lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CAADnVQ+7qB44dGT4xkMPRrxNJrY-MFVU8E=jPiD+_CXvL6Didw@mail.gmail.com>
Date: Wed, 24 Jan 2024 18:34:52 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Brett Creeley <bcreeley@....com>
Cc: Maciej Fijalkowski <maciej.fijalkowski@...el.com>, bpf <bpf@...r.kernel.org>, 
	Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, Network Development <netdev@...r.kernel.org>, 
	"Karlsson, Magnus" <magnus.karlsson@...el.com>, Björn Töpel <bjorn@...nel.org>, 
	Eelco Chaudron <echaudro@...hat.com>, Lorenzo Bianconi <lorenzo@...nel.org>, 
	Martin KaFai Lau <martin.lau@...ux.dev>, "Sarkar, Tirthendu" <tirthendu.sarkar@...el.com>, 
	John Fastabend <john.fastabend@...il.com>, Simon Horman <horms@...nel.org>, 
	Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH v6 bpf 04/11] ice: work on pre-XDP prog frag count

On Wed, Jan 24, 2024 at 6:26 PM Brett Creeley <bcreeley@....com> wrote:
>
>
>
> On 1/24/2024 11:15 AM, Maciej Fijalkowski wrote:
> > Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
> >
> >
> > Fix an OOM panic in XDP_DRV mode when a XDP program shrinks a
> > multi-buffer packet by 4k bytes and then redirects it to an AF_XDP
> > socket.
> >
> > Since support for handling multi-buffer frames was added to XDP, usage
> > of bpf_xdp_adjust_tail() helper within XDP program can free the page
> > that given fragment occupies and in turn decrease the fragment count
> > within skb_shared_info that is embedded in xdp_buff struct. In current
> > ice driver codebase, it can become problematic when page recycling logic
> > decides not to reuse the page. In such case, __page_frag_cache_drain()
> > is used with ice_rx_buf::pagecnt_bias that was not adjusted after
> > refcount of page was changed by XDP prog which in turn does not drain
> > the refcount to 0 and page is never freed.
> >
> > To address this, let us store the count of frags before the XDP program
> > was executed on Rx ring struct. This will be used to compare with
> > current frag count from skb_shared_info embedded in xdp_buff. A smaller
> > value in the latter indicates that XDP prog freed frag(s). Then, for
> > given delta decrement pagecnt_bias for XDP_DROP verdict.
> >
> > While at it, let us also handle the EOP frag within
> > ice_set_rx_bufs_act() to make our life easier, so all of the adjustments
> > needed to be applied against freed frags are performed in the single
> > place.
> >
> > Fixes: 2fba7dc5157b ("ice: Add support for XDP multi-buffer on Rx side")
> > Acked-by: Magnus Karlsson <magnus.karlsson@...el.com>
> > Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> > ---
> >   drivers/net/ethernet/intel/ice/ice_txrx.c     | 14 ++++++---
> >   drivers/net/ethernet/intel/ice/ice_txrx.h     |  1 +
> >   drivers/net/ethernet/intel/ice/ice_txrx_lib.h | 31 +++++++++++++------
> >   3 files changed, 32 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.c b/drivers/net/ethernet/intel/ice/ice_txrx.c
> > index 74d13cc5a3a7..0c9b4aa8a049 100644
> > --- a/drivers/net/ethernet/intel/ice/ice_txrx.c
> > +++ b/drivers/net/ethernet/intel/ice/ice_txrx.c
> > @@ -603,9 +603,7 @@ ice_run_xdp(struct ice_rx_ring *rx_ring, struct xdp_buff *xdp,
> >                  ret = ICE_XDP_CONSUMED;
> >          }
> >   exit:
> > -       rx_buf->act = ret;
> > -       if (unlikely(xdp_buff_has_frags(xdp)))
> > -               ice_set_rx_bufs_act(xdp, rx_ring, ret);
> > +       ice_set_rx_bufs_act(xdp, rx_ring, ret);
> >   }
> >
> >   /**
> > @@ -893,14 +891,17 @@ ice_add_xdp_frag(struct ice_rx_ring *rx_ring, struct xdp_buff *xdp,
> >          }
> >
> >          if (unlikely(sinfo->nr_frags == MAX_SKB_FRAGS)) {
> > -               if (unlikely(xdp_buff_has_frags(xdp)))
> > -                       ice_set_rx_bufs_act(xdp, rx_ring, ICE_XDP_CONSUMED);
> > +               ice_set_rx_bufs_act(xdp, rx_ring, ICE_XDP_CONSUMED);
> >                  return -ENOMEM;
> >          }
> >
> >          __skb_fill_page_desc_noacc(sinfo, sinfo->nr_frags++, rx_buf->page,
> >                                     rx_buf->page_offset, size);
> >          sinfo->xdp_frags_size += size;
> > +       /* remember frag count before XDP prog execution; bpf_xdp_adjust_tail()
> > +        * can pop off frags but driver has to handle it on its own
> > +        */
> > +       rx_ring->nr_frags = sinfo->nr_frags;
> >
> >          if (page_is_pfmemalloc(rx_buf->page))
> >                  xdp_buff_set_frag_pfmemalloc(xdp);
> > @@ -1251,6 +1252,7 @@ int ice_clean_rx_irq(struct ice_rx_ring *rx_ring, int budget)
> >
> >                  xdp->data = NULL;
> >                  rx_ring->first_desc = ntc;
> > +               rx_ring->nr_frags = 0;
> >                  continue;
> >   construct_skb:
> >                  if (likely(ice_ring_uses_build_skb(rx_ring)))
> > @@ -1266,10 +1268,12 @@ int ice_clean_rx_irq(struct ice_rx_ring *rx_ring, int budget)
> >                                                      ICE_XDP_CONSUMED);
> >                          xdp->data = NULL;
> >                          rx_ring->first_desc = ntc;
> > +                       rx_ring->nr_frags = 0;
> >                          break;
> >                  }
> >                  xdp->data = NULL;
> >                  rx_ring->first_desc = ntc;
> > +               rx_ring->nr_frags = 0;
> >
> >                  stat_err_bits = BIT(ICE_RX_FLEX_DESC_STATUS0_RXE_S);
> >                  if (unlikely(ice_test_staterr(rx_desc->wb.status_error0,
> > diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.h b/drivers/net/ethernet/intel/ice/ice_txrx.h
> > index b3379ff73674..af955b0e5dc5 100644
> > --- a/drivers/net/ethernet/intel/ice/ice_txrx.h
> > +++ b/drivers/net/ethernet/intel/ice/ice_txrx.h
> > @@ -358,6 +358,7 @@ struct ice_rx_ring {
> >          struct ice_tx_ring *xdp_ring;
> >          struct ice_rx_ring *next;       /* pointer to next ring in q_vector */
> >          struct xsk_buff_pool *xsk_pool;
> > +       u32 nr_frags;
> >          dma_addr_t dma;                 /* physical address of ring */
> >          u16 rx_buf_len;
> >          u8 dcb_tc;                      /* Traffic class of ring */
> > diff --git a/drivers/net/ethernet/intel/ice/ice_txrx_lib.h b/drivers/net/ethernet/intel/ice/ice_txrx_lib.h
> > index 762047508619..afcead4baef4 100644
> > --- a/drivers/net/ethernet/intel/ice/ice_txrx_lib.h
> > +++ b/drivers/net/ethernet/intel/ice/ice_txrx_lib.h
> > @@ -12,26 +12,39 @@
> >    * act: action to store onto Rx buffers related to XDP buffer parts
> >    *
> >    * Set action that should be taken before putting Rx buffer from first frag
> > - * to one before last. Last one is handled by caller of this function as it
> > - * is the EOP frag that is currently being processed. This function is
> > - * supposed to be called only when XDP buffer contains frags.
> > + * to the last.
> >    */
> >   static inline void
> >   ice_set_rx_bufs_act(struct xdp_buff *xdp, const struct ice_rx_ring *rx_ring,
> >                      const unsigned int act)
> >   {
> > -       const struct skb_shared_info *sinfo = xdp_get_shared_info_from_buff(xdp);
> > -       u32 first = rx_ring->first_desc;
> > -       u32 nr_frags = sinfo->nr_frags;
> > +       u32 sinfo_frags = xdp_get_shared_info_from_buff(xdp)->nr_frags;
> > +       u32 nr_frags = rx_ring->nr_frags + 1;
> > +       u32 idx = rx_ring->first_desc;
> >          u32 cnt = rx_ring->count;
> >          struct ice_rx_buf *buf;
> >
> >          for (int i = 0; i < nr_frags; i++) {
> > -               buf = &rx_ring->rx_buf[first];
> > +               buf = &rx_ring->rx_buf[idx];
> >                  buf->act = act;
> >
> > -               if (++first == cnt)
> > -                       first = 0;
> > +               if (++idx == cnt)
> > +                       idx = 0;
> > +       }
> > +
> > +       /* adjust pagecnt_bias on frags freed by XDP prog */
> > +       if (sinfo_frags < rx_ring->nr_frags && act == ICE_XDP_CONSUMED) {
> > +               u32 delta = rx_ring->nr_frags - sinfo_frags;
> > +
> > +               while (delta) {
> > +                       if (idx == 0)
> > +                               idx = cnt - 1;
> > +                       else
> > +                               idx--;
> > +                       buf = &rx_ring->rx_buf[idx];
> > +                       buf->pagecnt_bias--;
> > +                       delta--;
> > +               }
>
> Nit, but the function name ice_set_rx_bufs_act() doesn't completely
> align with what it's doing anymore due to the additional pagecnt_bias
> changes.

The patch set was applied. Please advise whether this can stay as-is
or follow up is absolutely necessary.

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ