On Mon, Dec 05, 2016 at 04:17:53PM +0100, Johannes Thumshirn wrote: > 633 hp = &srp->header; > [...] > 646 hp->dxferp = (char __user *)buf + cmd_size; > So the memory for hp->dxferp comes from: > 633 hp = &srp->header; ???? > >From my debug instrumentation I see that the dxferp ends up in the > iovec_iter's kvec->iov_base and the faulting address is always dxferp + n * > 4k with n in [1, 16] (and we're copying 16 4k pages from the iovec into the > bio). _Address_ of hp->dxferp comes from that assignment; the value is 'buf' argument of sg_write() + small offset. In this case, it should point inside a pipe buffer, which is, indeed, at a kernel address. Who'd allocated srp is irrelevant. And if you end up dereferencing more than one page worth there, you do have a problem - pipe buffers are not going to be that large. Could you slap WARN_ON((size_t)input_size > count); right after the calculation of input_size in sg_write() and see if it triggers on your reproducer? -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
