6.12-stable review patch. If anyone has any objections, please let me know.
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From: Andrea Righi arighi@nvidia.com
[ Upstream commit 23579010cf0a12476e96a5f1acdf78a9c5843657 ]
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 arighi@nvidia.com Signed-off-by: Andrii Nakryiko andrii@kernel.org Link: https://lore.kernel.org/bpf/20241217195813.622568-1-arighi@nvidia.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/verifier.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 4c486a0bfcc4..84d958f2c031 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -21085,11 +21085,15 @@ static int do_misc_fixups(struct bpf_verifier_env *env) * 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;