linux-toradex.git/kernel/sys.c, branch v2.6.17.12

fix prctl privilege escalation and suid_dumpable (CVE-2006-2451)

2006-07-06T20:02:05+00:00

Based on a patch from Ernie Petrides

During security research, Red Hat discovered a behavioral flaw in core
dump handling. A local user could create a program that would cause a
core file to be dumped into a directory they would not normally have
permissions to write to. This could lead to a denial of service (disk
consumption), or allow the local user to gain root privileges.

Signed-off-by: Greg Kroah-Hartman

[PATCH] Make setsid() more robust

2006-03-31T20:18:59+00:00

The core problem: setsid fails if it is called by init.  The effect in 2.6.16
and the earlier kernels that have this problem is that if you do a "ps -j 1 or
ps -ej 1" you will see that init and several of it's children have process
group and session == 0.  Instead of process group == session == 1.  Despite
init calling setsid.

The reason it fails is that daemonize calls set_special_pids(1,1) on kernel
threads that are launched before /sbin/init is called.

The only remaining effect in that current->signal->leader == 0 for init
instead of 1.  And the setsid call fails.  No one has noticed because
/sbin/init does not check the return value of setsid.

In 2.4 where we don't have the pidhash table, and daemonize doesn't exist
setsid actually works for init.

I care a lot about pid == 1 not being a special case that we leave broken,
because of the container/jail work that I am doing.

- Carefully allow init (pid == 1) to call setsid despite the kernel using
  its session.

- Use find_task_by_pid instead of find_pid because find_pid taking a
  pidtype is going away.

Signed-off-by: Eric W. Biederman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] sys_times: don't take tasklist_lock

2006-03-29T02:36:43+00:00

sys_times: don't take tasklist_lock

Signed-off-by: Oleg Nesterov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] revert "Optimize sys_times for a single thread process"

2006-03-29T02:36:43+00:00

This patch reverts 'CONFIG_SMP && thread_group_empty()' optimization in
sys_times().  The reason is that the next patch breaks memory ordering which
is needed for that optimization.

tasklist_lock in sys_times() will be eliminated completely by further patch.

Signed-off-by: Oleg Nesterov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] Notifier chain update: API changes

2006-03-27T16:44:50+00:00

The kernel's implementation of notifier chains is unsafe.  There is no
protection against entries being added to or removed from a chain while the
chain is in use.  The issues were discussed in this thread:

    http://marc.theaimsgroup.com/?l=linux-kernel&m=113018709002036&w=2

We noticed that notifier chains in the kernel fall into two basic usage
classes:

	"Blocking" chains are always called from a process context
	and the callout routines are allowed to sleep;

	"Atomic" chains can be called from an atomic context and
	the callout routines are not allowed to sleep.

We decided to codify this distinction and make it part of the API.  Therefore
this set of patches introduces three new, parallel APIs: one for blocking
notifiers, one for atomic notifiers, and one for "raw" notifiers (which is
really just the old API under a new name).  New kinds of data structures are
used for the heads of the chains, and new routines are defined for
registration, unregistration, and calling a chain.  The three APIs are
explained in include/linux/notifier.h and their implementation is in
kernel/sys.c.

With atomic and blocking chains, the implementation guarantees that the chain
links will not be corrupted and that chain callers will not get messed up by
entries being added or removed.  For raw chains the implementation provides no
guarantees at all; users of this API must provide their own protections.  (The
idea was that situations may come up where the assumptions of the atomic and
blocking APIs are not appropriate, so it should be possible for users to
handle these things in their own way.)

There are some limitations, which should not be too hard to live with.  For
atomic/blocking chains, registration and unregistration must always be done in
a process context since the chain is protected by a mutex/rwsem.  Also, a
callout routine for a non-raw chain must not try to register or unregister
entries on its own chain.  (This did happen in a couple of places and the code
had to be changed to avoid it.)

Since atomic chains may be called from within an NMI handler, they cannot use
spinlocks for synchronization.  Instead we use RCU.  The overhead falls almost
entirely in the unregister routine, which is okay since unregistration is much
less frequent that calling a chain.

Here is the list of chains that we adjusted and their classifications.  None
of them use the raw API, so for the moment it is only a placeholder.

  ATOMIC CHAINS
  -------------
arch/i386/kernel/traps.c:		i386die_chain
arch/ia64/kernel/traps.c:		ia64die_chain
arch/powerpc/kernel/traps.c:		powerpc_die_chain
arch/sparc64/kernel/traps.c:		sparc64die_chain
arch/x86_64/kernel/traps.c:		die_chain
drivers/char/ipmi/ipmi_si_intf.c:	xaction_notifier_list
kernel/panic.c:				panic_notifier_list
kernel/profile.c:			task_free_notifier
net/bluetooth/hci_core.c:		hci_notifier
net/ipv4/netfilter/ip_conntrack_core.c:	ip_conntrack_chain
net/ipv4/netfilter/ip_conntrack_core.c:	ip_conntrack_expect_chain
net/ipv6/addrconf.c:			inet6addr_chain
net/netfilter/nf_conntrack_core.c:	nf_conntrack_chain
net/netfilter/nf_conntrack_core.c:	nf_conntrack_expect_chain
net/netlink/af_netlink.c:		netlink_chain

  BLOCKING CHAINS
  ---------------
arch/powerpc/platforms/pseries/reconfig.c:	pSeries_reconfig_chain
arch/s390/kernel/process.c:		idle_chain
arch/x86_64/kernel/process.c		idle_notifier
drivers/base/memory.c:			memory_chain
drivers/cpufreq/cpufreq.c		cpufreq_policy_notifier_list
drivers/cpufreq/cpufreq.c		cpufreq_transition_notifier_list
drivers/macintosh/adb.c:		adb_client_list
drivers/macintosh/via-pmu.c		sleep_notifier_list
drivers/macintosh/via-pmu68k.c		sleep_notifier_list
drivers/macintosh/windfarm_core.c	wf_client_list
drivers/usb/core/notify.c		usb_notifier_list
drivers/video/fbmem.c			fb_notifier_list
kernel/cpu.c				cpu_chain
kernel/module.c				module_notify_list
kernel/profile.c			munmap_notifier
kernel/profile.c			task_exit_notifier
kernel/sys.c				reboot_notifier_list
net/core/dev.c				netdev_chain
net/decnet/dn_dev.c:			dnaddr_chain
net/ipv4/devinet.c:			inetaddr_chain

It's possible that some of these classifications are wrong.  If they are,
please let us know or submit a patch to fix them.  Note that any chain that
gets called very frequently should be atomic, because the rwsem read-locking
used for blocking chains is very likely to incur cache misses on SMP systems.
(However, if the chain's callout routines may sleep then the chain cannot be
atomic.)

The patch set was written by Alan Stern and Chandra Seetharaman, incorporating
material written by Keith Owens and suggestions from Paul McKenney and Andrew
Morton.

[jes@sgi.com: restructure the notifier chain initialization macros]
Signed-off-by: Alan Stern 
Signed-off-by: Chandra Seetharaman 
Signed-off-by: Jes Sorensen 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] Use unsigned int types for a faster bsearch

2006-03-25T16:23:01+00:00

This patch avoids arithmetic on 'signed' types that are slower than
'unsigned'.  This saves space and cpu cycles.

size of kernel/sys.o before the patch (gcc-3.4.5)

    text    data     bss     dec     hex filename
   10924     252       4   11180    2bac kernel/sys.o

size of kernel/sys.o after the patch
    text    data     bss     dec     hex filename
   10903     252       4   11159    2b97 kernel/sys.o

I noticed that gcc-4.1.0 (from Fedora Core 5) even uses idiv instruction for
(a+b)/2 if a and b are signed.

Signed-off-by: Eric Dumazet 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] No need to protect current->group_info in sys_getgroups(), in_group_p() and in_egroup_p()

2006-03-25T16:22:58+00:00

While doing some benchmarks of an Apache/PHP SMP server, I noticed high
oprofile numbers in in_group_p() and _atomic_dec_and_lock().

rank  percent
  1     4.8911 % __link_path_walk
  2     4.8503 % __d_lookup
*3     4.2911 % _atomic_dec_and_lock
  4     3.9307 % __copy_to_user_ll
  5     4.9004 % sysenter_past_esp
*6     3.3248 % in_group_p

It appears that in_group_p() does an uncessary

get_group_info(current->group_info); /* atomic_inc() */
  ... /* access current->group_info */
put_group_info(current->group_info); /* _atomic_dec_and_lock */

It is not necessary to do this, because the current task holds a reference
on its own group_info, and this reference cannot change during the lookup.

This patch deletes the get_group_info()/put_group_info() pair from
sys_getgroups(), in_group_p() and in_egroup_p() functions.

Signed-off-by: Eric Dumazet 
Cc: Tim Hockin 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] refactor capable() to one implementation, add __capable() helper

2006-03-25T16:22:56+00:00

Move capable() to kernel/capability.c and eliminate duplicate
implementations.  Add __capable() function which can be used to check for
capabiilty of any process.

Signed-off-by: Chris Wright 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] RLIMIT_CPU: document wrong return value

2006-03-24T15:33:30+00:00

Document the fact that setrlimit(RLIMIT_CPU) doesn't return error codes when
it should.  I don't think we can fix this without a 2.7.x..

Cc: Martin Schwidefsky 
Cc: Ulrich Weigand 
Cc: Cliff Wickman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] RLIMIT_CPU: fix handling of a zero limit

2006-03-24T15:33:30+00:00

At present the kernel doesn't honour an attempt to set RLIMIT_CPU to zero
seconds.  But the spec says it should, and that's what 2.4.x does.

Fixing this for real would involve some complexity (such as adding a new
it-has-been-set flag to the task_struct, and testing that everwhere, instead
of overloading the value of it_prof_expires).

Given that a 2.4 kernel won't actually send the signal until one second has
expired anyway, let's just handle this case by treating the caller's
zero-seconds as one second.

Cc: Martin Schwidefsky 
Cc: Ulrich Weigand 
Cc: Cliff Wickman 
Acked-by: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds