6.15-stable review patch. If anyone has any objections, please let me know.
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From: Puranjay Mohan puranjay@kernel.org
[ Upstream commit b114fcee766d5101eada1aca7bb5fd0a86c89b35 ]
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 puranjay@kernel.org Signed-off-by: Daniel Borkmann daniel@iogearbox.net Acked-by: Xu Kuohai xukuohai@huawei.com Link: https://lore.kernel.org/bpf/20250722133410.54161-2-puranjay@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/net/bpf_jit_comp.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index 634d78422adb..a85236d0afee 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) {