Messages in this thread | | | Date | Sat, 26 Jul 2014 11:18:45 +0200 | From | Guillaume CLÉMENT <> | Subject | Re: [PATCH] staging: vt6655: fix direct dereferencing of user pointer |
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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. -- 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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