From f84df2a6f268de584a201e8911384a2d244876e3 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Wed, 16 Nov 2016 22:06:51 -0600 Subject: exec: Ensure mm->user_ns contains the execed files When the user namespace support was merged the need to prevent ptrace from revealing the contents of an unreadable executable was overlooked. Correct this oversight by ensuring that the executed file or files are in mm->user_ns, by adjusting mm->user_ns. Use the new function privileged_wrt_inode_uidgid to see if the executable is a member of the user namespace, and as such if having CAP_SYS_PTRACE in the user namespace should allow tracing the executable. If not update mm->user_ns to the parent user namespace until an appropriate parent is found. Cc: stable@vger.kernel.org Reported-by: Jann Horn Fixes: 9e4a36ece652 ("userns: Fail exec for suid and sgid binaries with ids outside our user namespace.") Signed-off-by: "Eric W. Biederman" --- kernel/capability.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) (limited to 'kernel/capability.c') diff --git a/kernel/capability.c b/kernel/capability.c index dfa0e4528b0b..4984e1f552eb 100644 --- a/kernel/capability.c +++ b/kernel/capability.c @@ -456,6 +456,19 @@ bool file_ns_capable(const struct file *file, struct user_namespace *ns, } EXPORT_SYMBOL(file_ns_capable); +/** + * privileged_wrt_inode_uidgid - Do capabilities in the namespace work over the inode? + * @ns: The user namespace in question + * @inode: The inode in question + * + * Return true if the inode uid and gid are within the namespace. + */ +bool privileged_wrt_inode_uidgid(struct user_namespace *ns, const struct inode *inode) +{ + return kuid_has_mapping(ns, inode->i_uid) && + kgid_has_mapping(ns, inode->i_gid); +} + /** * capable_wrt_inode_uidgid - Check nsown_capable and uid and gid mapped * @inode: The inode in question @@ -469,8 +482,7 @@ bool capable_wrt_inode_uidgid(const struct inode *inode, int cap) { struct user_namespace *ns = current_user_ns(); - return ns_capable(ns, cap) && kuid_has_mapping(ns, inode->i_uid) && - kgid_has_mapping(ns, inode->i_gid); + return ns_capable(ns, cap) && privileged_wrt_inode_uidgid(ns, inode); } EXPORT_SYMBOL(capable_wrt_inode_uidgid); -- cgit v1.2.3-58-ga151