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@xxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: syzbot+5ae46b237278e2369cac@xxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: syzbot+c1e04a422bbc0f0f2921@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 401cb7dae8130 ("net: Reference bpf_redirect_info via task_struct on PREEMPT_RT.")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
On 2024-07-04 07:24:33 [-0700], Jakub Kicinski wrote:
> LG, but can I bother you for a repost? the subject tag is typo'ed
> (net-net vs net-next) and our CI put this on top of net, since it
> applies. But it doesn't build on top of net.
> Feel free to repost without any wait.
I am sorry for the trouble.
v2…v3:
- Repost due to typo in subject.
v1…v2:
- Add the wrapper to do_xdp_generic().
- Remove the wrapper from tun_get_user() where it was used for a
single do_xdp_generic() invocation.
drivers/net/tun.c | 7 +++++++
net/core/dev.c | 5 +++++
2 files changed, 12 insertions(+)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 9254bca2813dc..9b24861464bc6 100644
--- 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 = ¤t->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 385c4091aa775..73e5af6943c39 100644
--- 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;
}
--
2.45.2
