Messages in this thread | | | Date | Fri, 24 Jul 2009 12:40:28 -0500 | Subject | Re: FW: [PATCH] cs5535_gpio: Fix root triggerable integer underflow | From | Ben Gardner <> |
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Hi Michael,
> This patch fixes a possible root triggerable (I hope the device is only > readable by root?) integer underflow. > Well, it's not really an underflow, but as loff_t is a signed type, the > range check at the start of the function is incomplete. It needs to > check for <0, too. > Otherwise the loop below will poke into random memory and I/O space. > This could be used to crash the machine, at least. > > This patch is only compiletested, because I do not have the hardware. > > Signed-off-by: Michael Buesch <mb@bu3sch.de> > > --- > > I'm not sure if this bug is exploitable. I _guess_ the device is only > readable by root > on a standard setup.
The cs5525_gpio driver uses the default seek, which doesn't allow negative position values. So, I don't think it necessary to check for negative values.
Ben
> --- > drivers/char/cs5535_gpio.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > --- linux-2.6.orig/drivers/char/cs5535_gpio.c > +++ linux-2.6/drivers/char/cs5535_gpio.c > @@ -124,21 +124,21 @@ static ssize_t cs5535_gpio_write(struct > static ssize_t cs5535_gpio_read(struct file *file, char __user *buf, > size_t len, loff_t *ppos) > { > u32 m = iminor(file->f_path.dentry->d_inode); > u32 base = gpio_base + cs5535_lowhigh_base(m); > int rd_bit = 1 << (m & 0x0f); > int i; > char ch; > ssize_t count = 0; > > - if (*ppos >= ARRAY_SIZE(rm)) > + if (*ppos < 0 || *ppos >= ARRAY_SIZE(rm)) > return 0; > > for (i = *ppos; (i < (*ppos + len)) && (i < ARRAY_SIZE(rm)); > i++) { > ch = (inl(base + rm[i].rd_offset) & rd_bit) ? > rm[i].on : rm[i].off; > > if (put_user(ch, buf+count)) > return -EFAULT; > > count++; > > -- > Greetings, Michael. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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