From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793209891; b=hFYAcHzghtxEhy+8mPb2Z8qKKJYu4fgAg5ZmgmccPubtgv18TPrKtkBZUxNLAOq9anFK tB/zGro3LSQMJA2FleJmYtqYKNUyVy+jb6ZhB5mEdD34bQC7gs3smQrif/IYaW8G9Sy1O 4+SiBKA+yhRNZEzqsxY+rtVy4sgVGMqGQqWuGdwxJk3d+rMw4sIG2+AlgEP/pLwmTcs1I k27b4RI6oI6vfddzJt3pQ6D/2umEy5tC6ymLivn9aXL8TIG/hIdW74MwlMjHGdWeTjtBp aYmTOALgnzQ8uz7MXN3KRpeLSbiPrmhRX4iYcmrxJS3u5qihLDnQXMh4SzV9DBLmgUA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793209891; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=APAMaIE6oZgbfBjXIPWVltHPbfCM+NdS0i2N20bREbg=; b=4Ji+riUgnBpza6DztKKRajsNfF23ABEgDHr+zCI84uze4aVXdt+xrO0KfIleiaRFV8eA sj7YR4XA7vGZ9cpx183pTY/WOETmVdu6aA3RuYhE1BmuhR04tXwiYJgd5x8lgCD2tbAJ5 XOcHhNBXp5kBeEjCKd6yuEFTR9UdWCGqi7S63Wj+t/RWzCNzXbxHAX5e9PhqV5BJeEsRR X6h3IT8dY0I9ol+Ta32QvxrgquIzK1MlA15dic24X13N5vQbBJbapI5js65IDnOZtwCJm Qsjuji85jylGuju3HTm5HHo4fYOwhYuMLdOa6Va42FPEyMPUAJIWCB7VGhDBwFqW5eg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=ofSaZo7D; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 82CD6606A31A; Wed, 28 Oct 2026 17:51:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=ofSaZo7D Received: by smtp.kernel.org (Postfix) with ESMTPSA id 862091F01825; Wed, 28 Oct 2026 17:51:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793209891; bh=APAMaIE6oZgbfBjXIPWVltHPbfCM+NdS0i2N20bREbg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ofSaZo7DhLi1M/byu03iEbErx5ozgc2g70Y2Sp5U8eC5BGjRIuBAyvhdFdLlC76ja kT2zJ39bzmt3ElSEeD8UeeqUu9af9PeQtpRPslC74VOH7ecEgMfxiTp8/EPJPg4zfE L2hvsEZTst9JycUHrNNPCj18LTWQtWqlcHyw6/xI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Cen Zhang , Jarkko Sakkinen Subject: [PATCH 6.18 093/109] keys: Protect the type name while describing a key Date: Wed, 28 Oct 2026 18:01:17 +0100 Message-ID: <20261028165944.543853060@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028165942.357251485@linuxfoundation.org> References: <20261028165942.357251485@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Cen Zhang commit fced7238b7e80cf8aa688d5af976e4aa6e33c329 upstream. keyctl_describe_key() must keep the key type's name alive until kasprintf() has consumed it. The retained key reference keeps the key and its description alive, but does not pin the module providing its type. The name is passed to kasprintf() without holding key->sem. kvasprintf() uses the saved name pointer in two formatting passes, with a GFP_KERNEL allocation between them. With AF_RXRPC=m, a task that passes View permission before type retirement can overlap a privileged module unload in this order: 1. KEYCTL_DESCRIBE looks up the key, saves key->type->name in the kasprintf() arguments and completes the first formatting pass. 2. While the formatter is delayed before its second pass, af_rxrpc_exit() calls unregister_key_type(), which removes the type from the registry and waits for key_gc_keytype(). 3. The collector takes key->sem for writing, retypes the retained key to key_type_dead and completes retirement. Unregistration and module exit return, allowing free_module() to release the type and name. 4. The formatter resumes its second pass and reads the saved name from released module storage, which can fault in string(). Hold key->sem for reading across kasprintf(). The collector then cannot retype the key or complete retirement until both formatting passes have finished. If retirement wins the lock first, formatting uses the core key_type_dead name instead. Release the semaphore immediately after kasprintf(), including on allocation failure, before copying to userspace. Oops report as below: BUG: unable to handle page fault for address: fffffbfff8054794 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page RIP: 0010:string+0x23f/0x470 Call Trace: vsnprintf+0x330/0x1110 Cc: stable@vger.kernel.org Fixes: aa9d4437893f ("KEYS: Fix the size of the key description passed to/from userspace") Assisted-by: LLM Signed-off-by: Cen Zhang Reviewed-by: Jarkko Sakkinen Link: https://lore.kernel.org/r/pm-key-management-objects-candidate-0009-v4-6b537c5732fd957c33fa@gmail.com Signed-off-by: Jarkko Sakkinen Signed-off-by: Greg Kroah-Hartman --- security/keys/keyctl.c | 2 ++ 1 file changed, 2 insertions(+) --- a/security/keys/keyctl.c +++ b/security/keys/keyctl.c @@ -677,12 +677,14 @@ okay: /* calculate how much information we're going to return */ ret = -ENOMEM; + down_read(&key->sem); infobuf = kasprintf(GFP_KERNEL, "%s;%d;%d;%08x;", key->type->name, from_kuid_munged(current_user_ns(), key->uid), from_kgid_munged(current_user_ns(), key->gid), key->perm); + up_read(&key->sem); if (!infobuf) goto error2; infolen = strlen(infobuf);