Messages in this thread | | | Date | Sun, 27 Jul 2014 19:44:08 +0100 | From | Malcolm Priestley <> | Subject | Re: [PATCH] staging: vt6655: fix direct dereferencing of user pointer |
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On 27/07/14 19:21, Greg Kroah-Hartman wrote: > On Sat, Jul 26, 2014 at 11:44:57AM +0100, Malcolm Priestley wrote: >> On 26/07/14 10:18, Guillaume CLÉMENT wrote: >>> On Sat, Jul 26, 2014 at 10:24:30AM +0200, Guillaume CLÉMENT wrote: >>>> Hi Malcolm, >>>> >>>> On Sat, Jul 26, 2014 at 12:09:49AM +0100, Malcolm Priestley wrote: >>>>> Hi Guillaume >>>>> >>>>> On 25/07/14 13:47, Guillaume Clement wrote: >>>>>> Sparse reported that the data from tagSCmdRequest is given by >>>>>> userspace, so it should be tagged as such. >>>>> extra is not in user space >>>>> >>>> >>>> All right. >>>> >>>> This is still confusing to me because, taking the SIOCSIWGENIE ioctl as >>>> an example, in device_main.c, we have this code: >>>> >>>> rc = iwctl_siwgenie(dev, NULL, &(wrq->u.data), wrq->u.data.pointer); >>>> >>>> Here the extra parameter is the last one, wrq->u.data.pointer. >>>> >>>> I was led to believe that wrq->u.data.pointer is in userspace (this was >>>> reported by sparse actually) because the pointer field in data is >>>> actually defined as __user. >>>> >>>> >>> By the way, the original code (before my patch) reads: >>> >>> if ((wrq->length < 2) || (extra[1]+2 != wrq->length)) { >>> ret = -EINVAL; >>> goto out; >>> } >>> if (wrq->length > MAX_WPA_IE_LEN) { >>> ret = -ENOMEM; >>> goto out; >>> } >>> memset(pMgmt->abyWPAIE, 0, MAX_WPA_IE_LEN); >>> if (copy_from_user(pMgmt->abyWPAIE, extra, wrq->length)) { >>> ret = -EFAULT; >>> goto out; >>> } >>> >>> Note extra[1] and later copy_from_user(x, extra, y). >>> >>> If extra is not in userspace, we should not call copy_from_user, and if >>> it is, we should not dereference it. There is definitely something fishy >>> here. >>> >> >> I got it wrong when the iw_handler is not present a standard ioctl is called >> extra is in userspace. >> >> Sorry for the noise. > > So this patch is acceptable? > Yes, this patch is okay.
> confused, > > greg k-h >
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