linux-kernel - [PATCH net v1] net: netmem: fix skb_ensure

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Message-ID: <20250615200733.520113-1-almasrymina@google.com>
Date: Sun, 15 Jun 2025 20:07:33 +0000
From: Mina Almasry <almasrymina@...gle.com>
To: netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: Mina Almasry <almasrymina@...gle.com>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Simon Horman <horms@...nel.org>, willemb@...gle.com, sdf@...ichev.me, 
	asml.silence@...il.com
Subject: [PATCH net v1] net: netmem: fix skb_ensure_writable with unreadable skbs

skb_ensure_writable should succeed when it's trying to write to the
header of the unreadable skbs, so it doesn't need an unconditional
skb_frags_readable check. The preceding pskb_may_pull() call will
succeed if write_len is within the head and fail if we're trying to
write to the unreadable payload, so we don't need an additional check.

Removing this check restores DSCP functionality with unreadable skbs as
it's called from dscp_tg.

Cc: willemb@...gle.com
Cc: sdf@...ichev.me
Cc: asml.silence@...il.com
Fixes: 65249feb6b3d ("net: add support for skbs with unreadable frags")
Signed-off-by: Mina Almasry <almasrymina@...gle.com>
---
 net/core/skbuff.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 85fc82f72d26..d6420b74ea9c 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -6261,9 +6261,6 @@ int skb_ensure_writable(struct sk_buff *skb, unsigned int write_len)
 	if (!pskb_may_pull(skb, write_len))
 		return -ENOMEM;
 
-	if (!skb_frags_readable(skb))
-		return -EFAULT;
-
 	if (!skb_cloned(skb) || skb_clone_writable(skb, write_len))
 		return 0;
 

base-commit: 5466491c9e3309ed5c7adbb8fad6e93fcc9a8fe9
-- 
2.50.0.rc1.591.g9c95f17f64-goog