From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Biggers Date: Thu, 05 Mar 2020 21:16:51 +0000 Subject: Re: [PATCH] KEYS: Don't write out to userspace while holding key semaphore Message-Id: <20200305211651.GA225345@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit List-Id: References: <20200305210640.15315-1-longman@redhat.com> In-Reply-To: <20200305210640.15315-1-longman@redhat.com> To: Waiman Long Cc: David Howells , Jarkko Sakkinen , James Morris , "Serge E. Hallyn" , Mimi Zohar , keyrings@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-integrity@vger.kernel.org, Sumit Garg , Jerry Snitselaar , Roberto Sassu , Chris von Recklinghausen On Thu, Mar 05, 2020 at 04:06:40PM -0500, Waiman Long wrote: > diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c > index 9b898c969558..564a4d187329 100644 > --- a/security/keys/keyctl.c > +++ b/security/keys/keyctl.c > @@ -846,14 +846,36 @@ long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen) > can_read_key: > ret = -EOPNOTSUPP; > if (key->type->read) { > - /* Read the data with the semaphore held (since we might sleep) > + /* > + * Read the data with the semaphore held (since we might sleep) > * to protect against the key being updated or revoked. > + * > + * Allocating a temporary buffer to hold the keys before > + * transferring them to user buffer to avoid potential > + * deadlock involving page fault and mmap_sem. > */ > + char *tmpbuf = kmalloc(buflen, GFP_KERNEL); This is passing an arbitrarily large size from userspace into kmalloc(). - Eric