linux-kernel - Re: [syzbot] [net?] general protection fault in put

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Message-ID: <20241218231457.288-1-hdanton@sina.com>
Date: Thu, 19 Dec 2024 07:14:56 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+38a095a81f30d82884c1@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [net?] general protection fault in put_page (4)

On Tue, Dec 17, 2024 at 6:03 PM
> syzbot found the following issue on:
>
> HEAD commit:    78d4f34e2115 Linux 6.13-rc3
> git tree:       upstream
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13f502df980000

#syz test

--- x/net/core/skbuff.c
+++ y/net/core/skbuff.c
@@ -1099,13 +1099,22 @@ static void skb_free_head(struct sk_buff
 	}
 }
 
+static DEFINE_SPINLOCK(skb_release_data_lock);
 static void skb_release_data(struct sk_buff *skb, enum skb_drop_reason reason)
 {
 	struct skb_shared_info *shinfo = skb_shinfo(skb);
 	int i;
+	unsigned long flg;
 
 	if (!skb_data_unref(skb, shinfo))
-		goto exit;
+		return;
+	spin_lock_irqsave(&skb_release_data_lock, flg);
+	if ((1 << 6) & shinfo->flags) {
+		spin_unlock_irqrestore(&skb_release_data_lock, flg);
+		return;
+	}
+	shinfo->flags |= (1 << 6);
+	spin_unlock_irqrestore(&skb_release_data_lock, flg);
 
 	if (skb_zcopy(skb)) {
 		bool skip_unref = shinfo->flags & SKBFL_MANAGED_FRAG_REFS;
--