[PATCH] bpf, arm64: Fix address emission with tag-based KASAN enabled
Xu Kuohai
xukuohai at huaweicloud.com
Sat Oct 19 02:24:42 PDT 2024
On 10/19/2024 6:16 AM, Peter Collingbourne wrote:
> When BPF_TRAMP_F_CALL_ORIG is enabled, the address of a bpf_tramp_image
> struct on the stack is passed during the size calculation pass and
> an address on the heap is passed during code generation. This may
> cause a heap buffer overflow if the heap address is tagged because
> emit_a64_mov_i64() will emit longer code than it did during the size
> calculation pass. The same problem could occur without tag-based
> KASAN if one of the 16-bit words of the stack address happened to
> be all-ones during the size calculation pass. Fix the problem by
> assuming the worst case (4 instructions) when calculating the size
> of the bpf_tramp_image address emission.
>
> Fixes: 19d3c179a377 ("bpf, arm64: Fix trampoline for BPF_TRAMP_F_CALL_ORIG")
> Signed-off-by: Peter Collingbourne <pcc at google.com>
> Link: https://linux-review.googlesource.com/id/I1496f2bc24fba7a1d492e16e2b94cf43714f2d3c
> Cc: stable at vger.kernel.org
> ---
> arch/arm64/net/bpf_jit_comp.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
> index 8bbd0b20136a8..5db82bfc9dc11 100644
> --- a/arch/arm64/net/bpf_jit_comp.c
> +++ b/arch/arm64/net/bpf_jit_comp.c
> @@ -2220,7 +2220,11 @@ static int prepare_trampoline(struct jit_ctx *ctx, struct bpf_tramp_image *im,
> emit(A64_STR64I(A64_R(20), A64_SP, regs_off + 8), ctx);
>
> if (flags & BPF_TRAMP_F_CALL_ORIG) {
> - emit_a64_mov_i64(A64_R(0), (const u64)im, ctx);
> + /* for the first pass, assume the worst case */
> + if (!ctx->image)
> + ctx->idx += 4;
> + else
> + emit_a64_mov_i64(A64_R(0), (const u64)im, ctx);
> emit_call((const u64)__bpf_tramp_enter, ctx);
> }
>
> @@ -2264,7 +2268,11 @@ static int prepare_trampoline(struct jit_ctx *ctx, struct bpf_tramp_image *im,
>
> if (flags & BPF_TRAMP_F_CALL_ORIG) {
> im->ip_epilogue = ctx->ro_image + ctx->idx;
> - emit_a64_mov_i64(A64_R(0), (const u64)im, ctx);
> + /* for the first pass, assume the worst case */
> + if (!ctx->image)
> + ctx->idx += 4;
> + else
> + emit_a64_mov_i64(A64_R(0), (const u64)im, ctx);
> emit_call((const u64)__bpf_tramp_exit, ctx);
> }
>
Acked-by: Xu Kuohai <xukuohai at huawei.com>
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