From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 08638178372 for ; Fri, 21 Nov 2025 15:20:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763738404; cv=none; b=Buf90bV6oaRQLtfcnBFAdC0zUDiWwfw7x0RY89NV6Tav4vMEVaR8nTFHcZEzGfwfSa3Em8ztvRQdFE0KRYhWI4Yx3E4hkdU3P5RxMdZbhv3LarabaDRS/xXYVF51KTjgGFYtN3vX/zWJWMjZ2teulhojtObW62RNygKZAmhhV9Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763738404; c=relaxed/simple; bh=S91R0JrQrKJKxdEYRIXhRczEsMtoKEtP1XH3tqkO6NQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=eVDoG+cslIbd9A7fwb92oKJNa2ulQDtpfS6mcjyppcVEfNc8UYNYgPn5VbKWiOZF0K3KXTRH+C8XRRBBSAqHTmbTDxsaEN9TqrlMQ8NPZsBVcd8v6Cwh2/LzA+HjDiwNSzTcLS6bFMQq3NQcobA8da7z8r/+kzCCo0PsoaEFoI0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=idHHdSW+; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="idHHdSW+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9632BC4CEF1; Fri, 21 Nov 2025 15:20:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763738403; bh=S91R0JrQrKJKxdEYRIXhRczEsMtoKEtP1XH3tqkO6NQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=idHHdSW+y/gTsOGUlykky0m6rMzwS5RWJpnd/xjRFJ3NSWgswRIFhMg6de1DKk6P2 q06LoWEJobYBtr4WkU0js7fcd8B8RowDUxZ7RuNCKQ/QimbOi7+TZAx6oZ/gYPIuOe 8dAdUJVLhx0RQIBFw6ly2Wr+UX40u0QkxbzJ+fySVijSD4fPbPOXQz9DEnnbI+qLgK rkm4u/mQvck/+8H7bcsFGvVvf/oIHOcbEQTl+RVaxoCbddD5gyTb7y13+qE7fyOYaP NNxj3zo+Ackiyd3Dp8rBUb9p36iSHE59Gv67JTUYQ7gDp6PFQK5AZs/4odDtwRPb1v GX+CV3Qzi/BqA== From: Sasha Levin To: stable@vger.kernel.org Cc: Song Liu , Andrey Grodzovsky , "Steven Rostedt (Google)" , "Masami Hiramatsu (Google)" , Jiri Olsa , Alexei Starovoitov , Sasha Levin Subject: [PATCH 6.6.y] ftrace: Fix BPF fexit with livepatch Date: Fri, 21 Nov 2025 10:20:00 -0500 Message-ID: <20251121152000.2567643-1-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <2025112016-arrogance-recast-439f@gregkh> References: <2025112016-arrogance-recast-439f@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Song Liu [ Upstream commit 56b3c85e153b84f27e6cff39623ba40a1ad299d3 ] When livepatch is attached to the same function as bpf trampoline with a fexit program, bpf trampoline code calls register_ftrace_direct() twice. The first time will fail with -EAGAIN, and the second time it will succeed. This requires register_ftrace_direct() to unregister the address on the first attempt. Otherwise, the bpf trampoline cannot attach. Here is an easy way to reproduce this issue: insmod samples/livepatch/livepatch-sample.ko bpftrace -e 'fexit:cmdline_proc_show {}' ERROR: Unable to attach probe: fexit:vmlinux:cmdline_proc_show... Fix this by cleaning up the hash when register_ftrace_function_nolock hits errors. Also, move the code that resets ops->func and ops->trampoline to the error path of register_ftrace_direct(); and add a helper function reset_direct() in register_ftrace_direct() and unregister_ftrace_direct(). Fixes: d05cb470663a ("ftrace: Fix modification of direct_function hash while in use") Cc: stable@vger.kernel.org # v6.6+ Reported-by: Andrey Grodzovsky Closes: https://lore.kernel.org/live-patching/c5058315a39d4615b333e485893345be@crowdstrike.com/ Cc: Steven Rostedt (Google) Cc: Masami Hiramatsu (Google) Acked-and-tested-by: Andrey Grodzovsky Signed-off-by: Song Liu Reviewed-by: Jiri Olsa Link: https://lore.kernel.org/r/20251027175023.1521602-2-song@kernel.org Signed-off-by: Alexei Starovoitov Acked-by: Steven Rostedt (Google) [ moved cleanup to reset_direct() ] Signed-off-by: Sasha Levin --- kernel/bpf/trampoline.c | 4 ---- kernel/trace/ftrace.c | 20 ++++++++++++++------ 2 files changed, 14 insertions(+), 10 deletions(-) diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c index e97aeda3a86b5..b6024fc903490 100644 --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -460,10 +460,6 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mut * BPF_TRAMP_F_SHARE_IPMODIFY is set, we can generate the * trampoline again, and retry register. */ - /* reset fops->func and fops->trampoline for re-register */ - tr->fops->func = NULL; - tr->fops->trampoline = 0; - /* reset im->image memory attr for arch_prepare_bpf_trampoline */ set_memory_nx((long)im->image, 1); set_memory_rw((long)im->image, 1); diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 15785a729a0cd..ecda59d6acb4c 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -5370,6 +5370,17 @@ static void remove_direct_functions_hash(struct ftrace_hash *hash, unsigned long } } +static void reset_direct(struct ftrace_ops *ops, unsigned long addr) +{ + struct ftrace_hash *hash = ops->func_hash->filter_hash; + + remove_direct_functions_hash(hash, addr); + + /* cleanup for possible another register call */ + ops->func = NULL; + ops->trampoline = 0; +} + /** * register_ftrace_direct - Call a custom trampoline directly * for multiple functions registered in @ops @@ -5465,6 +5476,8 @@ int register_ftrace_direct(struct ftrace_ops *ops, unsigned long addr) ops->direct_call = addr; err = register_ftrace_function_nolock(ops); + if (err) + reset_direct(ops, addr); out_unlock: mutex_unlock(&direct_mutex); @@ -5497,7 +5510,6 @@ EXPORT_SYMBOL_GPL(register_ftrace_direct); int unregister_ftrace_direct(struct ftrace_ops *ops, unsigned long addr, bool free_filters) { - struct ftrace_hash *hash = ops->func_hash->filter_hash; int err; if (check_direct_multi(ops)) @@ -5507,13 +5519,9 @@ int unregister_ftrace_direct(struct ftrace_ops *ops, unsigned long addr, mutex_lock(&direct_mutex); err = unregister_ftrace_function(ops); - remove_direct_functions_hash(hash, addr); + reset_direct(ops, addr); mutex_unlock(&direct_mutex); - /* cleanup for possible another register call */ - ops->func = NULL; - ops->trampoline = 0; - if (free_filters) ftrace_free_filter(ops); return err; -- 2.51.0