Re: [PATCH 6.6 v3 2/3] tun: Assign missing bpf_net_context.

[Sasha Levin <sashal@kernel.org>]

[ Sasha's backport helper bot ]

Hi,

Summary of potential issues:
ℹ️ This is part 2/3 of a series
⚠️ Found follow-up fixes in mainline

The upstream commit SHA1 provided is correct: fecef4cd42c689a200bdd39e6fffa71475904bc1

WARNING: Author mismatch between patch and upstream commit:
Backport author: =?utf-8?q?Ricardo_Ca=C3=B1uelo_Navarro?=<rcn@igalia.com>
Commit author: Sebastian Andrzej Siewior<bigeasy@linutronix.de>

Found fixes commits:
9da49aa80d68 tun: Add missing bpf_net_ctx_clear() in do_xdp_generic()

Note: The patch differs from the upstream commit:
---
1:  fecef4cd42c68 ! 1:  d614f795c4a67 tun: Assign missing bpf_net_context.
    @@ Metadata
      ## Commit message ##
         tun: Assign missing bpf_net_context.
     
    +    [ Upstream commit fecef4cd42c689a200bdd39e6fffa71475904bc1 ]
    +
         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
    @@ Commit message
         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>
    +    [rcn: Backport the patch to address minor differences in the context lines.
    +    These differences are introduced by upstream commits
    +    4d2bb0bfe874 ("xdp: rely on skb pointer reference in do_xdp_generic and
    +    netif_receive_generic_xdp") and 7cd1107f48e2a ("bpf, xdp: constify some
    +    bpf_prog * function arguments"), which change the parameters in
    +    do_xdp_generic() and in calls to netif_receive_generic_xdp(),
    +    kfree_skb_reason() and generic_xdp_tx(). These changes aren't
    +    significant to the purpose of the patch.]
    +    Signed-off-by: Ricardo Cañuelo Navarro <rcn@igalia.com>
     
      ## drivers/net/tun.c ##
     @@ drivers/net/tun.c: static struct sk_buff *tun_build_skb(struct tun_struct *tun,
    @@ drivers/net/tun.c: static int tun_sendmsg(struct socket *sock, struct msghdr *m,
      ## net/core/dev.c ##
     @@ net/core/dev.c: static DEFINE_STATIC_KEY_FALSE(generic_xdp_needed_key);
      
    - int do_xdp_generic(struct bpf_prog *xdp_prog, struct sk_buff **pskb)
    + int do_xdp_generic(struct bpf_prog *xdp_prog, struct sk_buff *skb)
      {
     +	struct bpf_net_context __bpf_net_ctx, *bpf_net_ctx;
     +
    @@ net/core/dev.c: static DEFINE_STATIC_KEY_FALSE(generic_xdp_needed_key);
      		int err;
      
     +		bpf_net_ctx = bpf_net_ctx_set(&__bpf_net_ctx);
    - 		act = netif_receive_generic_xdp(pskb, &xdp, xdp_prog);
    + 		act = netif_receive_generic_xdp(skb, &xdp, xdp_prog);
      		if (act != XDP_PASS) {
      			switch (act) {
    -@@ net/core/dev.c: int do_xdp_generic(struct bpf_prog *xdp_prog, struct sk_buff **pskb)
    - 				generic_xdp_tx(*pskb, xdp_prog);
    +@@ net/core/dev.c: int do_xdp_generic(struct bpf_prog *xdp_prog, struct sk_buff *skb)
    + 				generic_xdp_tx(skb, xdp_prog);
      				break;
      			}
     +			bpf_net_ctx_clear(bpf_net_ctx);
    @@ net/core/dev.c: int do_xdp_generic(struct bpf_prog *xdp_prog, struct sk_buff **p
      	return XDP_PASS;
      out_redir:
     +	bpf_net_ctx_clear(bpf_net_ctx);
    - 	kfree_skb_reason(*pskb, SKB_DROP_REASON_XDP);
    + 	kfree_skb_reason(skb, SKB_DROP_REASON_XDP);
      	return XDP_DROP;
      }
---

NOTE: These results are for this patch alone. Full series testing will be
performed when all parts are received.

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-6.6.y        |  Success    |  Success   |