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authorIulia Manda <iulia.manda21@gmail.com>2015-04-15 16:16:41 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-04-15 16:35:22 -0700
commit2813893f8b197a14f1e1ddb04d99bce46817c84a (patch)
tree650651e638f867a6bda23e08c70bdd9857d121ca /include/linux/capability.h
parentc79574abe2baddf569532e7e430e4977771dd25c (diff)
kernel: conditionally support non-root users, groups and capabilities
There are a lot of embedded systems that run most or all of their functionality in init, running as root:root. For these systems, supporting multiple users is not necessary. This patch adds a new symbol, CONFIG_MULTIUSER, that makes support for non-root users, non-root groups, and capabilities optional. It is enabled under CONFIG_EXPERT menu. When this symbol is not defined, UID and GID are zero in any possible case and processes always have all capabilities. The following syscalls are compiled out: setuid, setregid, setgid, setreuid, setresuid, getresuid, setresgid, getresgid, setgroups, getgroups, setfsuid, setfsgid, capget, capset. Also, groups.c is compiled out completely. In kernel/capability.c, capable function was moved in order to avoid adding two ifdef blocks. This change saves about 25 KB on a defconfig build. The most minimal kernels have total text sizes in the high hundreds of kB rather than low MB. (The 25k goes down a bit with allnoconfig, but not that much. The kernel was booted in Qemu. All the common functionalities work. Adding users/groups is not possible, failing with -ENOSYS. Bloat-o-meter output: add/remove: 7/87 grow/shrink: 19/397 up/down: 1675/-26325 (-24650) [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Iulia Manda <iulia.manda21@gmail.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/capability.h')
-rw-r--r--include/linux/capability.h29
1 files changed, 29 insertions, 0 deletions
diff --git a/include/linux/capability.h b/include/linux/capability.h
index aa93e5ef594c..af9f0b9e80e6 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -205,6 +205,7 @@ static inline kernel_cap_t cap_raise_nfsd_set(const kernel_cap_t a,
cap_intersect(permitted, __cap_nfsd_set));
}
+#ifdef CONFIG_MULTIUSER
extern bool has_capability(struct task_struct *t, int cap);
extern bool has_ns_capability(struct task_struct *t,
struct user_namespace *ns, int cap);
@@ -213,6 +214,34 @@ extern bool has_ns_capability_noaudit(struct task_struct *t,
struct user_namespace *ns, int cap);
extern bool capable(int cap);
extern bool ns_capable(struct user_namespace *ns, int cap);
+#else
+static inline bool has_capability(struct task_struct *t, int cap)
+{
+ return true;
+}
+static inline bool has_ns_capability(struct task_struct *t,
+ struct user_namespace *ns, int cap)
+{
+ return true;
+}
+static inline bool has_capability_noaudit(struct task_struct *t, int cap)
+{
+ return true;
+}
+static inline bool has_ns_capability_noaudit(struct task_struct *t,
+ struct user_namespace *ns, int cap)
+{
+ return true;
+}
+static inline bool capable(int cap)
+{
+ return true;
+}
+static inline bool ns_capable(struct user_namespace *ns, int cap)
+{
+ return true;
+}
+#endif /* CONFIG_MULTIUSER */
extern bool capable_wrt_inode_uidgid(const struct inode *inode, int cap);
extern bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap);