tun: Assign missing bpf_net_context.

During the introduction of struct bpf_net_context handling for
XDP-redirect, the tun driver has been missed.
Jakub also pointed out that there is another call chain to
do_xdp_generic() originating from netif_receive_skb() and drivers may
use it outside from the NAPI context.

Set the bpf_net_context before invoking BPF XDP program within the TUN
driver. Set the bpf_net_context also in do_xdp_generic() if a xdp
program is available.

Reported-by: syzbot+0b5c75599f1d872bea6f@syzkaller.appspotmail.com
Reported-by: syzbot+5ae46b237278e2369cac@syzkaller.appspotmail.com
Reported-by: syzbot+c1e04a422bbc0f0f2921@syzkaller.appspotmail.com
Fixes: 401cb7dae8130 ("net: Reference bpf_redirect_info via task_struct on PREEMPT_RT.")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://patch.msgid.link/20240704144815.j8xQda5r@linutronix.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 9254bca2813dc19f75a395fa0d6a26658ecd6cb9..9b24861464bc65a8bfab3955c6d39e174a44147b 100644 (file)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1661,6 +1661,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
                                     int len, int *skb_xdp)
 {
        struct page_frag *alloc_frag = &current->task_frag;
+       struct bpf_net_context __bpf_net_ctx, *bpf_net_ctx;
        struct bpf_prog *xdp_prog;
        int buflen = SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
        char *buf;
@@ -1700,6 +1701,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
 
        local_bh_disable();
        rcu_read_lock();
+       bpf_net_ctx = bpf_net_ctx_set(&__bpf_net_ctx);
        xdp_prog = rcu_dereference(tun->xdp_prog);
        if (xdp_prog) {
                struct xdp_buff xdp;
@@ -1728,12 +1730,14 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
                pad = xdp.data - xdp.data_hard_start;
                len = xdp.data_end - xdp.data;
        }
+       bpf_net_ctx_clear(bpf_net_ctx);
        rcu_read_unlock();
        local_bh_enable();
 
        return __tun_build_skb(tfile, alloc_frag, buf, buflen, len, pad);
 
 out:
+       bpf_net_ctx_clear(bpf_net_ctx);
        rcu_read_unlock();
        local_bh_enable();
        return NULL;
@@ -2566,6 +2570,7 @@ static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
 
        if (m->msg_controllen == sizeof(struct tun_msg_ctl) &&
            ctl && ctl->type == TUN_MSG_PTR) {
+               struct bpf_net_context __bpf_net_ctx, *bpf_net_ctx;
                struct tun_page tpage;
                int n = ctl->num;
                int flush = 0, queued = 0;
@@ -2574,6 +2579,7 @@ static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
 
                local_bh_disable();
                rcu_read_lock();
+               bpf_net_ctx = bpf_net_ctx_set(&__bpf_net_ctx);
 
                for (i = 0; i < n; i++) {
                        xdp = &((struct xdp_buff *)ctl->ptr)[i];
@@ -2588,6 +2594,7 @@ static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
                if (tfile->napi_enabled && queued > 0)
                        napi_schedule(&tfile->napi);
 
+               bpf_net_ctx_clear(bpf_net_ctx);
                rcu_read_unlock();
                local_bh_enable();
 

diff --git a/net/core/dev.c b/net/core/dev.c
index 385c4091aa7751697aee795b365246c6906dd25e..73e5af6943c39444e0abfec23dbedcb9249f6266 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5126,11 +5126,14 @@ static DEFINE_STATIC_KEY_FALSE(generic_xdp_needed_key);
 
 int do_xdp_generic(struct bpf_prog *xdp_prog, struct sk_buff **pskb)
 {
+       struct bpf_net_context __bpf_net_ctx, *bpf_net_ctx;
+
        if (xdp_prog) {
                struct xdp_buff xdp;
                u32 act;
                int err;
 
+               bpf_net_ctx = bpf_net_ctx_set(&__bpf_net_ctx);
                act = netif_receive_generic_xdp(pskb, &xdp, xdp_prog);
                if (act != XDP_PASS) {
                        switch (act) {
@@ -5144,11 +5147,13 @@ int do_xdp_generic(struct bpf_prog *xdp_prog, struct sk_buff **pskb)
                                generic_xdp_tx(*pskb, xdp_prog);
                                break;
                        }
+                       bpf_net_ctx_clear(bpf_net_ctx);
                        return XDP_DROP;
                }
        }
        return XDP_PASS;
 out_redir:
+       bpf_net_ctx_clear(bpf_net_ctx);
        kfree_skb_reason(*pskb, SKB_DROP_REASON_XDP);
        return XDP_DROP;
 }