From: Puranjay Mohan Date: Tue, 22 Jul 2025 13:34:09 +0000 (+0000) Subject: bpf, arm64: Fix fp initialization for exception boundary X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b114fcee766d5101eada1aca7bb5fd0a86c89b35;p=thirdparty%2Fkernel%2Fstable.git bpf, arm64: Fix fp initialization for exception boundary In the ARM64 BPF JIT when prog->aux->exception_boundary is set for a BPF program, find_used_callee_regs() is not called because for a program acting as exception boundary, all callee saved registers are saved. find_used_callee_regs() sets `ctx->fp_used = true;` when it sees FP being used in any of the instructions. For programs acting as exception boundary, ctx->fp_used remains false even if frame pointer is used by the program and therefore, FP is not set-up for such programs in the prologue. This can cause the kernel to crash due to a pagefault. Fix it by setting ctx->fp_used = true for exception boundary programs as fp is always saved in such programs. Fixes: 5d4fa9ec5643 ("bpf, arm64: Avoid blindly saving/restoring all callee-saved registers") Signed-off-by: Puranjay Mohan Signed-off-by: Daniel Borkmann Acked-by: Xu Kuohai Link: https://lore.kernel.org/bpf/20250722133410.54161-2-puranjay@kernel.org --- diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index 89b1b8c248c6..97ab651c0bd5 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -412,6 +412,7 @@ static void push_callee_regs(struct jit_ctx *ctx) emit(A64_PUSH(A64_R(23), A64_R(24), A64_SP), ctx); emit(A64_PUSH(A64_R(25), A64_R(26), A64_SP), ctx); emit(A64_PUSH(A64_R(27), A64_R(28), A64_SP), ctx); + ctx->fp_used = true; } else { find_used_callee_regs(ctx); for (i = 0; i + 1 < ctx->nr_used_callee_reg; i += 2) {