From: Casey Schaufler <casey@schaufler-ca.com>
To: Eric Biggers <ebiggers@kernel.org>,
linux-security-module@vger.kernel.org,
James Morris <jmorris@namei.org>,
"Serge E . Hallyn" <serge@hallyn.com>
Cc: syzkaller-bugs@googlegroups.com, linux-kernel@vger.kernel.org,
stable@vger.kernel.org,
syzbot+e6416dabb497a650da40@syzkaller.appspotmail.com,
Casey Schaufler <casey@schaufler-ca.com>
Subject: Re: [PATCH] Smack: fix use-after-free in smk_write_relabel_self()
Date: Mon, 20 Jul 2020 17:57:03 -0700 [thread overview]
Message-ID: <4b7b9cbc-2c8d-0582-67f4-a8b095b78959@schaufler-ca.com> (raw)
In-Reply-To: <20200721003830.GC7464@sol.localdomain>
On 7/20/2020 5:38 PM, Eric Biggers wrote:
> On Wed, Jul 08, 2020 at 01:15:20PM -0700, Eric Biggers wrote:
>> From: Eric Biggers <ebiggers@google.com>
>>
>> smk_write_relabel_self() frees memory from the task's credentials with
>> no locking, which can easily cause a use-after-free because multiple
>> tasks can share the same credentials structure.
>>
>> Fix this by using prepare_creds() and commit_creds() to correctly modify
>> the task's credentials.
>>
>> Reproducer for "BUG: KASAN: use-after-free in smk_write_relabel_self":
>>
>> #include <fcntl.h>
>> #include <pthread.h>
>> #include <unistd.h>
>>
>> static void *thrproc(void *arg)
>> {
>> int fd = open("/sys/fs/smackfs/relabel-self", O_WRONLY);
>> for (;;) write(fd, "foo", 3);
>> }
>>
>> int main()
>> {
>> pthread_t t;
>> pthread_create(&t, NULL, thrproc, NULL);
>> thrproc(NULL);
>> }
>>
>> Reported-by: syzbot+e6416dabb497a650da40@syzkaller.appspotmail.com
>> Fixes: 38416e53936e ("Smack: limited capability for changing process label")
>> Cc: <stable@vger.kernel.org> # v4.4+
>> Signed-off-by: Eric Biggers <ebiggers@google.com>
> Ping.
I have queued your patch and will be pushing it for next shortly.
prev parent reply other threads:[~2020-07-21 0:57 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-08 21:56 KASAN: use-after-free Read in smk_write_relabel_self syzbot
2020-07-08 20:15 ` [PATCH] Smack: fix use-after-free in smk_write_relabel_self() Eric Biggers
2020-07-16 0:27 ` Sasha Levin
2020-07-21 0:38 ` Eric Biggers
2020-07-21 0:57 ` Casey Schaufler [this message]
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