linux-kernel - Re: [syzbot] [mm?] [usb?] WARNING in __alloc

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Message-ID: <20250920025550.7294-1-hdanton@sina.com>
Date: Sat, 20 Sep 2025 10:55:49 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+5a2250fd91b28106c37b@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [mm?] [usb?] WARNING in __alloc_skb (4)

> Date: Wed, 27 Aug 2025 14:55:31 -0700	[thread overview]
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    7fa4d8dc380f Add linux-next specific files for 20250821
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=11fecc42580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=ae76068823a236b3
> dashboard link: https://syzkaller.appspot.com/bug?extid=5a2250fd91b28106c37b
> compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14c94858580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=108ea7bc580000

#syz test linux-next master

--- x/net/core/skbuff.c
+++ y/net/core/skbuff.c
@@ -594,6 +594,10 @@ static void *kmalloc_reserve(unsigned in
 	 */
 	*size = (unsigned int)obj_size;
 
+	if (obj_size > (PAGE_SIZE << MAX_PAGE_ORDER)) {
+		obj = NULL;
+		goto out;
+	}
 	/*
 	 * Try a regular allocation, when that fails and we're not entitled
 	 * to the reserves, fail.
@@ -657,7 +661,7 @@ struct sk_buff *__alloc_skb(unsigned int
 	    likely(node == NUMA_NO_NODE || node == numa_mem_id()))
 		skb = napi_skb_cache_get();
 	else
-		skb = kmem_cache_alloc_node(cache, gfp_mask & ~GFP_DMA, node);
+		skb = kmem_cache_alloc_node(cache, gfp_mask & ~(GFP_DMA | __GFP_HIGHMEM), node);
 	if (unlikely(!skb))
 		return NULL;
 	prefetchw(skb);
--