From 00244bdaa423d93f4571f3f6854378ce3365e524 Mon Sep 17 00:00:00 2001 From: Leon Hwang Date: Wed, 5 Aug 2026 23:08:09 +0800 Subject: [PATCH] bpf: Fix sleepable check for tracing/lsm prog When CONFIG_FUNCTION_ERROR_INJECTION is disabled, a sleepable tracing prog is allowed to attach to '__x64_'-alike prefix symbols. It is because the verifier does not verify whether the symbol is a kernel function or a bpf prog. That said, a sleepable tracing prog is allowed to attach to a bpf prog target whose name has '__x64_'-alike prefix. For example, a sleepable fentry prog attaches to a '__x64_sys_nop' XDP prog, and copies buffer from a user pointer with bpf_copy_from_user() helper. After attaching the XDP prog to lo interface, the kernel BUG could be triggered by 'ping -c 1 -W 1 127.0.0.1': [ 3.460756] BUG: sleeping function called from invalid context at kernel/bpf/trampoline.c:1324 Fix it by disallowing sleepable prog always when its target btf is not a kernel's btf. Fixes: 16d9c5660692 ("bpf: Always allow sleepable programs on syscalls") Signed-off-by: Leon Hwang Signed-off-by: Andrii Nakryiko Acked-by: Viktor Malik Link: https://lore.kernel.org/bpf/20260805150810.34907-2-leon.hwang@linux.dev --- kernel/bpf/verifier.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 4db151e24355..d925197c2e5f 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -19022,6 +19022,9 @@ static int btf_id_allow_sleepable(u32 btf_id, unsigned long addr, const struct b const struct btf_type *t; const char *tname; + if (!btf_is_kernel(btf)) + return -EINVAL; + switch (prog->type) { case BPF_PROG_TYPE_TRACING: t = btf_type_by_id(btf, btf_id);