tracing/trigger: Fix to return error if failed to alloc snapshot

stable inclusion
from stable-v4.19.307
commit bcf4a115a5068f3331fafb8c176c1af0da3d8b19
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9HL6U
CVE: CVE-2024-26920

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bcf4a115a5068f3331fafb8c176c1af0da3d8b19

--------------------------------

commit 0958b33ef5a04ed91f61cef4760ac412080c4e08 upstream.

Fix register_snapshot_trigger() to return error code if it failed to
allocate a snapshot instead of 0 (success). Unless that, it will register
snapshot trigger without an error.

Link: https://lore.kernel.org/linux-trace-kernel/170622977792.270660.2789298642759362200.stgit@devnote2



Fixes: 0bbe7f71 ("tracing: Fix the race between registering 'snapshot' event trigger and triggering 'snapshot' operation")
Cc: stable@vger.kernel.org
Cc: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>