diff options
| 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 /init/Kconfig | |
| parent | c79574abe2baddf569532e7e430e4977771dd25c (diff) | |
| download | lwn-2813893f8b197a14f1e1ddb04d99bce46817c84a.tar.gz lwn-2813893f8b197a14f1e1ddb04d99bce46817c84a.zip | |
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/Kconfig')
| -rw-r--r-- | init/Kconfig | 19 |
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 config BSD_PROCESS_ACCT bool "BSD Process Accounting" + depends on MULTIUSER help 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 config TASKSTATS bool "Export task/process statistics through netlink" depends on NET + depends on MULTIUSER default n help 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 help 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 help This enables the legacy 16-bit UID syscall wrappers. +config MULTIUSER + 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. + config SGETMASK_SYSCALL bool "sgetmask/ssetmask syscalls support" if EXPERT def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH |