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authorEric W. Biederman <ebiederm@xmission.com>2014-12-02 12:27:26 -0600
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-01-08 09:58:16 -0800
commit1c587ee50ec44a2cf07cd160c214a683608b4d2c (patch)
treeb6259344d064228a86830ae99a9c36fc89b71fca /include/linux
parent6eaab78729f4e689a86ce6bc4e33453ebff9625d (diff)
userns: Add a knob to disable setgroups on a per user namespace basis
commit 9cc46516ddf497ea16e8d7cb986ae03a0f6b92f8 upstream. - Expose the knob to user space through a proc file /proc/<pid>/setgroups A value of "deny" means the setgroups system call is disabled in the current processes user namespace and can not be enabled in the future in this user namespace. A value of "allow" means the segtoups system call is enabled. - Descendant user namespaces inherit the value of setgroups from their parents. - A proc file is used (instead of a sysctl) as sysctls currently do not allow checking the permissions at open time. - Writing to the proc file is restricted to before the gid_map for the user namespace is set. This ensures that disabling setgroups at a user namespace level will never remove the ability to call setgroups from a process that already has that ability. A process may opt in to the setgroups disable for itself by creating, entering and configuring a user namespace or by calling setns on an existing user namespace with setgroups disabled. Processes without privileges already can not call setgroups so this is a noop. Prodcess with privilege become processes without privilege when entering a user namespace and as with any other path to dropping privilege they would not have the ability to call setgroups. So this remains within the bounds of what is possible without a knob to disable setgroups permanently in a user namespace. Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/user_namespace.h7
1 files changed, 7 insertions, 0 deletions
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 648cf88c5d6d..a37081cf59da 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -17,6 +17,10 @@ struct uid_gid_map { /* 64 bytes -- 1 cache line */
} extent[UID_GID_MAP_MAX_EXTENTS];
};
+#define USERNS_SETGROUPS_ALLOWED 1UL
+
+#define USERNS_INIT_FLAGS USERNS_SETGROUPS_ALLOWED
+
struct user_namespace {
struct uid_gid_map uid_map;
struct uid_gid_map gid_map;
@@ -27,6 +31,7 @@ struct user_namespace {
kuid_t owner;
kgid_t group;
unsigned int proc_inum;
+ unsigned long flags;
bool may_mount_sysfs;
bool may_mount_proc;
};
@@ -59,6 +64,8 @@ extern struct seq_operations proc_projid_seq_operations;
extern ssize_t proc_uid_map_write(struct file *, const char __user *, size_t, loff_t *);
extern ssize_t proc_gid_map_write(struct file *, const char __user *, size_t, loff_t *);
extern ssize_t proc_projid_map_write(struct file *, const char __user *, size_t, loff_t *);
+extern ssize_t proc_setgroups_write(struct file *, const char __user *, size_t, loff_t *);
+extern int proc_setgroups_show(struct seq_file *m, void *v);
extern bool userns_may_setgroups(const struct user_namespace *ns);
#else