[lkml]   [2018]   [Oct]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH 31/34] vfs: syscall: Add fspick() to select a superblock for reconfiguration [ver #12]
On 13/10/2018 07:11, Al Viro wrote:
> On Fri, Oct 12, 2018 at 03:49:50PM +0100, Alan Jenkins wrote:
>>> +SYSCALL_DEFINE3(fspick, int, dfd, const char __user *, path, unsigned int, flags)
>>> +{
>>> + struct fs_context *fc;
>>> + struct path target;
>>> + unsigned int lookup_flags;
>>> + int ret;
>>> +
>>> + if (!ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN))
>>> + return -EPERM;
>> This seems to accept basically any mount.  Specifically: are you sure it's
>> OK to return a handle to a SB_NO_USER superblock?
> Umm... As long as we don't try to do pathname resolution from its ->s_root,
> shouldn't be a problem and I don't see anything that would do that. I might've
> missed something, but...

Sorry, I guess SB_NOUSER was the wrong word.  I was trying find if
anything stopped things like

int memfd = memfd_create("foo", 0);
int fsfd = fspick(memfd, "", FSPICK_EMPTY_PATH);

fsconfig(fsfd, FSCONFIG_SET_FLAG, "ro", NULL, 0);
fsconfig(fsfd, FSCONFIG_SET_STRING, "size", "100M", 0);

So far I'm getting -EBUSY if I try to apply the "ro", -EINVAL if I try
to apply the "size=100M".  But if I don't apply either, then

It seems worrying that it might let me set options on shm_mnt. Or at
least letting me get as far as the -EBUSY check for the "ro" superblock

I'm not sure why I'm getting the -EINVAL setting the "size" option.  But
it would be much more reassuring if I was getting -EPERM :-).


 \ /
  Last update: 2018-10-13 11:46    [W:0.197 / U:0.904 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site