Cc'ing Igor & Xiao. On 7/8/19 11:19 PM, Julio Montes wrote: > Currently is not possible to use a file that is part of a read-only > filesystem as memory backend for nvdimm devices, even if this is not modified > in the guest. In order to improve the security of Virtual Machines that share > and do not modify the memory-backend-file, QEMU should support > read-only memory-backeds. > > Use case: > * Kata Containers use a memory-backed-file as read-only rootfs, and this > file is used to start all the virtual machines in the node. > It would be really bad if somehow a malicious container modified it. > > Signed-off-by: Julio Montes <julio.mon...@intel.com> > --- > exec.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/exec.c b/exec.c > index 50ea9c5aaa..1eb170b55a 100644 > --- a/exec.c > +++ b/exec.c > @@ -1852,6 +1852,12 @@ static int file_ram_open(const char *path, > break; > } > g_free(filename); > + } else if (errno == EROFS) { > + fd = open(path, O_RDONLY);
While I can understand your use case, I'm not sure we want this silenced as default. I'd expect an explicit command line option for that backend, but I don't know well this area so let's wait for other to review. > + if (fd >= 0) { > + /* @path names an existing read-only file, use it */ > + break; > + } > } > if (errno != EEXIST && errno != EINTR) { > error_setg_errno(errp, errno, > -- > 2.17.2 >