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intel: Remove rcu_read_lock() around XDP program invocation

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The Intel drivers all have rcu_read_lock()/rcu_read_unlock() pairs around
XDP program invocations. However, the actual lifetime of the objects
referred by the XDP program invocation is longer, all the way through to
the call to xdp_do_flush(), making the scope of the rcu_read_lock() too
small. This turns out to be harmless because it all happens in a single
NAPI poll cycle (and thus under local_bh_disable()), but it makes the
rcu_read_lock() misleading.

Rather than extend the scope of the rcu_read_lock(), just get rid of it
entirely. With the addition of RCU annotations to the XDP_REDIRECT map
types that take bh execution into account, lockdep even understands this to
be safe, so there's really no reason to keep it around.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Jesper Dangaard Brouer <brouer@redhat.com> # i40e
Cc: Jesse Brandeburg <jesse.brandeburg@intel.com>
Cc: Tony Nguyen <anthony.l.nguyen@intel.com>
Cc: intel-wired-lan@lists.osuosl.org
Link: https://lore.kernel.org/bpf/20210624160609.292325-12-toke@redhat.com
This commit is contained in:
Toke Høiland-Jørgensen 2021-06-24 18:06:01 +02:00 committed by Daniel Borkmann
parent 547aabcac3
commit 49589b23d5
9 changed files with 3 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/net/ethernet/intel/i40e/i40e_txrx.c
View File

@ -2298,7 +2298,6 @@ static int i40e_run_xdp(struct i40e_ring *rx_ring, struct xdp_buff *xdp)
struct bpf_prog *xdp_prog;
u32 act;
rcu_read_lock();
xdp_prog = READ_ONCE(rx_ring->xdp_prog);
if (!xdp_prog)
@ -2334,7 +2333,6 @@ out_failure:
break;
}
xdp_out:
rcu_read_unlock();
return result;
}

3
drivers/net/ethernet/intel/i40e/i40e_xsk.c
View File

@ -153,7 +153,6 @@ static int i40e_run_xdp_zc(struct i40e_ring *rx_ring, struct xdp_buff *xdp)
struct bpf_prog *xdp_prog;
u32 act;
rcu_read_lock();
/* NB! xdp_prog will always be !NULL, due to the fact that
* this path is enabled by setting an XDP program.
*/
@ -164,7 +163,6 @@ static int i40e_run_xdp_zc(struct i40e_ring *rx_ring, struct xdp_buff *xdp)
err = xdp_do_redirect(rx_ring->netdev, xdp, xdp_prog);
if (err)
goto out_failure;
rcu_read_unlock();
return I40E_XDP_REDIR;
}
@ -188,7 +186,6 @@ out_failure:
result = I40E_XDP_CONSUMED;
break;
}
rcu_read_unlock();
return result;
}

6
drivers/net/ethernet/intel/ice/ice_txrx.c
View File

@ -1135,15 +1135,11 @@ int ice_clean_rx_irq(struct ice_ring *rx_ring, int budget)
xdp.frame_sz = ice_rx_frame_truesize(rx_ring, size);
#endif
rcu_read_lock();
xdp_prog = READ_ONCE(rx_ring->xdp_prog);
if (!xdp_prog) {
rcu_read_unlock();
if (!xdp_prog)
goto construct_skb;
}
xdp_res = ice_run_xdp(rx_ring, &xdp, xdp_prog);
rcu_read_unlock();
if (!xdp_res)
goto construct_skb;
if (xdp_res & (ICE_XDP_TX | ICE_XDP_REDIR)) {

3
drivers/net/ethernet/intel/ice/ice_xsk.c
View File

@ -466,7 +466,6 @@ ice_run_xdp_zc(struct ice_ring *rx_ring, struct xdp_buff *xdp)
struct ice_ring *xdp_ring;
u32 act;
rcu_read_lock();
/* ZC patch is enabled only when XDP program is set,
* so here it can not be NULL
*/
@ -478,7 +477,6 @@ ice_run_xdp_zc(struct ice_ring *rx_ring, struct xdp_buff *xdp)
err = xdp_do_redirect(rx_ring->netdev, xdp, xdp_prog);
if (err)
goto out_failure;
rcu_read_unlock();
return ICE_XDP_REDIR;
}
@ -503,7 +501,6 @@ out_failure:
break;
}
rcu_read_unlock();
return result;
}

2
drivers/net/ethernet/intel/igb/igb_main.c
View File

@ -8381,7 +8381,6 @@ static struct sk_buff *igb_run_xdp(struct igb_adapter *adapter,
struct bpf_prog *xdp_prog;
u32 act;
rcu_read_lock();
xdp_prog = READ_ONCE(rx_ring->xdp_prog);
if (!xdp_prog)
@ -8416,7 +8415,6 @@ out_failure:
break;
}
xdp_out:
rcu_read_unlock();
return ERR_PTR(-result);
}

7
drivers/net/ethernet/intel/igc/igc_main.c
View File

@ -2240,18 +2240,15 @@ static struct sk_buff *igc_xdp_run_prog(struct igc_adapter *adapter,
struct bpf_prog *prog;
int res;
rcu_read_lock();
prog = READ_ONCE(adapter->xdp_prog);
if (!prog) {
res = IGC_XDP_PASS;
goto unlock;
goto out;
}
res = __igc_xdp_run_prog(adapter, prog, xdp);
unlock:
rcu_read_unlock();
out:
return ERR_PTR(-res);
}

2
drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
View File

@ -2199,7 +2199,6 @@ static struct sk_buff *ixgbe_run_xdp(struct ixgbe_adapter *adapter,
struct xdp_frame *xdpf;
u32 act;
rcu_read_lock();
xdp_prog = READ_ONCE(rx_ring->xdp_prog);
if (!xdp_prog)
@ -2237,7 +2236,6 @@ out_failure:
break;
}
xdp_out:
rcu_read_unlock();
return ERR_PTR(-result);
}

3
drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
View File

@ -100,7 +100,6 @@ static int ixgbe_run_xdp_zc(struct ixgbe_adapter *adapter,
struct xdp_frame *xdpf;
u32 act;
rcu_read_lock();
xdp_prog = READ_ONCE(rx_ring->xdp_prog);
act = bpf_prog_run_xdp(xdp_prog, xdp);
@ -108,7 +107,6 @@ static int ixgbe_run_xdp_zc(struct ixgbe_adapter *adapter,
err = xdp_do_redirect(rx_ring->netdev, xdp, xdp_prog);
if (err)
goto out_failure;
rcu_read_unlock();
return IXGBE_XDP_REDIR;
}
@ -134,7 +132,6 @@ out_failure:
result = IXGBE_XDP_CONSUMED;
break;
}
rcu_read_unlock();
return result;
}

2
drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
View File

@ -1054,7 +1054,6 @@ static struct sk_buff *ixgbevf_run_xdp(struct ixgbevf_adapter *adapter,
struct bpf_prog *xdp_prog;
u32 act;
rcu_read_lock();
xdp_prog = READ_ONCE(rx_ring->xdp_prog);
if (!xdp_prog)
@ -1082,7 +1081,6 @@ out_failure:
break;
}
xdp_out:
rcu_read_unlock();
return ERR_PTR(-result);
}