tracing: Fix syscall tracepoint use-after-free

The grace period used internally within tracepoint.c:release_probes()
uses call_rcu() to batch waiting for quiescence of old probe arrays,
rather than using the tracepoint_synchronize_unregister() which blocks
while waiting for quiescence.

With the introduction of faultable syscall tracepoints, this causes
use-after-free issues reproduced with syzkaller.

Fix this by using the appropriate call_rcu() or call_rcu_tasks_trace()
before invoking the rcu_free_old_probes callback. This can be chosen
using the tracepoint_is_faultable() API.

A similar issue exists in bpf use of call_rcu(). Fixing this is left to
a separate change.

Reported-by: syzbot+b390c8062d8387b6272a@syzkaller.appspotmail.com
Fixes: a363d27cdbc2 ("tracing: Allow system call tracepoints to handle page faults")
Tested-by: Jordan Rife <jrife@google.com>
Cc: Michael Jeanson <mjeanson@efficios.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Yonghong Song <yhs@fb.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: bpf@vger.kernel.org
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Jordan Rife <jrife@google.com>
Cc: linux-trace-kernel@vger.kernel.org
Link: https://lore.kernel.org/20241031152056.744137-4-mathieu.desnoyers@efficios.com
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 5658dc9..1848ce7 100644 (file)
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -106,13 +106,16 @@ static void rcu_free_old_probes(struct rcu_head *head)
        kfree(container_of(head, struct tp_probes, rcu));
 }
 
-static inline void release_probes(struct tracepoint_func *old)
+static inline void release_probes(struct tracepoint *tp, struct tracepoint_func *old)
 {
        if (old) {
                struct tp_probes *tp_probes = container_of(old,
                        struct tp_probes, probes[0]);
 
-               call_rcu(&tp_probes->rcu, rcu_free_old_probes);
+               if (tracepoint_is_faultable(tp))
+                       call_rcu_tasks_trace(&tp_probes->rcu, rcu_free_old_probes);
+               else
+                       call_rcu(&tp_probes->rcu, rcu_free_old_probes);
        }
 }
 
@@ -334,7 +337,7 @@ static int tracepoint_add_func(struct tracepoint *tp,
                break;
        }
 
-       release_probes(old);
+       release_probes(tp, old);
        return 0;
 }
 
@@ -405,7 +408,7 @@ static int tracepoint_remove_func(struct tracepoint *tp,
                WARN_ON_ONCE(1);
                break;
        }
-       release_probes(old);
+       release_probes(tp, old);
        return 0;
 }