1. 05 Sep, 2008 1 commit
    • Arjan van de Ven's avatar
      hrtimer: create a "timer_slack" field in the task struct · 6976675d
      Arjan van de Ven authored
      We want to be able to control the default "rounding" that is used by
      select() and poll() and friends. This is a per process property
      (so that we can have a "nice" like program to start certain programs with
      a looser or stricter rounding) that can be set/get via a prctl().
      For this purpose, a field called "timer_slack_ns" is added to the task
      struct. In addition, a field called "default_timer_slack"ns" is added
      so that tasks easily can temporarily to a more/less accurate slack and then
      back to the default.
      The default value of the slack is set to 50 usec; this is significantly less
      than 2.6.27's average select() and poll() timing error but still allows
      the kernel to group timers somewhat to preserve power behavior. Applications
      and admins can override this via the prctl()
      Signed-off-by: default avatarArjan van de Ven <arjan@linux.intel.com>
  2. 28 Apr, 2008 1 commit
    • Andrew G. Morgan's avatar
      capabilities: implement per-process securebits · 3898b1b4
      Andrew G. Morgan authored
      Filesystem capability support makes it possible to do away with (set)uid-0
      based privilege and use capabilities instead.  That is, with filesystem
      support for capabilities but without this present patch, it is (conceptually)
      possible to manage a system with capabilities alone and never need to obtain
      privilege via (set)uid-0.
      Of course, conceptually isn't quite the same as currently possible since few
      user applications, certainly not enough to run a viable system, are currently
      prepared to leverage capabilities to exercise privilege.  Further, many
      applications exist that may never get upgraded in this way, and the kernel
      will continue to want to support their setuid-0 base privilege needs.
      Where pure-capability applications evolve and replace setuid-0 binaries, it is
      desirable that there be a mechanisms by which they can contain their
      privilege.  In addition to leveraging the per-process bounding and inheritable
      sets, this should include suppressing the privilege of the uid-0 superuser
      from the process' tree of children.
      The feature added by this patch can be leveraged to suppress the privilege
      associated with (set)uid-0.  This suppression requires CAP_SETPCAP to
      initiate, and only immediately affects the 'current' process (it is inherited
      through fork()/exec()).  This reimplementation differs significantly from the
      historical support for securebits which was system-wide, unwieldy and which
      has ultimately withered to a dead relic in the source of the modern kernel.
      With this patch applied a process, that is capable(CAP_SETPCAP), can now drop
      all legacy privilege (through uid=0) for itself and all subsequently
      fork()'d/exec()'d children with:
        prctl(PR_SET_SECUREBITS, 0x2f);
      This patch represents a no-op unless CONFIG_SECURITY_FILE_CAPABILITIES is
      enabled at configure time.
      [akpm@linux-foundation.org: fix uninitialised var warning]
      [serue@us.ibm.com: capabilities: use cap_task_prctl when !CONFIG_SECURITY]
      Signed-off-by: default avatarAndrew G. Morgan <morgan@kernel.org>
      Acked-by: default avatarSerge Hallyn <serue@us.ibm.com>
      Reviewed-by: default avatarJames Morris <jmorris@namei.org>
      Cc: Stephen Smalley <sds@tycho.nsa.gov>
      Cc: Paul Moore <paul.moore@hp.com>
      Signed-off-by: default avatarSerge E. Hallyn <serue@us.ibm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  3. 19 Apr, 2008 1 commit
  4. 05 Feb, 2008 1 commit
    • Serge E. Hallyn's avatar
      capabilities: introduce per-process capability bounding set · 3b7391de
      Serge E. Hallyn authored
      The capability bounding set is a set beyond which capabilities cannot grow.
       Currently cap_bset is per-system.  It can be manipulated through sysctl,
      but only init can add capabilities.  Root can remove capabilities.  By
      default it includes all caps except CAP_SETPCAP.
      This patch makes the bounding set per-process when file capabilities are
      enabled.  It is inherited at fork from parent.  Noone can add elements,
      CAP_SETPCAP is required to remove them.
      One example use of this is to start a safer container.  For instance, until
      device namespaces or per-container device whitelists are introduced, it is
      best to take CAP_MKNOD away from a container.
      The bounding set will not affect pP and pE immediately.  It will only
      affect pP' and pE' after subsequent exec()s.  It also does not affect pI,
      and exec() does not constrain pI'.  So to really start a shell with no way
      of regain CAP_MKNOD, you would do
      	cap_t cap = cap_get_proc();
      	cap_value_t caparray[1];
      	caparray[0] = CAP_MKNOD;
      	cap_set_flag(cap, CAP_INHERITABLE, 1, caparray, CAP_DROP);
      The following test program will get and set the bounding
      set (but not pI).  For instance
      	./bset get
      		(lists capabilities in bset)
      	./bset drop cap_net_raw
      		(starts shell with new bset)
      		(use capset, setuid binary, or binary with
      		file capabilities to try to increase caps)
       #include <sys/prctl.h>
       #include <linux/capability.h>
       #include <sys/types.h>
       #include <unistd.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <string.h>
       #ifndef PR_CAPBSET_READ
       #define PR_CAPBSET_READ 23
       #ifndef PR_CAPBSET_DROP
       #define PR_CAPBSET_DROP 24
      int usage(char *me)
      	printf("Usage: %s get\n", me);
      	printf("       %s drop <capability>\n", me);
      	return 1;
       #define numcaps 32
      char *captable[numcaps] = {
      int getbcap(void)
      	int comma=0;
      	unsigned long i;
      	int ret;
      	printf("i know of %d capabilities\n", numcaps);
      	printf("capability bounding set:");
      	for (i=0; i<numcaps; i++) {
      		ret = prctl(PR_CAPBSET_READ, i);
      		if (ret < 0)
      		else if (ret==1)
      			printf("%s%s", (comma++) ? ", " : " ", captable[i]);
      	return 0;
      int capdrop(char *str)
      	unsigned long i;
      	int found=0;
      	for (i=0; i<numcaps; i++) {
      		if (strcmp(captable[i], str) == 0) {
      	if (!found)
      		return 1;
      	if (prctl(PR_CAPBSET_DROP, i)) {
      		return 1;
      	return 0;
      int main(int argc, char *argv[])
      	if (argc<2)
      		return usage(argv[0]);
      	if (strcmp(argv[1], "get")==0)
      		return getbcap();
      	if (strcmp(argv[1], "drop")!=0 || argc<3)
      		return usage(argv[0]);
      	if (capdrop(argv[2])) {
      		printf("unknown capability\n");
      		return 1;
      	return execl("/bin/bash", "/bin/bash", NULL);
      [serue@us.ibm.com: fix typo]
      Signed-off-by: default avatarSerge E. Hallyn <serue@us.ibm.com>
      Signed-off-by: default avatarAndrew G. Morgan <morgan@kernel.org>
      Cc: Stephen Smalley <sds@tycho.nsa.gov>
      Cc: James Morris <jmorris@namei.org>
      Cc: Chris Wright <chrisw@sous-sol.org>
      Cc: Casey Schaufler <casey@schaufler-ca.com>a
      Signed-off-by: default avatar"Serge E. Hallyn" <serue@us.ibm.com>
      Tested-by: default avatarJiri Slaby <jirislaby@gmail.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  5. 16 Jul, 2007 1 commit
  6. 09 Jun, 2006 1 commit
    • Anton Blanchard's avatar
      [PATCH] Add a prctl to change the endianness of a process. · 651d765d
      Anton Blanchard authored
      This new prctl is intended for changing the execution mode of the
      processor, on processors that support both a little-endian mode and a
      big-endian mode.  It is intended for use by programs such as
      instruction set emulators (for example an x86 emulator on PowerPC),
      which may find it convenient to use the processor in an alternate
      endianness mode when executing translated instructions.
      Note that this does not imply the existence of a fully-fledged ABI for
      both endiannesses, or of compatibility code for converting system
      calls done in the non-native endianness mode.  The program is expected
      to arrange for all of its system call arguments to be presented in the
      native endianness.
      Switching between big and little-endian mode will require some care in
      constructing the instruction sequence for the switch.  Generally the
      instructions up to the instruction that invokes the prctl system call
      will have to be in the old endianness, and subsequent instructions
      will have to be in the new endianness.
      Signed-off-by: default avatarAnton Blanchard <anton@samba.org>
      Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
  7. 16 Apr, 2005 1 commit
    • Linus Torvalds's avatar
      Linux-2.6.12-rc2 · 1da177e4
      Linus Torvalds authored
      Initial git repository build. I'm not bothering with the full history,
      even though we have it. We can create a separate "historical" git
      archive of that later if we want to, and in the meantime it's about
      3.2GB when imported into git - space that would just make the early
      git days unnecessarily complicated, when we don't have a lot of good
      infrastructure for it.
      Let it rip!