From: ebiederm@xmission.com (Eric W. Biederman)
To: Ilya Matveychikov <matvejchikov@gmail.com>
Cc: linux-kernel@vger.kernel.org,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH] ksys_mount: check for permissions before resource allocation
Date: Tue, 05 Jun 2018 14:56:31 -0500 [thread overview]
Message-ID: <87o9gpatxs.fsf@xmission.com> (raw)
In-Reply-To: <BD48252B-65D7-4238-BDA2-71BAC1CEA855@gmail.com> (Ilya Matveychikov's message of "Tue, 5 Jun 2018 10:59:51 +0400")
Ilya Matveychikov <matvejchikov@gmail.com> writes:
> Just CC’ed to some of maintainers.
>
> $ perl scripts/get_maintainer.pl fs/0001-ksys_mount-check-for-permissions-before-resource-all.patch
> Alexander Viro <viro@zeniv.linux.org.uk> (maintainer:FILESYSTEMS (VFS and infrastructure))
> linux-fsdevel@vger.kernel.org (open list:FILESYSTEMS (VFS and infrastructure))
> linux-kernel@vger.kernel.org (open list)
>
>> On Jun 5, 2018, at 6:00 AM, Ilya Matveychikov <matvejchikov@gmail.com> wrote:
>>
>> Early check for mount permissions prevents possible allocation of 3
>> pages from kmalloc() pool by unpriveledged user which can be used for
>> spraying the kernel heap.
*Snort*
You clearly have not read may_mount. Your modified code still
let's unprivileged users in. So even if all of Al's good objections
were not applicable this change would still be buggy and wrong.
Nacked-by: "Eric W. Biederman" <ebiederm@xmission.com>
>> Signed-off-by: Ilya V. Matveychikov <matvejchikov@gmail.com>
>> ---
>> fs/namespace.c | 3 +++
>> 1 file changed, 3 insertions(+)
>>
>> diff --git a/fs/namespace.c b/fs/namespace.c
>> index 5f75969adff1..1ef8feb2de2a 100644
>> --- a/fs/namespace.c
>> +++ b/fs/namespace.c
>> @@ -3046,6 +3046,9 @@ int ksys_mount(char __user *dev_name, char __user *dir_name, char __user *type,
>> char *kernel_dev;
>> void *options;
>>
>> + if (!may_mount())
>> + return -EPERM;
>> +
>> kernel_type = copy_mount_string(type);
>> ret = PTR_ERR(kernel_type);
>> if (IS_ERR(kernel_type))
>> --
>> 2.17.0
>>
next prev parent reply other threads:[~2018-06-05 19:56 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <D2317950-0DB0-4311-ADB1-FF677B676E04@gmail.com>
2018-06-05 6:59 ` [PATCH] ksys_mount: check for permissions before resource allocation Ilya Matveychikov
2018-06-05 11:26 ` Al Viro
2018-06-05 11:35 ` Ilya Matveychikov
2018-06-05 11:53 ` Al Viro
2018-06-05 12:07 ` Ilya Matveychikov
2018-06-05 12:28 ` David Sterba
2018-06-05 12:42 ` Ilya Matveychikov
2018-06-05 12:34 ` Al Viro
2018-06-05 19:56 ` Eric W. Biederman [this message]
2018-06-06 9:32 ` Ilya Matveychikov
2018-06-06 14:22 ` Eric W. Biederman
2018-06-06 15:26 ` Ilya Matveychikov
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