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authorAlexei Starovoitov <ast@fb.com>2016-04-06 18:43:28 -0700
committerDavid S. Miller <davem@davemloft.net>2016-04-07 21:04:26 -0400
commit32bbe0078afe86a8bf4c67c6b3477781b15e94dc (patch)
tree8c5290f51108de3a2c98cb7171942fb9d5e36ab2 /kernel
parent9940d67c93b5bb7ddcf862b41b1847cb728186c4 (diff)
downloadlinux-stericsson-32bbe0078afe86a8bf4c67c6b3477781b15e94dc.tar.gz
bpf: sanitize bpf tracepoint access
during bpf program loading remember the last byte of ctx access and at the time of attaching the program to tracepoint check that the program doesn't access bytes beyond defined in tracepoint fields This also disallows access to __dynamic_array fields, but can be relaxed in the future. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/verifier.c6
-rw-r--r--kernel/events/core.c8
-rw-r--r--kernel/trace/trace_events.c18
3 files changed, 31 insertions, 1 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 2e08f8e9b771..58792fed5678 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -652,8 +652,12 @@ static int check_ctx_access(struct verifier_env *env, int off, int size,
enum bpf_access_type t)
{
if (env->prog->aux->ops->is_valid_access &&
- env->prog->aux->ops->is_valid_access(off, size, t))
+ env->prog->aux->ops->is_valid_access(off, size, t)) {
+ /* remember the offset of last byte accessed in ctx */
+ if (env->prog->aux->max_ctx_offset < off + size)
+ env->prog->aux->max_ctx_offset = off + size;
return 0;
+ }
verbose("invalid bpf_context access off=%d size=%d\n", off, size);
return -EACCES;
diff --git a/kernel/events/core.c b/kernel/events/core.c
index e5ffe97d6166..9a01019ff7c8 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7133,6 +7133,14 @@ static int perf_event_set_bpf_prog(struct perf_event *event, u32 prog_fd)
return -EINVAL;
}
+ if (is_tracepoint) {
+ int off = trace_event_get_offsets(event->tp_event);
+
+ if (prog->aux->max_ctx_offset > off) {
+ bpf_prog_put(prog);
+ return -EACCES;
+ }
+ }
event->tp_event->prog = prog;
return 0;
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 05ddc0820771..ced963049e0a 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -204,6 +204,24 @@ static void trace_destroy_fields(struct trace_event_call *call)
}
}
+/*
+ * run-time version of trace_event_get_offsets_<call>() that returns the last
+ * accessible offset of trace fields excluding __dynamic_array bytes
+ */
+int trace_event_get_offsets(struct trace_event_call *call)
+{
+ struct ftrace_event_field *tail;
+ struct list_head *head;
+
+ head = trace_get_fields(call);
+ /*
+ * head->next points to the last field with the largest offset,
+ * since it was added last by trace_define_field()
+ */
+ tail = list_first_entry(head, struct ftrace_event_field, link);
+ return tail->offset + tail->size;
+}
+
int trace_event_raw_init(struct trace_event_call *call)
{
int id;