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| author | Eric W. Biederman <ebiederm@xmission.com> | 2013-04-14 22:47:02 +0200 |
|---|---|---|
| committer | Andy Lutomirski <luto@amacapital.net> | 2013-04-15 03:11:14 +0200 |
| commit | 6708075f104c3c9b04b23336bb0366ca30c3931b (patch) | |
| tree | 4e99cf865cea3d809bfadda9eec45dcf29454bee /kernel/user_namespace.c | |
| parent | Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/ker... (diff) | |
| download | linux-6708075f104c3c9b04b23336bb0366ca30c3931b.tar.xz linux-6708075f104c3c9b04b23336bb0366ca30c3931b.zip | |
userns: Don't let unprivileged users trick privileged users into setting the id_map
When we require privilege for setting /proc/<pid>/uid_map or
/proc/<pid>/gid_map no longer allow an unprivileged user to
open the file and pass it to a privileged program to write
to the file.
Instead when privilege is required require both the opener and the
writer to have the necessary capabilities.
I have tested this code and verified that setting /proc/<pid>/uid_map
fails when an unprivileged user opens the file and a privielged user
attempts to set the mapping, that unprivileged users can still map
their own id, and that a privileged users can still setup an arbitrary
mapping.
Reported-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Diffstat (limited to 'kernel/user_namespace.c')
| -rw-r--r-- | kernel/user_namespace.c | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index a54f26f82eb2..e2d4ace4481b 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -25,7 +25,8 @@ static struct kmem_cache *user_ns_cachep __read_mostly; -static bool new_idmap_permitted(struct user_namespace *ns, int cap_setid, +static bool new_idmap_permitted(const struct file *file, + struct user_namespace *ns, int cap_setid, struct uid_gid_map *map); static void set_cred_user_ns(struct cred *cred, struct user_namespace *user_ns) @@ -700,7 +701,7 @@ static ssize_t map_write(struct file *file, const char __user *buf, ret = -EPERM; /* Validate the user is allowed to use user id's mapped to. */ - if (!new_idmap_permitted(ns, cap_setid, &new_map)) + if (!new_idmap_permitted(file, ns, cap_setid, &new_map)) goto out; /* Map the lower ids from the parent user namespace to the @@ -787,7 +788,8 @@ ssize_t proc_projid_map_write(struct file *file, const char __user *buf, size_t &ns->projid_map, &ns->parent->projid_map); } -static bool new_idmap_permitted(struct user_namespace *ns, int cap_setid, +static bool new_idmap_permitted(const struct file *file, + struct user_namespace *ns, int cap_setid, struct uid_gid_map *new_map) { /* Allow mapping to your own filesystem ids */ @@ -811,8 +813,10 @@ static bool new_idmap_permitted(struct user_namespace *ns, int cap_setid, /* Allow the specified ids if we have the appropriate capability * (CAP_SETUID or CAP_SETGID) over the parent user namespace. + * And the opener of the id file also had the approprpiate capability. */ - if (ns_capable(ns->parent, cap_setid)) + if (ns_capable(ns->parent, cap_setid) && + file_ns_capable(file, ns->parent, cap_setid)) return true; return false; |