdr = EMS_PCMCIA_CDR; + priv->flags |= SJA1000_CUSTOM_IRQ_HANDLER; + + /* Register SJA1000 device */ + err = register_sja1000dev(dev); + if (err) { + free_sja1000dev(dev); + goto failure_cleanup; + } + + card->channels++; + + printk(KERN_INFO "%s: registered %s on channel " + "#%d at 0x%p, irq %d\n", DRV_NAME, dev->name, + i, priv->reg_base, dev->irq); } err = request_irq(dev->irq, &ems_pcmcia_interrupt, IRQF_SHARED,