Re: [PATCH net v3] net: esp: fix bad handling of pages from page_pool

[Dragos Tatulea <dtatulea@nvidia.com>]

Hi Ilias,

On Mon, 2024-03-11 at 10:43 +0200, Ilias Apalodimas wrote:
> Hi Dragos,
> 
> On Fri, 8 Mar 2024 at 17:27, Dragos Tatulea <dtatulea@nvidia.com> wrote:
> > 
> > When the skb is reorganized during esp_output (!esp->inline), the pages
> > coming from the original skb fragments are supposed to be released back
> > to the system through put_page.
> >  But if the skb fragment pages are
> > originating from a page_pool, calling put_page on them will trigger a
> > page_pool leak which will eventually result in a crash.
> > 
> 
> Indeed if you call put_page, you will leak a page. But won't that skb
> eventually be freed by skb_free_head()?
> 
I don't think it will: if you look at esp_output_tail (!esp->inplace case), the
skb frags are put on the sg list and then the skb is cut off to have a single
frag (with a "regular" page from x->xfrag). So if the pages from the old
fragments are not freed here they will leak altogether. 

Thanks,
Dragos

> Thanks
> /Ilias
> 
> > This leak can be easily observed when using CONFIG_DEBUG_VM and doing
> > ipsec + gre (non offloaded) forwarding:
> > 
> >   BUG: Bad page state in process ksoftirqd/16  pfn:1451b6
> >   page:00000000de2b8d32 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1451b6000 pfn:0x1451b6
> >   flags: 0x200000000000000(node=0|zone=2)
> >   page_type: 0xffffffff()
> >   raw: 0200000000000000 dead000000000040 ffff88810d23c000 0000000000000000
> >   raw: 00000001451b6000 0000000000000001 00000000ffffffff 0000000000000000
> >   page dumped because: page_pool leak
> >   Modules linked in: ip_gre gre mlx5_ib mlx5_core xt_conntrack xt_MASQUERADE nf_conntrack_netlink nfnetlink iptable_nat nf_nat xt_addrtype br_netfilter rpcrdma rdma_ucm ib_iser libiscsi scsi_transport_iscsi ib_umad rdma_cm ib_ipoib iw_cm ib_cm ib_uverbs ib_core overlay zram zsmalloc fuse [last unloaded: mlx5_core]
> >   CPU: 16 PID: 96 Comm: ksoftirqd/16 Not tainted 6.8.0-rc4+ #22
> >   Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
> >   Call Trace:
> >    <TASK>
> >    dump_stack_lvl+0x36/0x50
> >    bad_page+0x70/0xf0
> >    free_unref_page_prepare+0x27a/0x460
> >    free_unref_page+0x38/0x120
> >    esp_ssg_unref.isra.0+0x15f/0x200
> >    esp_output_tail+0x66d/0x780
> >    esp_xmit+0x2c5/0x360
> >    validate_xmit_xfrm+0x313/0x370
> >    ? validate_xmit_skb+0x1d/0x330
> >    validate_xmit_skb_list+0x4c/0x70
> >    sch_direct_xmit+0x23e/0x350
> >    __dev_queue_xmit+0x337/0xba0
> >    ? nf_hook_slow+0x3f/0xd0
> >    ip_finish_output2+0x25e/0x580
> >    iptunnel_xmit+0x19b/0x240
> >    ip_tunnel_xmit+0x5fb/0xb60
> >    ipgre_xmit+0x14d/0x280 [ip_gre]
> >    dev_hard_start_xmit+0xc3/0x1c0
> >    __dev_queue_xmit+0x208/0xba0
> >    ? nf_hook_slow+0x3f/0xd0
> >    ip_finish_output2+0x1ca/0x580
> >    ip_sublist_rcv_finish+0x32/0x40
> >    ip_sublist_rcv+0x1b2/0x1f0
> >    ? ip_rcv_finish_core.constprop.0+0x460/0x460
> >    ip_list_rcv+0x103/0x130
> >    __netif_receive_skb_list_core+0x181/0x1e0
> >    netif_receive_skb_list_internal+0x1b3/0x2c0
> >    napi_gro_receive+0xc8/0x200
> >    gro_cell_poll+0x52/0x90
> >    __napi_poll+0x25/0x1a0
> >    net_rx_action+0x28e/0x300
> >    __do_softirq+0xc3/0x276
> >    ? sort_range+0x20/0x20
> >    run_ksoftirqd+0x1e/0x30
> >    smpboot_thread_fn+0xa6/0x130
> >    kthread+0xcd/0x100
> >    ? kthread_complete_and_exit+0x20/0x20
> >    ret_from_fork+0x31/0x50
> >    ? kthread_complete_and_exit+0x20/0x20
> >    ret_from_fork_asm+0x11/0x20
> >    </TASK>
> > 
> > The suggested fix is to introduce a new wrapper (skb_page_unref) that
> > covers page refcounting for page_pool pages as well.
> > 
> > Cc: stable@vger.kernel.org
> > Fixes: 6a5bcd84e886 ("page_pool: Allow drivers to hint on SKB recycling")
> > Reported-and-tested-by: Anatoli N.Chechelnickiy <Anatoli.Chechelnickiy@m.interpipe.biz>
> > Reported-by: Ian Kumlien <ian.kumlien@gmail.com>
> > Link: https://lore.kernel.org/netdev/CAA85sZvvHtrpTQRqdaOx6gd55zPAVsqMYk_Lwh4Md5knTq7AyA@mail.gmail.com
> > Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
> > Reviewed-by: Mina Almasry <almasrymina@google.com>
> > Reviewed-by: Jakub Kicinski <kuba@kernel.org>
> > ---
> > Changes in v2:
> > - Fixes in tags.
> > 
> > Changes in v3:
> > - Rebased to ipsec tree.
> > ---
> >  include/linux/skbuff.h | 10 ++++++++++
> >  net/ipv4/esp4.c        |  8 ++++----
> >  net/ipv6/esp6.c        |  8 ++++----
> >  3 files changed, 18 insertions(+), 8 deletions(-)
> > 
> > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> > index 2dde34c29203..d9a1ccfb5708 100644
> > --- a/include/linux/skbuff.h
> > +++ b/include/linux/skbuff.h
> > @@ -3448,6 +3448,16 @@ static inline void skb_frag_ref(struct sk_buff *skb, int f)
> > 
> >  bool napi_pp_put_page(struct page *page, bool napi_safe);
> > 
> > +static inline void
> > +skb_page_unref(const struct sk_buff *skb, struct page *page, bool napi_safe)
> > +{
> > +#ifdef CONFIG_PAGE_POOL
> > +       if (skb->pp_recycle && napi_pp_put_page(page, napi_safe))
> > +               return;
> > +#endif
> > +       put_page(page);
> > +}
> > +
> >  static inline void
> >  napi_frag_unref(skb_frag_t *frag, bool recycle, bool napi_safe)
> >  {
> > diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
> > index 4dd9e5040672..d33d12421814 100644
> > --- a/net/ipv4/esp4.c
> > +++ b/net/ipv4/esp4.c
> > @@ -95,7 +95,7 @@ static inline struct scatterlist *esp_req_sg(struct crypto_aead *aead,
> >                              __alignof__(struct scatterlist));
> >  }
> > 
> > -static void esp_ssg_unref(struct xfrm_state *x, void *tmp)
> > +static void esp_ssg_unref(struct xfrm_state *x, void *tmp, struct sk_buff *skb)
> >  {
> >         struct crypto_aead *aead = x->data;
> >         int extralen = 0;
> > @@ -114,7 +114,7 @@ static void esp_ssg_unref(struct xfrm_state *x, void *tmp)
> >          */
> >         if (req->src != req->dst)
> >                 for (sg = sg_next(req->src); sg; sg = sg_next(sg))
> > -                       put_page(sg_page(sg));
> > +                       skb_page_unref(skb, sg_page(sg), false);
> >  }
> > 
> >  #ifdef CONFIG_INET_ESPINTCP
> > @@ -260,7 +260,7 @@ static void esp_output_done(void *data, int err)
> >         }
> > 
> >         tmp = ESP_SKB_CB(skb)->tmp;
> > -       esp_ssg_unref(x, tmp);
> > +       esp_ssg_unref(x, tmp, skb);
> >         kfree(tmp);
> > 
> >         if (xo && (xo->flags & XFRM_DEV_RESUME)) {
> > @@ -639,7 +639,7 @@ int esp_output_tail(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *
> >         }
> > 
> >         if (sg != dsg)
> > -               esp_ssg_unref(x, tmp);
> > +               esp_ssg_unref(x, tmp, skb);
> > 
> >         if (!err && x->encap && x->encap->encap_type == TCP_ENCAP_ESPINTCP)
> >                 err = esp_output_tail_tcp(x, skb);
> > diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c
> > index 6e6efe026cdc..7371886d4f9f 100644
> > --- a/net/ipv6/esp6.c
> > +++ b/net/ipv6/esp6.c
> > @@ -112,7 +112,7 @@ static inline struct scatterlist *esp_req_sg(struct crypto_aead *aead,
> >                              __alignof__(struct scatterlist));
> >  }
> > 
> > -static void esp_ssg_unref(struct xfrm_state *x, void *tmp)
> > +static void esp_ssg_unref(struct xfrm_state *x, void *tmp, struct sk_buff *skb)
> >  {
> >         struct crypto_aead *aead = x->data;
> >         int extralen = 0;
> > @@ -131,7 +131,7 @@ static void esp_ssg_unref(struct xfrm_state *x, void *tmp)
> >          */
> >         if (req->src != req->dst)
> >                 for (sg = sg_next(req->src); sg; sg = sg_next(sg))
> > -                       put_page(sg_page(sg));
> > +                       skb_page_unref(skb, sg_page(sg), false);
> >  }
> > 
> >  #ifdef CONFIG_INET6_ESPINTCP
> > @@ -294,7 +294,7 @@ static void esp_output_done(void *data, int err)
> >         }
> > 
> >         tmp = ESP_SKB_CB(skb)->tmp;
> > -       esp_ssg_unref(x, tmp);
> > +       esp_ssg_unref(x, tmp, skb);
> >         kfree(tmp);
> > 
> >         esp_output_encap_csum(skb);
> > @@ -677,7 +677,7 @@ int esp6_output_tail(struct xfrm_state *x, struct sk_buff *skb, struct esp_info
> >         }
> > 
> >         if (sg != dsg)
> > -               esp_ssg_unref(x, tmp);
> > +               esp_ssg_unref(x, tmp, skb);
> > 
> >         if (!err && x->encap && x->encap->encap_type == TCP_ENCAP_ESPINTCP)
> >                 err = esp_output_tail_tcp(x, skb);
> > --
> > 2.42.0
> >