Re: [PATCH v6 0/7] capabilities: Introduce CAP_CHECKPOINT_RESTORE

[Christian Brauner <christian.brauner@ubuntu.com>]

On Mon, Jul 20, 2020 at 02:46:37PM +0200, Adrian Reber wrote:
> On Mon, Jul 20, 2020 at 01:54:52PM +0200, Christian Brauner wrote:
> > On Sun, Jul 19, 2020 at 08:17:30PM +0200, Christian Brauner wrote:
> > > On Sun, Jul 19, 2020 at 12:04:10PM +0200, Adrian Reber wrote:
> > > > This is v6 of the 'Introduce CAP_CHECKPOINT_RESTORE' patchset. The
> > > > changes to v5 are:
> > > > 
> > > >  * split patch dealing with /proc/self/exe into two patches:
> > > >    * first patch to enable changing it with CAP_CHECKPOINT_RESTORE
> > > >      and detailed history in the commit message
> > > >    * second patch changes -EINVAL to -EPERM
> > > >  * use kselftest_harness.h infrastructure for test
> > > >  * replace if (!capable(CAP_SYS_ADMIN) || !capable(CAP_CHECKPOINT_RESTORE))
> > > >    with if (!checkpoint_restore_ns_capable(&init_user_ns))
> > > > 
> > > > Adrian Reber (5):
> > > >   capabilities: Introduce CAP_CHECKPOINT_RESTORE
> > > >   pid: use checkpoint_restore_ns_capable() for set_tid
> > > >   pid_namespace: use checkpoint_restore_ns_capable() for ns_last_pid
> > > >   proc: allow access in init userns for map_files with
> > > >     CAP_CHECKPOINT_RESTORE
> > > >   selftests: add clone3() CAP_CHECKPOINT_RESTORE test
> > > > 
> > > > Nicolas Viennot (2):
> > > >   prctl: Allow local CAP_CHECKPOINT_RESTORE to change /proc/self/exe
> > > >   prctl: exe link permission error changed from -EINVAL to -EPERM
> > > > 
> > > >  fs/proc/base.c                                |   8 +-
> > > >  include/linux/capability.h                    |   6 +
> > > >  include/uapi/linux/capability.h               |   9 +-
> > > >  kernel/pid.c                                  |   2 +-
> > > >  kernel/pid_namespace.c                        |   2 +-
> > > >  kernel/sys.c                                  |  13 +-
> > > >  security/selinux/include/classmap.h           |   5 +-
> > > >  tools/testing/selftests/clone3/.gitignore     |   1 +
> > > >  tools/testing/selftests/clone3/Makefile       |   4 +-
> > > >  .../clone3/clone3_cap_checkpoint_restore.c    | 177 ++++++++++++++++++
> > > >  10 files changed, 212 insertions(+), 15 deletions(-)
> > > >  create mode 100644 tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c
> > > > 
> > > > base-commit: d31958b30ea3b7b6e522d6bf449427748ad45822
> > > 
> > > Adrian, Nicolas thank you!
> > > I grabbed the series to run the various core test-suites we've added
> > > over the last year and pushed it to
> > > https://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux.git/log/?h=cap_checkpoint_restore
> > > for now to let kbuild/ltp chew on it for a bit.
> > 
> > Ok, I ran the test-suite this morning and there's nothing to worry about
> > it all passes _but_ the selftests had a bug using SKIP() instead of
> > XFAIL() and they mixed ksft_print_msg() and TH_LOG(). I know that I
> > think I mentioned to you that you can't use TH_LOG() outside of TEST*().
> > Turns out I was wrong. You can do it if you pass in a specific global
> > variable. Here's the diff I applied on top of the selftests you sent.
> > After these changes the output looks like this:
> > 
> > [==========] Running 1 tests from 1 test cases.
> > [ RUN      ] global.clone3_cap_checkpoint_restore
> > # clone3() syscall supported
> > clone3_cap_checkpoint_restore.c:155:clone3_cap_checkpoint_restore:Child has PID 12303
> > clone3_cap_checkpoint_restore.c:88:clone3_cap_checkpoint_restore:[12302] Trying clone3() with CLONE_SET_TID to 12303
> > clone3_cap_checkpoint_restore.c:55:clone3_cap_checkpoint_restore:Operation not permitted - Failed to create new process
> > clone3_cap_checkpoint_restore.c:90:clone3_cap_checkpoint_restore:[12302] clone3() with CLONE_SET_TID 12303 says:-1
> > clone3_cap_checkpoint_restore.c:88:clone3_cap_checkpoint_restore:[12302] Trying clone3() with CLONE_SET_TID to 12303
> > clone3_cap_checkpoint_restore.c:70:clone3_cap_checkpoint_restore:I am the parent (12302). My child's pid is 12303
> > clone3_cap_checkpoint_restore.c:63:clone3_cap_checkpoint_restore:I am the child, my PID is 12303 (expected 12303)
> > clone3_cap_checkpoint_restore.c:90:clone3_cap_checkpoint_restore:[12302] clone3() with CLONE_SET_TID 12303 says:0
> > [       OK ] global.clone3_cap_checkpoint_restore
> > [==========] 1 / 1 tests passed.
> > [  PASSED  ]
> > 
> > Ok with this below being applied on top of it?
> > 
> > diff --git a/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c b/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c
> > index c0d83511cd28..9562425aa0a9 100644
> > --- a/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c
> > +++ b/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c
> > @@ -38,7 +38,8 @@ static void child_exit(int ret)
> >  	_exit(ret);
> >  }
> >  
> > -static int call_clone3_set_tid(pid_t *set_tid, size_t set_tid_size)
> > +static int call_clone3_set_tid(struct __test_metadata *_metadata,
> > +			       pid_t *set_tid, size_t set_tid_size)
> >  {
> >  	int status;
> >  	pid_t pid = -1;
> > @@ -51,7 +52,7 @@ static int call_clone3_set_tid(pid_t *set_tid, size_t set_tid_size)
> >  
> >  	pid = sys_clone3(&args, sizeof(struct clone_args));
> >  	if (pid < 0) {
> > -		ksft_print_msg("%s - Failed to create new process\n", strerror(errno));
> > +		TH_LOG("%s - Failed to create new process", strerror(errno));
> >  		return -errno;
> >  	}
> >  
> > @@ -59,18 +60,17 @@ static int call_clone3_set_tid(pid_t *set_tid, size_t set_tid_size)
> >  		int ret;
> >  		char tmp = 0;
> >  
> > -		ksft_print_msg
> > -		    ("I am the child, my PID is %d (expected %d)\n", getpid(), set_tid[0]);
> > +		TH_LOG("I am the child, my PID is %d (expected %d)", getpid(), set_tid[0]);
> >  
> >  		if (set_tid[0] != getpid())
> >  			child_exit(EXIT_FAILURE);
> >  		child_exit(EXIT_SUCCESS);
> >  	}
> >  
> > -	ksft_print_msg("I am the parent (%d). My child's pid is %d\n", getpid(), pid);
> > +	TH_LOG("I am the parent (%d). My child's pid is %d", getpid(), pid);
> >  
> >  	if (waitpid(pid, &status, 0) < 0) {
> > -		ksft_print_msg("Child returned %s\n", strerror(errno));
> > +		TH_LOG("Child returned %s", strerror(errno));
> >  		return -errno;
> >  	}
> >  
> > @@ -80,13 +80,14 @@ static int call_clone3_set_tid(pid_t *set_tid, size_t set_tid_size)
> >  	return WEXITSTATUS(status);
> >  }
> >  
> > -static int test_clone3_set_tid(pid_t *set_tid, size_t set_tid_size)
> > +static int test_clone3_set_tid(struct __test_metadata *_metadata,
> > +			       pid_t *set_tid, size_t set_tid_size)
> >  {
> >  	int ret;
> >  
> > -	ksft_print_msg("[%d] Trying clone3() with CLONE_SET_TID to %d\n", getpid(), set_tid[0]);
> > -	ret = call_clone3_set_tid(set_tid, set_tid_size);
> > -	ksft_print_msg("[%d] clone3() with CLONE_SET_TID %d says:%d\n", getpid(), set_tid[0], ret);
> > +	TH_LOG("[%d] Trying clone3() with CLONE_SET_TID to %d", getpid(), set_tid[0]);
> > +	ret = call_clone3_set_tid(_metadata, set_tid, set_tid_size);
> > +	TH_LOG("[%d] clone3() with CLONE_SET_TID %d says:%d", getpid(), set_tid[0], ret);
> >  	return ret;
> >  }
> >  
> > @@ -144,7 +145,7 @@ TEST(clone3_cap_checkpoint_restore)
> >  	test_clone3_supported();
> >  
> >  	EXPECT_EQ(getuid(), 0)
> > -		SKIP(return, "Skipping all tests as non-root\n");
> > +		XFAIL(return, "Skipping all tests as non-root\n");
> >  
> >  	memset(&set_tid, 0, sizeof(set_tid));
> >  
> > @@ -162,16 +163,20 @@ TEST(clone3_cap_checkpoint_restore)
> >  
> >  	ASSERT_EQ(set_capability(), 0)
> >  		TH_LOG("Could not set CAP_CHECKPOINT_RESTORE");
> > -	prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0);
> > -	setgid(1000);
> > -	setuid(1000);
> > +
> > +	ASSERT_EQ(prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0), 0);
> > +
> > +	EXPECT_EQ(setgid(65534), 0)
> > +		TH_LOG("Failed to setgid(65534)");
> > +	ASSERT_EQ(setuid(65534), 0);
> > +
> >  	set_tid[0] = pid;
> >  	/* This would fail without CAP_CHECKPOINT_RESTORE */
> > -	ASSERT_EQ(test_clone3_set_tid(set_tid, 1), -EPERM);
> > +	ASSERT_EQ(test_clone3_set_tid(_metadata, set_tid, 1), -EPERM);
> >  	ASSERT_EQ(set_capability(), 0)
> >  		TH_LOG("Could not set CAP_CHECKPOINT_RESTORE");
> >  	/* This should work as we have CAP_CHECKPOINT_RESTORE as non-root */
> > -	ASSERT_EQ(test_clone3_set_tid(set_tid, 1), 0);
> > +	ASSERT_EQ(test_clone3_set_tid(_metadata, set_tid, 1), 0);
> >  }
> >  
> 
> Thanks for the changes. That looks much better.
> 
> Can you fix the test directly or do you need a new reworked patch from us?

No, I squashed this into your commit, added a comment about my changes,
signed it off and am going to push it out for some more testing.

Thanks!
Christian