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authorTycho Andersen <tycho.andersen@canonical.com>2015-10-27 09:23:59 +0900
committerDavid S. Miller <davem@davemloft.net>2015-10-27 19:55:13 -0700
commitf8e529ed941ba2bbcbf310b575d968159ce7e895 (patch)
tree2acad2e0218452811ec419929aad3647ad0c75d0 /kernel
parent5b9e3bd5b2f807f66a959cc079c495915f032c67 (diff)
seccomp, ptrace: add support for dumping seccomp filters
This patch adds support for dumping a process' (classic BPF) seccomp filters via ptrace. PTRACE_SECCOMP_GET_FILTER allows the tracer to dump the user's classic BPF seccomp filters. addr should be an integer which represents the ith seccomp filter (0 is the most recently installed filter). data should be a struct sock_filter * with enough room for the ith filter, or NULL, in which case the filter is not saved. The return value for this command is the number of BPF instructions the program represents, or negative in the case of errors. Command specific errors are ENOENT: which indicates that there is no ith filter in this seccomp tree, and EMEDIUMTYPE, which indicates that the ith filter was not installed as a classic BPF filter. A caveat with this approach is that there is no way to get explicitly at the heirarchy of seccomp filters, and users need to memcmp() filters to decide which are inherited. This means that a task which installs two of the same filter can potentially confuse users of this interface. v2: * make save_orig const * check that the orig_prog exists (not necessary right now, but when grows eBPF support it will be) * s/n/filter_off and make it an unsigned long to match ptrace * count "down" the tree instead of "up" when passing a filter offset v3: * don't take the current task's lock for inspecting its seccomp mode * use a 0x42** constant for the ptrace command value v4: * don't copy to userspace while holding spinlocks v5: * add another condition to WARN_ON v6: * rebase on net-next Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com> Acked-by: Kees Cook <keescook@chromium.org> CC: Will Drewry <wad@chromium.org> Reviewed-by: Oleg Nesterov <oleg@redhat.com> CC: Andy Lutomirski <luto@amacapital.net> CC: Pavel Emelyanov <xemul@parallels.com> CC: Serge E. Hallyn <serge.hallyn@ubuntu.com> CC: Alexei Starovoitov <ast@kernel.org> CC: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/ptrace.c5
-rw-r--r--kernel/seccomp.c76
2 files changed, 80 insertions, 1 deletions
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 787320de68e0..b760bae64cf1 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -1016,6 +1016,11 @@ int ptrace_request(struct task_struct *child, long request,
break;
}
#endif
+
+ case PTRACE_SECCOMP_GET_FILTER:
+ ret = seccomp_get_filter(child, addr, datavp);
+ break;
+
default:
break;
}
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 06858a74bb9c..580ac2d4024f 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -347,6 +347,7 @@ static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
{
struct seccomp_filter *sfilter;
int ret;
+ const bool save_orig = config_enabled(CONFIG_CHECKPOINT_RESTORE);
if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
return ERR_PTR(-EINVAL);
@@ -370,7 +371,7 @@ static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
return ERR_PTR(-ENOMEM);
ret = bpf_prog_create_from_user(&sfilter->prog, fprog,
- seccomp_check_filter, false);
+ seccomp_check_filter, save_orig);
if (ret < 0) {
kfree(sfilter);
return ERR_PTR(ret);
@@ -867,3 +868,76 @@ long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter)
/* prctl interface doesn't have flags, so they are always zero. */
return do_seccomp(op, 0, uargs);
}
+
+#if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE)
+long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
+ void __user *data)
+{
+ struct seccomp_filter *filter;
+ struct sock_fprog_kern *fprog;
+ long ret;
+ unsigned long count = 0;
+
+ if (!capable(CAP_SYS_ADMIN) ||
+ current->seccomp.mode != SECCOMP_MODE_DISABLED) {
+ return -EACCES;
+ }
+
+ spin_lock_irq(&task->sighand->siglock);
+ if (task->seccomp.mode != SECCOMP_MODE_FILTER) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ filter = task->seccomp.filter;
+ while (filter) {
+ filter = filter->prev;
+ count++;
+ }
+
+ if (filter_off >= count) {
+ ret = -ENOENT;
+ goto out;
+ }
+ count -= filter_off;
+
+ filter = task->seccomp.filter;
+ while (filter && count > 1) {
+ filter = filter->prev;
+ count--;
+ }
+
+ if (WARN_ON(count != 1 || !filter)) {
+ /* The filter tree shouldn't shrink while we're using it. */
+ ret = -ENOENT;
+ goto out;
+ }
+
+ fprog = filter->prog->orig_prog;
+ if (!fprog) {
+ /* This must be a new non-cBPF filter, since we save every
+ * every cBPF filter's orig_prog above when
+ * CONFIG_CHECKPOINT_RESTORE is enabled.
+ */
+ ret = -EMEDIUMTYPE;
+ goto out;
+ }
+
+ ret = fprog->len;
+ if (!data)
+ goto out;
+
+ get_seccomp_filter(task);
+ spin_unlock_irq(&task->sighand->siglock);
+
+ if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog)))
+ ret = -EFAULT;
+
+ put_seccomp_filter(task);
+ return ret;
+
+out:
+ spin_unlock_irq(&task->sighand->siglock);
+ return ret;
+}
+#endif