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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <1564511696-4044-1-git-send-email-jrdr.linux@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9334 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1907300202 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9334 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1907300202 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 7/30/19 2:34 PM, Souptick Joarder wrote: > 'commit df9bde015a72 ("xen/gntdev.c: convert to use vm_map_pages()")' > breaks gntdev driver. If vma->vm_pgoff > 0, vm_map_pages() > will: > - use map->pages starting at vma->vm_pgoff instead of 0 > - verify map->count against vma_pages()+vma->vm_pgoff instead of just > vma_pages(). > > In practice, this breaks using a single gntdev FD for mapping multiple > grants. > > relevant strace output: > [pid 857] ioctl(7, IOCTL_GNTDEV_MAP_GRANT_REF, 0x7ffd3407b6d0) = 0 > [pid 857] mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_SHARED, 7, 0) = > 0x777f1211b000 > [pid 857] ioctl(7, IOCTL_GNTDEV_SET_UNMAP_NOTIFY, 0x7ffd3407b710) = 0 > [pid 857] ioctl(7, IOCTL_GNTDEV_MAP_GRANT_REF, 0x7ffd3407b6d0) = 0 > [pid 857] mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_SHARED, 7, > 0x1000) = -1 ENXIO (No such device or address) > > details here: > https://github.com/QubesOS/qubes-issues/issues/5199 > > The reason is -> ( copying Marek's word from discussion) > > vma->vm_pgoff is used as index passed to gntdev_find_map_index. It's > basically using this parameter for "which grant reference to map". > map struct returned by gntdev_find_map_index() describes just the pages > to be mapped. Specifically map->pages[0] should be mapped at > vma->vm_start, not vma->vm_start+vma->vm_pgoff*PAGE_SIZE. > > When trying to map grant with index (aka vma->vm_pgoff) > 1, > __vm_map_pages() will refuse to map it because it will expect map->count > to be at least vma_pages(vma)+vma->vm_pgoff, while it is exactly > vma_pages(vma). > > Converting vm_map_pages() to use vm_map_pages_zero() will fix the > problem. > > Marek has tested and confirmed the same. Cc: stable@vger.kernel.org # v5.2+ Fixes: df9bde015a72 ("xen/gntdev.c: convert to use vm_map_pages()") > Reported-by: Marek Marczykowski-Górecki > Signed-off-by: Souptick Joarder > Tested-by: Marek Marczykowski-Górecki Reviewed-by: Boris Ostrovsky > --- > drivers/xen/gntdev.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c > index 4c339c7..a446a72 100644 > --- a/drivers/xen/gntdev.c > +++ b/drivers/xen/gntdev.c > @@ -1143,7 +1143,7 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma) > goto out_put_map; > > if (!use_ptemod) { > - err = vm_map_pages(vma, map->pages, map->count); > + err = vm_map_pages_zero(vma, map->pages, map->count); > if (err) > goto out_put_map; > } else {