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| author | Iulia Manda <iulia.manda21@gmail.com> | 2015-04-15 16:16:41 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-04-15 16:35:22 -0700 |
| commit | 2813893f8b197a14f1e1ddb04d99bce46817c84a (patch) | |
| tree | 650651e638f867a6bda23e08c70bdd9857d121ca /kernel/cred.c | |
| parent | c79574abe2baddf569532e7e430e4977771dd25c (diff) | |
| download | linux-2813893f8b197a14f1e1ddb04d99bce46817c84a.tar.gz linux-2813893f8b197a14f1e1ddb04d99bce46817c84a.tar.xz | |
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 'kernel/cred.c')
| -rw-r--r-- | kernel/cred.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/cred.c b/kernel/cred.c index e0573a43c7df..ec1c07667ec1 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -29,6 +29,9 @@ static struct kmem_cache *cred_jar; +/* init to 2 - one for init_task, one to ensure it is never freed */ +struct group_info init_groups = { .usage = ATOMIC_INIT(2) }; + /* * The initial credentials for the initial task */ |