From: Waiman Long <longman@redhat.com>
To: Eric Biggers <ebiggers@kernel.org>
Cc: David Howells <dhowells@redhat.com>,
Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
James Morris <jmorris@namei.org>,
"Serge E. Hallyn" <serge@hallyn.com>,
Mimi Zohar <zohar@linux.ibm.com>,
keyrings@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-security-module@vger.kernel.org,
linux-integrity@vger.kernel.org,
Sumit Garg <sumit.garg@linaro.org>,
Jerry Snitselaar <jsnitsel@redhat.com>,
Roberto Sassu <roberto.sassu@huawei.com>,
Chris von Recklinghausen <crecklin@redhat.com>
Subject: Re: [PATCH] KEYS: Don't write out to userspace while holding key semaphore
Date: Thu, 5 Mar 2020 16:30:18 -0500 [thread overview]
Message-ID: <f581aab4-1bad-64b8-59bf-2da6c34c53c5@redhat.com> (raw)
In-Reply-To: <20200305211651.GA225345@gmail.com>
On 3/5/20 4:16 PM, Eric Biggers wrote:
> 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
>
That is true. Is there a limit of how much key data are expected to be
returned from the kernel? We could set an internal limit here on how
large the buffer can be.
Cheers,
Longman
next prev parent reply other threads:[~2020-03-05 21:30 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-05 21:06 [PATCH] KEYS: Don't write out to userspace while holding key semaphore Waiman Long
2020-03-05 21:16 ` Eric Biggers
2020-03-05 21:30 ` Waiman Long [this message]
2020-03-06 18:40 ` Jarkko Sakkinen
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