path: root/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
diff options
authorToke Høiland-Jørgensen <toke@redhat.com>2021-06-24 18:06:08 +0200
committerDaniel Borkmann <daniel@iogearbox.net>2021-06-24 19:46:25 +0200
commit2f1e432d339c5fed435adf521cae392755721050 (patch)
tree626683b2ed90859c4ac4edeb3153dd770aab2667 /drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
parent7b6ee873ff20c22af355661b241defa7f6ed7582 (diff)
stmmac: Remove rcu_read_lock() around XDP program invocation
The stmmac driver has 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> Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com> Cc: Alexandre Torgue <alexandre.torgue@foss.st.com> Cc: Jose Abreu <joabreu@synopsys.com> Link: https://lore.kernel.org/bpf/20210624160609.292325-19-toke@redhat.com
Diffstat (limited to 'drivers/net/ethernet/stmicro/stmmac/stmmac_main.c')
1 files changed, 2 insertions, 8 deletions
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 16820873b01d..219535ab2c0c 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -4651,7 +4651,6 @@ static int stmmac_xdp_xmit_back(struct stmmac_priv *priv,
return res;
-/* This function assumes rcu_read_lock() is held by the caller. */
static int __stmmac_xdp_run_prog(struct stmmac_priv *priv,
struct bpf_prog *prog,
struct xdp_buff *xdp)
@@ -4693,17 +4692,14 @@ static struct sk_buff *stmmac_xdp_run_prog(struct stmmac_priv *priv,
struct bpf_prog *prog;
int res;
- rcu_read_lock();
prog = READ_ONCE(priv->xdp_prog);
if (!prog) {
- goto unlock;
+ goto out;
res = __stmmac_xdp_run_prog(priv, prog, xdp);
- rcu_read_unlock();
return ERR_PTR(-res);
@@ -4973,10 +4969,8 @@ read_again:
buf->xdp->data_end = buf->xdp->data + buf1_len;
xsk_buff_dma_sync_for_cpu(buf->xdp, rx_q->xsk_pool);
- rcu_read_lock();
prog = READ_ONCE(priv->xdp_prog);
res = __stmmac_xdp_run_prog(priv, prog, buf->xdp);
- rcu_read_unlock();
switch (res) {