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 5F4D53E8C50; Tue, 31 Mar 2026 16:50:16 +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=1774975816; cv=none; b=CSsvWqRxyevQfo1YazRdz7iUPoGexXdeg1Bg90cMbtjFHpdz5Y6IgLi/LO0IlLSXCVZS4to/bklYXvQCke0/MSNe2jJW3cP/nbAtxwY4PtsgPipBXBCxXRKR0epluniznbrNtgFdKQgV2NQccbiaxwlsBCMkggRBiHcgbkdCHYg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774975816; c=relaxed/simple; bh=Z0VkR3/1egvW2hGgD/GeIwvL6PfeCQd8uwnR7ugnksE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=q75aaJzHZNoCE5Y227oPGE0eNwCj0Abccj5lUt4NDUCCmjs+M35WSs7GUXY241lT++rAaa3z3NNZ/5RP5B7rCEOrMrN+O6NpN4mLa/NyaTfcW27lMWTMNAcQRWnz+VgSw1IHwzEEVURBgyb6RoCm5QTJGLXKqffsAEmAzSvoSE0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=d7eDtUvG; 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="d7eDtUvG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EC130C19423; Tue, 31 Mar 2026 16:50:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1774975816; bh=Z0VkR3/1egvW2hGgD/GeIwvL6PfeCQd8uwnR7ugnksE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=d7eDtUvGBSmFFCrS5hv5MUAx5goZUd8+TtQetvDe4reqHJ3tdg8MYLEmCNSpGQrrO oV8TIkEX8VaG0kFIRyNenx372vrkrOa9OfsovWAgKRW+OnNlrYHATnw0cQeL5NY4Z9 u22FChYOsW6ZpBbJcjsH/z6auGfmJxLtacK3kcDc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Qi Tang , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.12 070/244] net/smc: fix double-free of smc_spd_priv when tee() duplicates splice pipe buffer Date: Tue, 31 Mar 2026 18:20:20 +0200 Message-ID: <20260331161744.273123544@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260331161741.651718120@linuxfoundation.org> References: <20260331161741.651718120@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Qi Tang [ Upstream commit 24dd586bb4cbba1889a50abe74143817a095c1c9 ] smc_rx_splice() allocates one smc_spd_priv per pipe_buffer and stores the pointer in pipe_buffer.private. The pipe_buf_operations for these buffers used .get = generic_pipe_buf_get, which only increments the page reference count when tee(2) duplicates a pipe buffer. The smc_spd_priv pointer itself was not handled, so after tee() both the original and the cloned pipe_buffer share the same smc_spd_priv *. When both pipes are subsequently released, smc_rx_pipe_buf_release() is called twice against the same object: 1st call: kfree(priv) sock_put(sk) smc_rx_update_cons() [correct] 2nd call: kfree(priv) sock_put(sk) smc_rx_update_cons() [UAF] KASAN reports a slab-use-after-free in smc_rx_pipe_buf_release(), which then escalates to a NULL-pointer dereference and kernel panic via smc_rx_update_consumer() when it chases the freed priv->smc pointer: BUG: KASAN: slab-use-after-free in smc_rx_pipe_buf_release+0x78/0x2a0 Read of size 8 at addr ffff888004a45740 by task smc_splice_tee_/74 Call Trace: dump_stack_lvl+0x53/0x70 print_report+0xce/0x650 kasan_report+0xc6/0x100 smc_rx_pipe_buf_release+0x78/0x2a0 free_pipe_info+0xd4/0x130 pipe_release+0x142/0x160 __fput+0x1c6/0x490 __x64_sys_close+0x4f/0x90 do_syscall_64+0xa6/0x1a0 entry_SYSCALL_64_after_hwframe+0x77/0x7f BUG: kernel NULL pointer dereference, address: 0000000000000020 RIP: 0010:smc_rx_update_consumer+0x8d/0x350 Call Trace: smc_rx_pipe_buf_release+0x121/0x2a0 free_pipe_info+0xd4/0x130 pipe_release+0x142/0x160 __fput+0x1c6/0x490 __x64_sys_close+0x4f/0x90 do_syscall_64+0xa6/0x1a0 entry_SYSCALL_64_after_hwframe+0x77/0x7f Kernel panic - not syncing: Fatal exception Beyond the memory-safety problem, duplicating an SMC splice buffer is semantically questionable: smc_rx_update_cons() would advance the consumer cursor twice for the same data, corrupting receive-window accounting. A refcount on smc_spd_priv could fix the double-free, but the cursor-accounting issue would still need to be addressed separately. The .get callback is invoked by both tee(2) and splice_pipe_to_pipe() for partial transfers; both will now return -EFAULT. Users who need to duplicate SMC socket data must use a copy-based read path. Fixes: 9014db202cb7 ("smc: add support for splice()") Signed-off-by: Qi Tang Link: https://patch.msgid.link/20260318064847.23341-1-tpluszz77@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/smc/smc_rx.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/net/smc/smc_rx.c b/net/smc/smc_rx.c index 79047721df511..e7a6c2602e786 100644 --- a/net/smc/smc_rx.c +++ b/net/smc/smc_rx.c @@ -135,9 +135,16 @@ static void smc_rx_pipe_buf_release(struct pipe_inode_info *pipe, sock_put(sk); } +static bool smc_rx_pipe_buf_get(struct pipe_inode_info *pipe, + struct pipe_buffer *buf) +{ + /* smc_spd_priv in buf->private is not shareable; disallow cloning. */ + return false; +} + static const struct pipe_buf_operations smc_pipe_ops = { .release = smc_rx_pipe_buf_release, - .get = generic_pipe_buf_get + .get = smc_rx_pipe_buf_get, }; static void smc_rx_spd_release(struct splice_pipe_desc *spd, -- 2.51.0