When testing XDP programs with LIVE_FRAMES mode, if the metalen is set to >= (XDP_PACKET_HEADROOM - sizeof(struct xdp_frame)), there won't be enough space for the xdp_frame conversion in xdp_update_frame_from_buff(). Additionally, the xdp_frame structure may be filled with user-provided data, which can lead to a memory access vulnerability when converting to skb.
This fix reverts to the original version and ensures data_hard_start correctly points to the xdp_frame structure, eliminating the security risk. Reported-by: Yinhao Hu <[email protected]> Reported-by: Kaiyan Mei <[email protected]> Reviewed-by: Dongliang Mu <[email protected]> Fixes: 294635a8165a ("bpf, test_run: fix &xdp_frame misplacement for LIVE_FRAMES") Signed-off-by: KaFai Wan <[email protected]> --- net/bpf/test_run.c | 23 +++++++++---------- .../bpf/prog_tests/xdp_do_redirect.c | 6 ++--- 2 files changed, 14 insertions(+), 15 deletions(-) diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c index 655efac6f133..00234eba7c76 100644 --- a/net/bpf/test_run.c +++ b/net/bpf/test_run.c @@ -90,11 +90,9 @@ static bool bpf_test_timer_continue(struct bpf_test_timer *t, int iterations, struct xdp_page_head { struct xdp_buff orig_ctx; struct xdp_buff ctx; - union { - /* ::data_hard_start starts here */ - DECLARE_FLEX_ARRAY(struct xdp_frame, frame); - DECLARE_FLEX_ARRAY(u8, data); - }; + /* ::data_hard_start starts here */ + struct xdp_frame frame; + DECLARE_FLEX_ARRAY(u8, data); }; struct xdp_test_data { @@ -131,10 +129,11 @@ static void xdp_test_run_init_page(netmem_ref netmem, void *arg) frm_len = orig_ctx->data_end - orig_ctx->data_meta; meta_len = orig_ctx->data - orig_ctx->data_meta; headroom -= meta_len; + headroom += sizeof(head->frame); new_ctx = &head->ctx; - frm = head->frame; - data = head->data; + frm = &head->frame; + data = frm; memcpy(data + headroom, orig_ctx->data_meta, frm_len); xdp_init_buff(new_ctx, TEST_XDP_FRAME_SIZE, &xdp->rxq); @@ -215,8 +214,8 @@ static bool frame_was_changed(const struct xdp_page_head *head) * i.e. has the highest chances to be overwritten. If those two are * untouched, it's most likely safe to skip the context reset. */ - return head->frame->data != head->orig_ctx.data || - head->frame->flags != head->orig_ctx.flags; + return head->frame.data != head->orig_ctx.data || + head->frame.flags != head->orig_ctx.flags; } static bool ctx_was_changed(struct xdp_page_head *head) @@ -234,8 +233,8 @@ static void reset_ctx(struct xdp_page_head *head) head->ctx.data = head->orig_ctx.data; head->ctx.data_meta = head->orig_ctx.data_meta; head->ctx.data_end = head->orig_ctx.data_end; - xdp_update_frame_from_buff(&head->ctx, head->frame); - head->frame->mem_type = head->orig_ctx.rxq->mem.type; + xdp_update_frame_from_buff(&head->ctx, &head->frame); + head->frame.mem_type = head->orig_ctx.rxq->mem.type; } static int xdp_recv_frames(struct xdp_frame **frames, int nframes, @@ -301,7 +300,7 @@ static int xdp_test_run_batch(struct xdp_test_data *xdp, struct bpf_prog *prog, head = phys_to_virt(page_to_phys(page)); reset_ctx(head); ctx = &head->ctx; - frm = head->frame; + frm = &head->frame; xdp->frame_cnt++; act = bpf_prog_run_xdp(prog, ctx); diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_do_redirect.c b/tools/testing/selftests/bpf/prog_tests/xdp_do_redirect.c index dd34b0cc4b4e..f7615c265e6e 100644 --- a/tools/testing/selftests/bpf/prog_tests/xdp_do_redirect.c +++ b/tools/testing/selftests/bpf/prog_tests/xdp_do_redirect.c @@ -59,12 +59,12 @@ static int attach_tc_prog(struct bpf_tc_hook *hook, int fd) /* The maximum permissible size is: PAGE_SIZE - sizeof(struct xdp_page_head) - * SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) - XDP_PACKET_HEADROOM = - * 3408 bytes for 64-byte cacheline and 3216 for 256-byte one. + * 3368 bytes for 64-byte cacheline and 3216 for 256-byte one. */ #if defined(__s390x__) -#define MAX_PKT_SIZE 3216 +#define MAX_PKT_SIZE 3176 #else -#define MAX_PKT_SIZE 3408 +#define MAX_PKT_SIZE 3368 #endif #define PAGE_SIZE_4K 4096 -- 2.43.0
