net: stmmac: fix rx budget limit check

[ Upstream commit fa02de9 ]

The while loop condition verifies 'count < limit'. Neither value change
before the 'count >= limit' check. As is this check is dead code. But
code inspection reveals a code path that modifies 'count' and then goto
'drain_data' and back to 'read_again'. So there is a need to verify
count value sanity after 'read_again'.

Move 'read_again' up to fix the count limit check.

Fixes: ec22200 ("net: stmmac: Prepare to add Split Header support")
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: Serge Semin <fancer.lancer@gmail.com>
Link: https://lore.kernel.org/r/d9486296c3b6b12ab3a0515fcd47d56447a07bfc.1699897370.git.baruch@tkos.co.il
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -5233,10 +5233,10 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue)
 			len = 0;
 		}
 
+read_again:
 		if (count >= limit)
 			break;
 
-read_again:
 		buf1_len = 0;
 		buf2_len = 0;
 		entry = next_entry;