Hi, Any comment on this last version? Any chance to be merged? Thanks, Laurent Le 10/10/2018 à 18:14, Laurent Vivier a écrit : > v6: Return &init_binfmt_ns instead of NULL in binfmt_ns() > This should never happen, but to stay safe return a > value we can use. > change subject from "RFC" to "PATCH" > > v5: Use READ_ONCE()/WRITE_ONCE() > move mount pointer struct init to bm_fill_super() and add smp_wmb() > remove useless NULL value init > add WARN_ON_ONCE() > > v4: first user namespace is initialized with &init_binfmt_ns, > all new user namespaces are initialized with a NULL and use > the one of the first parent that is not NULL. The pointer > is initialized to a valid value the first time the binfmt_misc > fs is mounted in the current user namespace. > This allows to not change the way it was working before: > new ns inherits values from its parent, and if parent value is modified > (or parent creates its own binfmt entry by mounting the fs) child > inherits it (unless it has itself mounted the fs). > > v3: create a structure to store binfmt_misc data, > add a pointer to this structure in the user_namespace structure, > in init_user_ns structure this pointer points to an init_binfmt_ns > structure. And all new user namespaces point to this init structure. > A new binfmt namespace structure is allocated if the binfmt_misc > filesystem is mounted in a user namespace that is not the initial > one but its binfmt namespace pointer points to the initial one. > add override_creds()/revert_creds() around open_exec() in > bm_register_write() > > v2: no new namespace, binfmt_misc data are now part of > the mount namespace > I put this in mount namespace instead of user namespace > because the mount namespace is already needed and > I don't want to force to have the user namespace for that. > As this is a filesystem, it seems logic to have it here. > > This allows to define a new interpreter for each new container. > > But the main goal is to be able to chroot to a directory > using a binfmt_misc interpreter without being root. > > I have a modified version of unshare at: > > git@xxxxxxxxxx:vivier/util-linux.git branch unshare-chroot > > with some new options to unshare binfmt_misc namespace and to chroot > to a directory. > > If you have a directory /chroot/powerpc/jessie containing debian for powerpc > binaries and a qemu-ppc interpreter, you can do for instance: > > $ uname -a > Linux fedora28-wor-2 4.19.0-rc5+ #18 SMP Mon Oct 1 00:32:34 CEST 2018 x86_64 x86_64 x86_64 GNU/Linux > $ ./unshare --map-root-user --fork --pid \ > --load-interp ":qemu-ppc:M::\x7fELF\x01\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x14:\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff:/qemu-ppc:OC" \ > --root=/chroot/powerpc/jessie /bin/bash -l > # uname -a > Linux fedora28-wor-2 4.19.0-rc5+ #18 SMP Mon Oct 1 00:32:34 CEST 2018 ppc GNU/Linux > # id > uid=0(root) gid=0(root) groups=0(root),65534(nogroup) > # ls -l > total 5940 > drwxr-xr-x. 2 nobody nogroup 4096 Aug 12 00:58 bin > drwxr-xr-x. 2 nobody nogroup 4096 Jun 17 20:26 boot > drwxr-xr-x. 4 nobody nogroup 4096 Aug 12 00:08 dev > drwxr-xr-x. 42 nobody nogroup 4096 Sep 28 07:25 etc > drwxr-xr-x. 3 nobody nogroup 4096 Sep 28 07:25 home > drwxr-xr-x. 9 nobody nogroup 4096 Aug 12 00:58 lib > drwxr-xr-x. 2 nobody nogroup 4096 Aug 12 00:08 media > drwxr-xr-x. 2 nobody nogroup 4096 Aug 12 00:08 mnt > drwxr-xr-x. 3 nobody nogroup 4096 Aug 12 13:09 opt > dr-xr-xr-x. 143 nobody nogroup 0 Sep 30 23:02 proc > -rwxr-xr-x. 1 nobody nogroup 6009712 Sep 28 07:22 qemu-ppc > drwx------. 3 nobody nogroup 4096 Aug 12 12:54 root > drwxr-xr-x. 3 nobody nogroup 4096 Aug 12 00:08 run > drwxr-xr-x. 2 nobody nogroup 4096 Aug 12 00:58 sbin > drwxr-xr-x. 2 nobody nogroup 4096 Aug 12 00:08 srv > drwxr-xr-x. 2 nobody nogroup 4096 Apr 6 2015 sys > drwxrwxrwt. 2 nobody nogroup 4096 Sep 28 10:31 tmp > drwxr-xr-x. 10 nobody nogroup 4096 Aug 12 00:08 usr > drwxr-xr-x. 11 nobody nogroup 4096 Aug 12 00:08 var > > If you want to use the qemu binary provided by your distro, you can use > > --load-interp ":qemu-ppc:M::\x7fELF\x01\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x14:\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff:/bin/qemu-ppc-static:OCF" > > With the 'F' flag, qemu-ppc-static will be then loaded from the main root > filesystem before switching to the chroot. > > Laurent Vivier (1): > ns: add binfmt_misc to the user namespace > > fs/binfmt_misc.c | 111 ++++++++++++++++++++++++--------- > include/linux/user_namespace.h | 15 +++++ > kernel/user.c | 14 +++++ > kernel/user_namespace.c | 3 + > 4 files changed, 115 insertions(+), 28 deletions(-) >
