This is a note to let you know that I've just added the patch titled bpf: Make sure internal and UAPI bpf_redirect flags don't overlap to the 6.11-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: bpf-make-sure-internal-and-uapi-bpf_redirect-flags-d.patch and it can be found in the queue-6.11 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 9c555d2aae4d28bc57fd2743b6013581e1d7c0b2 Author: Toke Høiland-Jørgensen <toke@xxxxxxxxxx> Date: Fri Sep 20 14:56:24 2024 +0200 bpf: Make sure internal and UAPI bpf_redirect flags don't overlap [ Upstream commit 09d88791c7cd888d5195c84733caf9183dcfbd16 ] The bpf_redirect_info is shared between the SKB and XDP redirect paths, and the two paths use the same numeric flag values in the ri->flags field (specifically, BPF_F_BROADCAST == BPF_F_NEXTHOP). This means that if skb bpf_redirect_neigh() is used with a non-NULL params argument and, subsequently, an XDP redirect is performed using the same bpf_redirect_info struct, the XDP path will get confused and end up crashing, which syzbot managed to trigger. With the stack-allocated bpf_redirect_info, the structure is no longer shared between the SKB and XDP paths, so the crash doesn't happen anymore. However, different code paths using identically-numbered flag values in the same struct field still seems like a bit of a mess, so this patch cleans that up by moving the flag definitions together and redefining the three flags in BPF_F_REDIRECT_INTERNAL to not overlap with the flags used for XDP. It also adds a BUILD_BUG_ON() check to make sure the overlap is not re-introduced by mistake. Fixes: e624d4ed4aa8 ("xdp: Extend xdp_redirect_map with broadcast support") Reported-by: syzbot+cca39e6e84a367a7e6f6@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx> Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx> Acked-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx> Closes: https://syzkaller.appspot.com/bug?extid=cca39e6e84a367a7e6f6 Link: https://lore.kernel.org/bpf/20240920125625.59465-1-toke@xxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 35bcf52dbc652..fea4bca4066c1 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -6046,11 +6046,6 @@ enum { BPF_F_MARK_ENFORCE = (1ULL << 6), }; -/* BPF_FUNC_clone_redirect and BPF_FUNC_redirect flags. */ -enum { - BPF_F_INGRESS = (1ULL << 0), -}; - /* BPF_FUNC_skb_set_tunnel_key and BPF_FUNC_skb_get_tunnel_key flags. */ enum { BPF_F_TUNINFO_IPV6 = (1ULL << 0), @@ -6197,10 +6192,12 @@ enum { BPF_F_BPRM_SECUREEXEC = (1ULL << 0), }; -/* Flags for bpf_redirect_map helper */ +/* Flags for bpf_redirect and bpf_redirect_map helpers */ enum { - BPF_F_BROADCAST = (1ULL << 3), - BPF_F_EXCLUDE_INGRESS = (1ULL << 4), + BPF_F_INGRESS = (1ULL << 0), /* used for skb path */ + BPF_F_BROADCAST = (1ULL << 3), /* used for XDP path */ + BPF_F_EXCLUDE_INGRESS = (1ULL << 4), /* used for XDP path */ +#define BPF_F_REDIRECT_FLAGS (BPF_F_INGRESS | BPF_F_BROADCAST | BPF_F_EXCLUDE_INGRESS) }; #define __bpf_md_ptr(type, name) \ diff --git a/net/core/filter.c b/net/core/filter.c index 0e719c7c43bb7..b7a5f525e65b8 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2437,9 +2437,9 @@ static int __bpf_redirect_neigh(struct sk_buff *skb, struct net_device *dev, /* Internal, non-exposed redirect flags. */ enum { - BPF_F_NEIGH = (1ULL << 1), - BPF_F_PEER = (1ULL << 2), - BPF_F_NEXTHOP = (1ULL << 3), + BPF_F_NEIGH = (1ULL << 16), + BPF_F_PEER = (1ULL << 17), + BPF_F_NEXTHOP = (1ULL << 18), #define BPF_F_REDIRECT_INTERNAL (BPF_F_NEIGH | BPF_F_PEER | BPF_F_NEXTHOP) }; @@ -2449,6 +2449,8 @@ BPF_CALL_3(bpf_clone_redirect, struct sk_buff *, skb, u32, ifindex, u64, flags) struct sk_buff *clone; int ret; + BUILD_BUG_ON(BPF_F_REDIRECT_INTERNAL & BPF_F_REDIRECT_FLAGS); + if (unlikely(flags & (~(BPF_F_INGRESS) | BPF_F_REDIRECT_INTERNAL))) return -EINVAL;