From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org (Eric W. Biederman) Subject: [REVIEW][PATCH 2/2] mnt: fs_fully_visible enforce noexec and nosuid if !SB_I_NOEXEC Date: Fri, 10 Jul 2015 11:18:17 -0500 Message-ID: <87bnfkyoja.fsf_-_@x220.int.ebiederm.org> References: <87381eyz26.fsf@x220.int.ebiederm.org> <87pp4eqktr.fsf@x220.int.ebiederm.org> <20150704231118.GT17109@ZenIV.linux.org.uk> <87mvz4yomp.fsf_-_@x220.int.ebiederm.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <87mvz4yomp.fsf_-_-JOvCrm2gF+uungPnsOpG7nhyD016LWXt@public.gmane.org> (Eric W. Biederman's message of "Fri, 10 Jul 2015 11:16:14 -0500") List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Linux Containers Cc: Seth Forshee , Linux API , Greg Kroah-Hartman , Al Viro , Andy Lutomirski , Kenton Varda , Michael Kerrisk-manpages , Richard Weinberger , linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Tejun Heo , Ivan Delalande , Linus Torvalds List-Id: linux-api@vger.kernel.org The filesystems proc and sysfs do not have executable files do not have exectuable files today and portions of userspace break if we do enforce nosuid and noexec consistency of nosuid and noexec flags between previous mounts and new mounts of proc and sysfs. Add the code to enforce consistency of the nosuid and noexec flags, and use the presence of SB_I_NOEXEC to signal that there is no need to bother. This results in a completely userspace invisible change that makes it clear fs_fully_visible can only skip the enforcement of noexec and nosuid because it is known the filesystems in question do not support executables. Signed-off-by: "Eric W. Biederman" --- fs/namespace.c | 33 +++++++++++++++++++++++++-------- 1 file changed, 25 insertions(+), 8 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index c7cb8a526c05..ce428cadd41f 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -3194,6 +3194,8 @@ static bool fs_fully_visible(struct file_system_type *type, int *new_mnt_flags) down_read(&namespace_sem); list_for_each_entry(mnt, &ns->list, mnt_list) { struct mount *child; + int mnt_flags; + if (mnt->mnt.mnt_sb->s_type != type) continue; @@ -3203,17 +3205,30 @@ static bool fs_fully_visible(struct file_system_type *type, int *new_mnt_flags) if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root) continue; + /* Read the mount flags and filter out flags that + * may safely be ignored. + */ + mnt_flags = mnt->mnt.mnt_flags; + if (mnt->mnt.mnt_sb->s_iflags & SB_I_NOEXEC) + mnt_flags &= ~(MNT_LOCK_NOSUID | MNT_LOCK_NOEXEC); + /* Verify the mount flags are equal to or more permissive * than the proposed new mount. */ - if ((mnt->mnt.mnt_flags & MNT_LOCK_READONLY) && + if ((mnt_flags & MNT_LOCK_READONLY) && !(new_flags & MNT_READONLY)) continue; - if ((mnt->mnt.mnt_flags & MNT_LOCK_NODEV) && + if ((mnt_flags & MNT_LOCK_NODEV) && !(new_flags & MNT_NODEV)) continue; - if ((mnt->mnt.mnt_flags & MNT_LOCK_ATIME) && - ((mnt->mnt.mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK))) + if ((mnt_flags & MNT_LOCK_NOSUID) && + !(new_flags & MNT_NOSUID)) + continue; + if ((mnt_flags & MNT_LOCK_NOEXEC) && + !(new_flags & MNT_NOEXEC)) + continue; + if ((mnt_flags & MNT_LOCK_ATIME) && + ((mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK))) continue; /* This mount is not fully visible if there are any @@ -3223,16 +3238,18 @@ static bool fs_fully_visible(struct file_system_type *type, int *new_mnt_flags) list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { struct inode *inode = child->mnt_mountpoint->d_inode; /* Only worry about locked mounts */ - if (!(mnt->mnt.mnt_flags & MNT_LOCKED)) + if (!(mnt_flags & MNT_LOCKED)) continue; /* Is the directory permanetly empty? */ if (!is_empty_dir_inode(inode)) goto next; } /* Preserve the locked attributes */ - *new_mnt_flags |= mnt->mnt.mnt_flags & (MNT_LOCK_READONLY | \ - MNT_LOCK_NODEV | \ - MNT_LOCK_ATIME); + *new_mnt_flags |= mnt_flags & (MNT_LOCK_READONLY | \ + MNT_LOCK_NODEV | \ + MNT_LOCK_NOSUID | \ + MNT_LOCK_NOEXEC | \ + MNT_LOCK_ATIME); visible = true; goto found; next: ; -- 2.2.1