path: root/init
diff options
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 /init
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 'init')
1 files changed, 18 insertions, 1 deletions
diff --git a/init/Kconfig b/init/Kconfig
index a905b7301e10..3b9df1aa35db 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -394,6 +394,7 @@ endchoice
bool "BSD Process Accounting"
+ depends on MULTIUSER
If you say Y here, a user level program will be able to instruct the
kernel (via a special system call) to write process accounting
@@ -420,6 +421,7 @@ config BSD_PROCESS_ACCT_V3
bool "Export task/process statistics through netlink"
depends on NET
+ depends on MULTIUSER
default n
Export selected statistics for tasks/processes through the
@@ -1160,6 +1162,7 @@ config CHECKPOINT_RESTORE
menuconfig NAMESPACES
bool "Namespaces support" if EXPERT
+ depends on MULTIUSER
default !EXPERT
Provides the way to make tasks work with different objects using
@@ -1356,11 +1359,25 @@ menuconfig EXPERT
config UID16
bool "Enable 16-bit UID system calls" if EXPERT
- depends on HAVE_UID16
+ depends on HAVE_UID16 && MULTIUSER
default y
This enables the legacy 16-bit UID syscall wrappers.
+ bool "Multiple users, groups and capabilities support" if EXPERT
+ default y
+ help
+ This option enables support for non-root users, groups and
+ capabilities.
+ If you say N here, all processes will run with UID 0, GID 0, and all
+ possible capabilities. Saying N here also compiles out support for
+ system calls related to UIDs, GIDs, and capabilities, such as setuid,
+ setgid, and capset.
+ If unsure, say Y here.
bool "sgetmask/ssetmask syscalls support" if EXPERT
def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH

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