Hello Zefan Li,
I'm really not sure but this patch might be needed for 3.4 too.
Thanks
On 09/03/2014 06:15 PM, Francis Moreau wrote:
> Hello,
>
> Is it also needed by 3.2.x and 3.4.x ?
>
> Thanks
>
> On 08/25/2014 06:54 PM, Kamal Mostafa wrote:
>> 3.8.13.28 -stable review patch. If anyone has any objections, please let me know.
>>
>> ------------------
>>
>> From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
>>
>> commit a6138db815df5ee542d848318e5dae681590fccd upstream.
>>
>> Kenton Varda <kenton@xxxxxxxxxxxx> discovered that by remounting a
>> read-only bind mount read-only in a user namespace the
>> MNT_LOCK_READONLY bit would be cleared, allowing an unprivileged user
>> to the remount a read-only mount read-write.
>>
>> Correct this by replacing the mask of mount flags to preserve
>> with a mask of mount flags that may be changed, and preserve
>> all others. This ensures that any future bugs with this mask and
>> remount will fail in an easy to detect way where new mount flags
>> simply won't change.
>>
>> Acked-by: Serge E. Hallyn <serge.hallyn@xxxxxxxxxx>
>> Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
>> Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
>> ---
>> fs/namespace.c | 2 +-
>> include/linux/mount.h | 4 +++-
>> 2 files changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/namespace.c b/fs/namespace.c
>> index 5dd7709..ddbd5bc 100644
>> --- a/fs/namespace.c
>> +++ b/fs/namespace.c
>> @@ -1782,7 +1782,7 @@ static int do_remount(struct path *path, int flags, int mnt_flags,
>> err = do_remount_sb(sb, flags, data, 0);
>> if (!err) {
>> br_write_lock(&vfsmount_lock);
>> - mnt_flags |= mnt->mnt.mnt_flags & MNT_PROPAGATION_MASK;
>> + mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK;
>> mnt->mnt.mnt_flags = mnt_flags;
>> br_write_unlock(&vfsmount_lock);
>> }
>> diff --git a/include/linux/mount.h b/include/linux/mount.h
>> index 73005f9..16fc05d 100644
>> --- a/include/linux/mount.h
>> +++ b/include/linux/mount.h
>> @@ -42,7 +42,9 @@ struct mnt_namespace;
>> * flag, consider how it interacts with shared mounts.
>> */
>> #define MNT_SHARED_MASK (MNT_UNBINDABLE)
>> -#define MNT_PROPAGATION_MASK (MNT_SHARED | MNT_UNBINDABLE)
>> +#define MNT_USER_SETTABLE_MASK (MNT_NOSUID | MNT_NODEV | MNT_NOEXEC \
>> + | MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME \
>> + | MNT_READONLY)
>>
>>
>> #define MNT_INTERNAL 0x4000
>>
>
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