Documented the currently bogus state of support for CFS user groups with
user namespaces. In particular, all users in a user namespace should be
children of the user which created the user namespace. This is yet to
be implemented.
Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Acked-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
While ideally CLONE_NEWUSER will eventually require no
privilege, the required permission checks are currently
not there. As a result, CLONE_NEWUSER has the same effect
as a setuid(0)+setgroups(1,"0"). While we already require
CAP_SYS_ADMIN, requiring CAP_SETUID and CAP_SETGID seems
appropriate.
Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: James Morris <jmorris@namei.org>
(These two patches are in the next-unacked branch of
git://git.kernel.org/pub/scm/linux/kernel/git/sergeh/userns-2.6.
If they get some ACKs, then I hope to feed this into security-next.
After these two, I think we're ready to tackle userns+capabilities)
Fairsched creates a per-uid directory under /sys/kernel/uids/.
So when you clone(CLONE_NEWUSER), it tries to create
/sys/kernel/uids/0, which already exists, and you get back
-ENOMEM.
This was supposed to be fixed by sysfs tagging, but that
was postponed (ok, rejected until sysfs locking is fixed).
So, just as with network namespaces, we just don't create
those directories for user namespaces other than the init.
Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
Conflicts:
fs/nfsd/nfs4recover.c
Manually fixed above to use new creds API functions, e.g.
nfs4_save_creds().
Signed-off-by: James Morris <jmorris@namei.org>
It has been thought that the per-user file descriptors limit would also
limit the resources that a normal user can request via the epoll
interface. Vegard Nossum reported a very simple program (a modified
version attached) that can make a normal user to request a pretty large
amount of kernel memory, well within the its maximum number of fds. To
solve such problem, default limits are now imposed, and /proc based
configuration has been introduced. A new directory has been created,
named /proc/sys/fs/epoll/ and inside there, there are two configuration
points:
max_user_instances = Maximum number of devices - per user
max_user_watches = Maximum number of "watched" fds - per user
The current default for "max_user_watches" limits the memory used by epoll
to store "watches", to 1/32 of the amount of the low RAM. As example, a
256MB 32bit machine, will have "max_user_watches" set to roughly 90000.
That should be enough to not break existing heavy epoll users. The
default value for "max_user_instances" is set to 128, that should be
enough too.
This also changes the userspace, because a new error code can now come out
from EPOLL_CTL_ADD (-ENOSPC). The EMFILE from epoll_create() was already
listed, so that should be ok.
[akpm@linux-foundation.org: use get_current_user()]
Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: <stable@kernel.org>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Reported-by: Vegard Nossum <vegardno@ifi.uio.no>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
sched: prevent divide by zero error in cpu_avg_load_per_task, update
sched, cpusets: fix warning in kernel/cpuset.c
sched: prevent divide by zero error in cpu_avg_load_per_task
* 'irq-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
irq.h: fix missing/extra kernel-doc
genirq: __irq_set_trigger: change pr_warning to pr_debug
irq: fix typo
x86: apic honour irq affinity which was set in early boot
genirq: fix the affinity setting in setup_irq
genirq: keep affinities set from userspace across free/request_irq()
All architectures now use the generic compat_sys_ptrace, as should every
new architecture that needs 32bit compat (if we'll ever get another).
Remove the now superflous __ARCH_WANT_COMPAT_SYS_PTRACE define, and also
kill a comment about __ARCH_SYS_PTRACE that was added after
__ARCH_SYS_PTRACE was already gone.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Regarding the bug addressed in:
4cd4262: sched: prevent divide by zero error in cpu_avg_load_per_task
Linus points out that the fix is not complete:
> There's nothing that keeps gcc from deciding not to reload
> rq->nr_running.
>
> Of course, in _practice_, I don't think gcc ever will (if it decides
> that it will spill, gcc is likely going to decide that it will
> literally spill the local variable to the stack rather than decide to
> reload off the pointer), but it's a valid compiler optimization, and
> it even has a name (rematerialization).
>
> So I suspect that your patch does fix the bug, but it still leaves the
> fairly unlikely _potential_ for it to re-appear at some point.
>
> We have ACCESS_ONCE() as a macro to guarantee that the compiler
> doesn't rematerialize a pointer access. That also would clarify
> the fact that we access something unsafe outside a lock.
So make sure our nr_running value is immutable and cannot change
after we check it for nonzero.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
this warning:
kernel/cpuset.c: In function ‘generate_sched_domains’:
kernel/cpuset.c:588: warning: ‘ndoms’ may be used uninitialized in this function
triggers because GCC does not recognize that ndoms stays uninitialized
only if doms is NULL - but that flow is covered at the end of
generate_sched_domains().
Help out GCC by initializing this variable to 0. (that's prudent anyway)
Also, this function needs a splitup and code flow simplification:
with 160 lines length it's clearly too long.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: fix divide by zero crash in scheduler rebalance irq
While testing the branch profiler, I hit this crash:
divide error: 0000 [#1] PREEMPT SMP
[...]
RIP: 0010:[<ffffffff8024a008>] [<ffffffff8024a008>] cpu_avg_load_per_task+0x50/0x7f
[...]
Call Trace:
<IRQ> <0> [<ffffffff8024fd43>] find_busiest_group+0x3e5/0xcaa
[<ffffffff8025da75>] rebalance_domains+0x2da/0xa21
[<ffffffff80478769>] ? find_next_bit+0x1b2/0x1e6
[<ffffffff8025e2ce>] run_rebalance_domains+0x112/0x19f
[<ffffffff8026d7c2>] __do_softirq+0xa8/0x232
[<ffffffff8020ea7c>] call_softirq+0x1c/0x3e
[<ffffffff8021047a>] do_softirq+0x94/0x1cd
[<ffffffff8026d5eb>] irq_exit+0x6b/0x10e
[<ffffffff8022e6ec>] smp_apic_timer_interrupt+0xd3/0xff
[<ffffffff8020e4b3>] apic_timer_interrupt+0x13/0x20
The code for cpu_avg_load_per_task has:
if (rq->nr_running)
rq->avg_load_per_task = rq->load.weight / rq->nr_running;
The runqueue lock is not held here, and there is nothing that prevents
the rq->nr_running from going to zero after it passes the if condition.
The branch profiler simply made the race window bigger.
This patch saves off the rq->nr_running to a local variable and uses that
for both the condition and the division.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: prevent unnecessary stack recursion
if the resched flag was set before we entered, then don't reschedule.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The user_ns is moved from nsproxy to user_struct, so that a struct
cred by itself is sufficient to determine access (which it otherwise
would not be). Corresponding ecryptfs fixes (by David Howells) are
here as well.
Fix refcounting. The following rules now apply:
1. The task pins the user struct.
2. The user struct pins its user namespace.
3. The user namespace pins the struct user which created it.
User namespaces are cloned during copy_creds(). Unsharing a new user_ns
is no longer possible. (We could re-add that, but it'll cause code
duplication and doesn't seem useful if PAM doesn't need to clone user
namespaces).
When a user namespace is created, its first user (uid 0) gets empty
keyrings and a clean group_info.
This incorporates a previous patch by David Howells. Here
is his original patch description:
>I suggest adding the attached incremental patch. It makes the following
>changes:
>
> (1) Provides a current_user_ns() macro to wrap accesses to current's user
> namespace.
>
> (2) Fixes eCryptFS.
>
> (3) Renames create_new_userns() to create_user_ns() to be more consistent
> with the other associated functions and because the 'new' in the name is
> superfluous.
>
> (4) Moves the argument and permission checks made for CLONE_NEWUSER to the
> beginning of do_fork() so that they're done prior to making any attempts
> at allocation.
>
> (5) Calls create_user_ns() after prepare_creds(), and gives it the new creds
> to fill in rather than have it return the new root user. I don't imagine
> the new root user being used for anything other than filling in a cred
> struct.
>
> This also permits me to get rid of a get_uid() and a free_uid(), as the
> reference the creds were holding on the old user_struct can just be
> transferred to the new namespace's creator pointer.
>
> (6) Makes create_user_ns() reset the UIDs and GIDs of the creds under
> preparation rather than doing it in copy_creds().
>
>David
>Signed-off-by: David Howells <dhowells@redhat.com>
Changelog:
Oct 20: integrate dhowells comments
1. leave thread_keyring alone
2. use current_user_ns() in set_user()
Signed-off-by: Serge Hallyn <serue@us.ibm.com>
Impact: fix mmiotrace overrun tracing
When ftrace framework moved to use the ring buffer facility, the buffer
overrun detection was broken after 2.6.27 by commit
| commit 3928a8a2d9
| Author: Steven Rostedt <rostedt@goodmis.org>
| Date: Mon Sep 29 23:02:41 2008 -0400
|
| ftrace: make work with new ring buffer
|
| This patch ports ftrace over to the new ring buffer.
The detection is now fixed by using the ring buffer API.
When mmiotrace detects a buffer overrun, it will report the number of
lost events. People reading an mmiotrace log must know if something was
missed, otherwise the data may not make sense.
Signed-off-by: Pekka Paalanen <pq@iki.fi>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: prettify /proc/lockdep_info
Just feel odd that not all lines of lockdep info are aligned.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: make output of stack_trace complete if buffer overruns
When read buffer overruns, the output of stack_trace isn't complete.
When printing records with seq_printf in t_show, if the read buffer
has overruned by the current record, then this record won't be
printed to user space through read buffer, it will just be dropped in
this printing.
When next printing, t_start should return the "*pos"th record, which
is the one dropped by previous printing, but it just returns
(m->private + *pos)th record.
Here we use a more sane method to implement seq_operations which can
be found in kernel code. Thus we needn't initialize m->private.
About testing, it's not easy to overrun read buffer, but we can use
seq_printf to print more padding bytes in t_show, then it's easy to
check whether or not records are lost.
This commit has been tested on both condition of overrun and non
overrun.
Signed-off-by: Liming Wang <liming.wang@windriver.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Try this, and you'll get oops immediately:
# cd Documentation/accounting/
# gcc -o getdelays getdelays.c
# mount -t cgroup -o debug xxx /mnt
# ./getdelays -C /mnt/tasks
Because a normal file's dentry->d_fsdata is a pointer to struct cftype,
not struct cgroup.
After the patch, it returns EINVAL if we try to get cgroupstats
from a normal file.
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Paul Menage <menage@google.com>
Cc: <stable@kernel.org> [2.6.25.x, 2.6.26.x, 2.6.27.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
sprint_symbol(), itself used when dumping stacks, has been wasting 128
bytes of stack: lookup the symbol directly into the buffer supplied by the
caller, instead of using a locally declared namebuf.
I believe the name != buffer strcpy() is obsolete: the design here dates
from when module symbol lookup pointed into a supposedly const but sadly
volatile table; nowadays it copies, but an uncalled strcpy() looks better
here than the risk of a recursive BUG_ON().
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
