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author | Seth Forshee <seth.forshee@canonical.com> | 2015-09-23 22:16:04 +0200 |
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committer | Eric W. Biederman <ebiederm@xmission.com> | 2016-06-24 17:40:31 +0200 |
commit | d07b846f6200454c50d791796edb82660192513d (patch) | |
tree | 0addc4233c4e08fc7ca69511761bbd2c7402c1de /kernel | |
parent | userns: Remove the now unnecessary FS_USERNS_DEV_MOUNT flag (diff) | |
download | linux-d07b846f6200454c50d791796edb82660192513d.tar.xz linux-d07b846f6200454c50d791796edb82660192513d.zip |
fs: Limit file caps to the user namespace of the super block
Capability sets attached to files must be ignored except in the
user namespaces where the mounter is privileged, i.e. s_user_ns
and its descendants. Otherwise a vector exists for gaining
privileges in namespaces where a user is not already privileged.
Add a new helper function, current_in_user_ns(), to test whether a user
namespace is the same as or a descendant of another namespace.
Use this helper to determine whether a file's capability set
should be applied to the caps constructed during exec.
--EWB Replaced in_userns with the simpler current_in_userns.
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/user_namespace.c | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 9bafc211930c..68f594212759 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -938,6 +938,20 @@ bool userns_may_setgroups(const struct user_namespace *ns) return allowed; } +/* + * Returns true if @ns is the same namespace as or a descendant of + * @target_ns. + */ +bool current_in_userns(const struct user_namespace *target_ns) +{ + struct user_namespace *ns; + for (ns = current_user_ns(); ns; ns = ns->parent) { + if (ns == target_ns) + return true; + } + return false; +} + static inline struct user_namespace *to_user_ns(struct ns_common *ns) { return container_of(ns, struct user_namespace, ns); |