bpf: Fix use-after-free in bpf_uprobe_multi_link_attach()

commit 5fe6e308abaea082c20fbf2aa5df8e14495622cf upstream.

If bpf_link_prime() fails, bpf_uprobe_multi_link_attach() goes to the
error_free label and frees the array of bpf_uprobe's without calling
bpf_uprobe_unregister().

This leaks bpf_uprobe->uprobe and worse, this frees bpf_uprobe->consumer
without removing it from the uprobe->consumers list.

Fixes: 89ae89f53d20 ("bpf: Add multi uprobe link")
Closes: https://lore.kernel.org/all/000000000000382d39061f59f2dd@google.com/
Reported-by: syzbot+f7a1c2c2711e4a780f19@syzkaller.appspotmail.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: syzbot+f7a1c2c2711e4a780f19@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240813152524.GA7292@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index f0b7e9eb8172985c73eb43d434292bf08ba07858..433be6bc8b778605223161f38348145e6710f77d 100644 (file)
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -3484,17 +3484,20 @@ int bpf_uprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
                                             uprobes[i].ref_ctr_offset,
                                             &uprobes[i].consumer);
                if (err) {
-                       bpf_uprobe_unregister(&path, uprobes, i);
-                       goto error_free;
+                       link->cnt = i;
+                       goto error_unregister;
                }
        }
 
        err = bpf_link_prime(&link->link, &link_primer);
        if (err)
-               goto error_free;
+               goto error_unregister;
 
        return bpf_link_settle(&link_primer);
 
+error_unregister:
+       bpf_uprobe_unregister(&path, uprobes, link->cnt);
+
 error_free:
        kvfree(uprobes);
        kfree(link);