From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3F5503CBE90 for ; Mon, 13 Apr 2026 13:33:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776087205; cv=none; b=VjXFRcBgvkcpz4DeIzmpkN0CV2gpkraS49DgwgRVBSoIng169TfIR2zr+7z/vEzeYuA2jnhfef8UpiMw6PJbsGrh0C6CStU286tZLX428Hh5k8hs1Z3hsCos4htAcXJP1tvaNKjOG9VD21k5JNxO7ZZOyR49iMgSqzJPT/lp64U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776087205; c=relaxed/simple; bh=MMgCXGLZpVUiEhKKnRsDzOVcMoV8U9Zdtn/VieXCJXo=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=ek6lixnQUHVQYiA5+t6ll5lYAjb5Ompz11f7kqPkbrmcW8FuMv7kq2x/06fAq2lj5k7UAC3022PEJIWCXs74xaR6Prwjsq2beYOLIRNxxiK9P80zfF2Y3ALIanf5dME64F2O6cDooF5jZ/x94/3BkO+y7dsqu/lJYuqmWfufTjc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=oEs/vDrU; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="oEs/vDrU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 94411C2BCAF; Mon, 13 Apr 2026 13:33:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1776087204; bh=MMgCXGLZpVUiEhKKnRsDzOVcMoV8U9Zdtn/VieXCJXo=; h=Subject:To:Cc:From:Date:From; b=oEs/vDrUmVMRzFfPyfVNpyRr91gv9PsKjS/kTwTEe7zN18tOXWLL6RaIjUfFEDgeG wLwNjlMl+XV7iJYfNITdKVJlMQDuBrPCWHrRlLHVmqI5KcWqnhNF1xBVQ0k2W/YHKe J/eN9kp452pOECrgWtXKnnOfCFhjHOTymOEZiCjQ= Subject: FAILED: patch "[PATCH] net: skb: fix cross-cache free of KFENCE-allocated skb head" failed to apply to 6.6-stable tree To: jiayuan.chen@linux.dev,antonius@bluedragonsec.com,edumazet@google.com,kuba@kernel.org Cc: From: Date: Mon, 13 Apr 2026 15:13:39 +0200 Message-ID: <2026041339-celery-ribbon-dc62@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 0f42e3f4fe2a58394e37241d02d9ca6ab7b7d516 # git commit -s git send-email --to '' --in-reply-to '2026041339-celery-ribbon-dc62@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 0f42e3f4fe2a58394e37241d02d9ca6ab7b7d516 Mon Sep 17 00:00:00 2001 From: Jiayuan Chen Date: Fri, 3 Apr 2026 09:45:12 +0800 Subject: [PATCH] net: skb: fix cross-cache free of KFENCE-allocated skb head SKB_SMALL_HEAD_CACHE_SIZE is intentionally set to a non-power-of-2 value (e.g. 704 on x86_64) to avoid collisions with generic kmalloc bucket sizes. This ensures that skb_kfree_head() can reliably use skb_end_offset to distinguish skb heads allocated from skb_small_head_cache vs. generic kmalloc caches. However, when KFENCE is enabled, kfence_ksize() returns the exact requested allocation size instead of the slab bucket size. If a caller (e.g. bpf_test_init) allocates skb head data via kzalloc() and the requested size happens to equal SKB_SMALL_HEAD_CACHE_SIZE, then slab_build_skb() -> ksize() returns that exact value. After subtracting skb_shared_info overhead, skb_end_offset ends up matching SKB_SMALL_HEAD_HEADROOM, causing skb_kfree_head() to incorrectly free the object to skb_small_head_cache instead of back to the original kmalloc cache, resulting in a slab cross-cache free: kmem_cache_free(skbuff_small_head): Wrong slab cache. Expected skbuff_small_head but got kmalloc-1k Fix this by always calling kfree(head) in skb_kfree_head(). This keeps the free path generic and avoids allocator-specific misclassification for KFENCE objects. Fixes: bf9f1baa279f ("net: add dedicated kmem_cache for typical/small skb->head") Reported-by: Antonius Closes: https://lore.kernel.org/netdev/CAK8a0jxC5L5N7hq-DT2_NhUyjBxrPocoiDazzsBk4TGgT1r4-A@mail.gmail.com/ Signed-off-by: Jiayuan Chen Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20260403014517.142550-1-jiayuan.chen@linux.dev Signed-off-by: Jakub Kicinski diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 0e217041958a..43ee86dcf2ea 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -1083,10 +1083,7 @@ static int skb_pp_frag_ref(struct sk_buff *skb) static void skb_kfree_head(void *head, unsigned int end_offset) { - if (end_offset == SKB_SMALL_HEAD_HEADROOM) - kmem_cache_free(net_hotdata.skb_small_head_cache, head); - else - kfree(head); + kfree(head); } static void skb_free_head(struct sk_buff *skb)