From: Andrea Righi Date: Tue, 17 Dec 2024 19:58:13 +0000 (+0100) Subject: bpf: Fix bpf_get_smp_processor_id() on !CONFIG_SMP X-Git-Tag: v6.13-rc4~7^2~10 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=23579010cf0a12476e96a5f1acdf78a9c5843657;p=thirdparty%2Fkernel%2Flinux.git bpf: Fix bpf_get_smp_processor_id() on !CONFIG_SMP On x86-64 calling bpf_get_smp_processor_id() in a kernel with CONFIG_SMP disabled can trigger the following bug, as pcpu_hot is unavailable: [ 8.471774] BUG: unable to handle page fault for address: 00000000936a290c [ 8.471849] #PF: supervisor read access in kernel mode [ 8.471881] #PF: error_code(0x0000) - not-present page Fix by inlining a return 0 in the !CONFIG_SMP case. Fixes: 1ae6921009e5 ("bpf: inline bpf_get_smp_processor_id() helper") Signed-off-by: Andrea Righi Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20241217195813.622568-1-arighi@nvidia.com --- diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index f7f892a52a374..77f56674aaa99 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -21281,11 +21281,15 @@ patch_map_ops_generic: * changed in some incompatible and hard to support * way, it's fine to back out this inlining logic */ +#ifdef CONFIG_SMP insn_buf[0] = BPF_MOV32_IMM(BPF_REG_0, (u32)(unsigned long)&pcpu_hot.cpu_number); insn_buf[1] = BPF_MOV64_PERCPU_REG(BPF_REG_0, BPF_REG_0); insn_buf[2] = BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_0, 0); cnt = 3; - +#else + insn_buf[0] = BPF_ALU32_REG(BPF_XOR, BPF_REG_0, BPF_REG_0); + cnt = 1; +#endif new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt); if (!new_prog) return -ENOMEM;