This includes the thread group leader ID in the seccomp_notif. This is immediately useful for opening up a pidfd for the group leader, as pidfds only work on group leaders.
Previously, it was considered to include an actual pidfd in the seccomp_notif structure[1], but it was suggested to avoid proliferating mechanisms to create pidfds[2]. [1]: https://lkml.org/lkml/2020/1/24/133 [2]: https://lkml.org/lkml/2020/5/15/481 Suggested-by: Christian Brauner <[email protected]> Signed-off-by: Sargun Dhillon <[email protected]> --- include/uapi/linux/seccomp.h | 2 + kernel/seccomp.c | 1 + tools/testing/selftests/seccomp/seccomp_bpf.c | 50 +++++++++++++++++++ 3 files changed, 53 insertions(+) diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h index c1735455bc53..f0c272ef0f1e 100644 --- a/include/uapi/linux/seccomp.h +++ b/include/uapi/linux/seccomp.h @@ -75,6 +75,8 @@ struct seccomp_notif { __u32 pid; __u32 flags; struct seccomp_data data; + __u32 tgid; + __u8 pad0[4]; }; /* diff --git a/kernel/seccomp.c b/kernel/seccomp.c index 55a6184f5990..538bcbbcf4da 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -1061,6 +1061,7 @@ static long seccomp_notify_recv(struct seccomp_filter *filter, unotif.id = knotif->id; unotif.pid = task_pid_vnr(knotif->task); + unotif.tgid = task_tgid_vnr(knotif->task); unotif.data = *(knotif->data); knotif->state = SECCOMP_NOTIFY_SENT; diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c index c0aa46ce14f6..5658c6e95461 100644 --- a/tools/testing/selftests/seccomp/seccomp_bpf.c +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c @@ -187,6 +187,8 @@ struct seccomp_notif { __u32 pid; __u32 flags; struct seccomp_data data; + __u32 tgid; + __u8 pad0[4]; }; struct seccomp_notif_resp { @@ -3226,6 +3228,8 @@ TEST(user_notification_basic) req.pid = 0; EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, &req), 0); } + EXPECT_EQ(pid, req.pid); + EXPECT_EQ(pid, req.tgid); pollfd.fd = listener; pollfd.events = POLLIN | POLLOUT; @@ -3453,6 +3457,7 @@ TEST(user_notification_child_pid_ns) EXPECT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, &req), 0); EXPECT_EQ(req.pid, pid); + EXPECT_EQ(req.tgid, pid); resp.id = req.id; resp.error = 0; @@ -3686,6 +3691,51 @@ TEST(user_notification_continue) } } +void *getppid_thread(void *arg) +{ + int *tid = arg; + + *tid = syscall(__NR_gettid); + if (*tid <= 0) + return (void *)(long)errno; + return NULL; +} + +TEST(user_notification_groupleader) +{ + struct seccomp_notif_resp resp = {}; + struct seccomp_notif req = {}; + int ret, listener, tid, pid; + pthread_t thread; + void *status; + + pid = getpid(); + ASSERT_GT(pid, 0); + + ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0); + ASSERT_EQ(0, ret) { + TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!"); + } + + listener = user_trap_syscall(__NR_gettid, + SECCOMP_FILTER_FLAG_NEW_LISTENER); + ASSERT_GE(listener, 0); + + ASSERT_EQ(0, pthread_create(&thread, NULL, getppid_thread, &tid)); + + ASSERT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, &req), 0); + resp.id = req.id; + resp.flags = SECCOMP_USER_NOTIF_FLAG_CONTINUE; + ASSERT_EQ(ioctl(listener, SECCOMP_IOCTL_NOTIF_SEND, &resp), 0); + + ASSERT_EQ(0, pthread_join(thread, &status)); + ASSERT_EQ(0, status); + + EXPECT_EQ(tid, req.pid); + EXPECT_EQ(pid, req.tgid); +} + + /* * TODO: * - add microbenchmarks -- 2.20.1
