It's possible for get_task_cred() as it currently stands to 'corrupt' a set of
credentials by incrementing their usage count after their replacement by the
task being accessed.
What happens is that get_task_cred() can race with commit_creds():
TASK_1 TASK_2 RCU_CLEANER
-->get_task_cred(TASK_2)
rcu_read_lock()
__cred = __task_cred(TASK_2)
-->commit_creds()
old_cred = TASK_2->real_cred
TASK_2->real_cred = ...
put_cred(old_cred)
call_rcu(old_cred)
[__cred->usage == 0]
get_cred(__cred)
[__cred->usage == 1]
rcu_read_unlock()
-->put_cred_rcu()
[__cred->usage == 1]
panic()
However, since a tasks credentials are generally not changed very often, we can
reasonably make use of a loop involving reading the creds pointer and using
atomic_inc_not_zero() to attempt to increment it if it hasn't already hit zero.
If successful, we can safely return the credentials in the knowledge that, even
if the task we're accessing has released them, they haven't gone to the RCU
cleanup code.
We then change task_state() in procfs to use get_task_cred() rather than
calling get_cred() on the result of __task_cred(), as that suffers from the
same problem.
Without this change, a BUG_ON in __put_cred() or in put_cred_rcu() can be
tripped when it is noticed that the usage count is not zero as it ought to be,
for example:
kernel BUG at kernel/cred.c:168!
invalid opcode: 0000 [#1] SMP
last sysfs file: /sys/kernel/mm/ksm/run
CPU 0
Pid: 2436, comm: master Not tainted 2.6.33.3-85.fc13.x86_64 #1 0HR330/OptiPlex
745
RIP: 0010:[<ffffffff81069881>] [<ffffffff81069881>] __put_cred+0xc/0x45
RSP: 0018:ffff88019e7e9eb8 EFLAGS: 00010202
RAX: 0000000000000001 RBX: ffff880161514480 RCX: 00000000ffffffff
RDX: 00000000ffffffff RSI: ffff880140c690c0 RDI: ffff880140c690c0
RBP: ffff88019e7e9eb8 R08: 00000000000000d0 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000040 R12: ffff880140c690c0
R13: ffff88019e77aea0 R14: 00007fff336b0a5c R15: 0000000000000001
FS: 00007f12f50d97c0(0000) GS:ffff880007400000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8f461bc000 CR3: 00000001b26ce000 CR4: 00000000000006f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process master (pid: 2436, threadinfo ffff88019e7e8000, task ffff88019e77aea0)
Stack:
ffff88019e7e9ec8 ffffffff810698cd ffff88019e7e9ef8 ffffffff81069b45
<0> ffff880161514180 ffff880161514480 ffff880161514180 0000000000000000
<0> ffff88019e7e9f28 ffffffff8106aace 0000000000000001 0000000000000246
Call Trace:
[<ffffffff810698cd>] put_cred+0x13/0x15
[<ffffffff81069b45>] commit_creds+0x16b/0x175
[<ffffffff8106aace>] set_current_groups+0x47/0x4e
[<ffffffff8106ac89>] sys_setgroups+0xf6/0x105
[<ffffffff81009b02>] system_call_fastpath+0x16/0x1b
Code: 48 8d 71 ff e8 7e 4e 15 00 85 c0 78 0b 8b 75 ec 48 89 df e8 ef 4a 15 00
48 83 c4 18 5b c9 c3 55 8b 07 8b 07 48 89 e5 85 c0 74 04 <0f> 0b eb fe 65 48 8b
04 25 00 cc 00 00 48 3b b8 58 04 00 00 75
RIP [<ffffffff81069881>] __put_cred+0xc/0x45
RSP <ffff88019e7e9eb8>
---[ end trace df391256a100ebdd ]---
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The command
echo "file ec.c +p" >/sys/kernel/debug/dynamic_debug/control
causes an oops.
Move the call to ddebug_remove_module() down into free_module(). In this
way it should be called from all error paths. Currently, we are missing
the remove if the module init routine fails.
Signed-off-by: Jason Baron <jbaron@redhat.com>
Reported-by: Thomas Renninger <trenn@suse.de>
Tested-by: Thomas Renninger <trenn@suse.de>
Cc: <stable@kernel.org> [2.6.32+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The kdb code should not toggle the sysrq state in case an end user
wants to try and resume the normal kernel execution.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Immediately following an exit from the kdb shell the kgdb_connected
variable should be set to zero, unless there are breakpoints planted.
If the kgdb_connected variable is not zeroed out with kdb, it is
impossible to turn off kdb.
This patch is merely a work around for now, the real fix will check
for the breakpoints.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
In the process of merging kdb to the mainline, the kdb lsmod command
stopped printing the base load address of kernel modules. This is
needed for using kdb in conjunction with external tools such as gdb.
Simply restore the functionality by adding a kdb_printf for the base
load address of the kernel modules.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
The gdbserial protocol handler should return an empty packet instead
of an error string when ever it responds to a command it does not
implement.
The problem cases come from a debugger client sending
qTBuffer, qTStatus, qSearch, qSupported.
The incorrect response from the gdbstub leads the debugger clients to
not function correctly. Recent versions of gdb will not detach correctly as a result of this behavior.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Dongdong Deng <dongdong.deng@windriver.com>
Without this patch the "ll" linked-list traversal command won't
terminate when you hit q/Q.
Signed-off-by: Martin Hicks <mort@sgi.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
With commits 08677214 and 59be5a8e, alloc_bootmem()/free_bootmem() and
friends use the early_res functions for memory management when
NO_BOOTMEM is enabled. This patch adds the kmemleak calls in the
corresponding code paths for bootmem allocations.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Acked-by: Yinghai Lu <yinghai@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: stable@kernel.org
We should initialize the module dynamic debug datastructures
only after determining that the module is not loaded yet. This
fixes a bug that introduced in 2.6.35-rc2, where when a trying
to load a module twice, we also load it's dynamic printing data
twice which causes all sorts of nasty issues. Also handle
the dynamic debug cleanup later on failure.
Signed-off-by: Yehuda Sadeh <yehuda@hq.newdream.net>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (removed a #ifdef)
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
futex_find_get_task is currently used (through lookup_pi_state) from two
contexts, futex_requeue and futex_lock_pi_atomic. None of the paths
looks it needs the credentials check, though. Different (e)uids
shouldn't matter at all because the only thing that is important for
shared futex is the accessibility of the shared memory.
The credentail check results in glibc assert failure or process hang (if
glibc is compiled without assert support) for shared robust pthread
mutex with priority inheritance if a process tries to lock already held
lock owned by a process with a different euid:
pthread_mutex_lock.c:312: __pthread_mutex_lock_full: Assertion `(-(e)) != 3 || !robust' failed.
The problem is that futex_lock_pi_atomic which is called when we try to
lock already held lock checks the current holder (tid is stored in the
futex value) to get the PI state. It uses lookup_pi_state which in turn
gets task struct from futex_find_get_task. ESRCH is returned either
when the task is not found or if credentials check fails.
futex_lock_pi_atomic simply returns if it gets ESRCH. glibc code,
however, doesn't expect that robust lock returns with ESRCH because it
should get either success or owner died.
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Darren Hart <dvhltc@us.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When crashkernel is not enabled, "echo 0 > /sys/kernel/kexec_crash_size"
OOPSes the kernel in crash_shrink_memory. This happens when
crash_shrink_memory tries to release the 'crashk_res' resource which are
not reserved. Also value of "/sys/kernel/kexec_crash_size" shows as 1,
which should be 0.
This patch fixes the OOPS in crash_shrink_memory and shows
"/sys/kernel/kexec_crash_size" as 0 when crash kernel memory is not
reserved.
Signed-off-by: Pavan Naregundi <pavan@linux.vnet.ibm.com>
Reviewed-by: WANG Cong <xiyou.wangcong@gmail.com>
Cc: Simon Horman <horms@verge.net.au>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
GCC 4.4.1 on ARM has been observed to replace the while loop in
sched_avg_update with a call to uldivmod, resulting in the
following build failure at link-time:
kernel/built-in.o: In function `sched_avg_update':
kernel/sched.c:1261: undefined reference to `__aeabi_uldivmod'
kernel/sched.c:1261: undefined reference to `__aeabi_uldivmod'
make: *** [.tmp_vmlinux1] Error 1
This patch introduces a fake data hazard to the loop body to
prevent the compiler optimising the loop away.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: <stable@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Because cgroup_fork() is ran before sched_fork() [ from copy_process() ]
and the child's pid is not yet visible the child is pinned to its
cgroup. Therefore we can silence this warning.
A nicer solution would be moving cgroup_fork() to right after
dup_task_struct() and exclude PF_STARTING from task_subsys_state().
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The task_group() function returns a pointer that must be protected
by either RCU, the ->alloc_lock, or the cgroup lock (see the
rcu_dereference_check() in task_subsys_state(), which is invoked by
task_group()). The wake_affine() function currently does none of these,
which means that a concurrent update would be within its rights to free
the structure returned by task_group(). Because wake_affine() uses this
structure only to compute load-balancing heuristics, there is no reason
to acquire either of the two locks.
Therefore, this commit introduces an RCU read-side critical section that
starts before the first call to task_group() and ends after the last use
of the "tg" pointer returned from task_group(). Thanks to Li Zefan for
pointing out the need to extend the RCU read-side critical section from
that proposed by the original patch.
Signed-off-by: Daniel J Blueman <daniel.blueman@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Commit e70971591 ("sched: Optimize unused cgroup configuration") introduced
an imbalanced scheduling bug.
If we do not use CGROUP, function update_h_load won't update h_load. When the
system has a large number of tasks far more than logical CPU number, the
incorrect cfs_rq[cpu]->h_load value will cause load_balance() to pull too
many tasks to the local CPU from the busiest CPU. So the busiest CPU keeps
going in a round robin. That will hurt performance.
The issue was found originally by a scientific calculation workload that
developed by Yanmin. With that commit, the workload performance drops
about 40%.
CPU before after
00 : 2 : 7
01 : 1 : 7
02 : 11 : 6
03 : 12 : 7
04 : 6 : 6
05 : 11 : 7
06 : 10 : 6
07 : 12 : 7
08 : 11 : 6
09 : 12 : 6
10 : 1 : 6
11 : 1 : 6
12 : 6 : 6
13 : 2 : 6
14 : 2 : 6
15 : 1 : 6
Reviewed-by: Yanmin zhang <yanmin.zhang@intel.com>
Signed-off-by: Alex Shi <alex.shi@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1276754893.9452.5442.camel@debian>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Chris Wedgwood reports that 39c0cbe (sched: Rate-limit nohz) causes a
serial console regression, unresponsiveness, and indeed it does. The
reason is that the nohz code is skipped even when the tick was already
stopped before the nohz_ratelimit(cpu) condition changed.
Move the nohz_ratelimit() check to the other conditions which prevent
long idle sleeps.
Reported-by: Chris Wedgwood <cw@f00f.org>
Tested-by: Brian Bloniarz <bmb@athenacr.com>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Greg KH <gregkh@suse.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Jef Driesen <jefdriesen@telenet.be>
LKML-Reference: <1276790557.27822.516.camel@twins>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
With the addition of the code to shrink the kernel tracepoint
infrastructure, we lost kprobes being traced by perf. The reason
is that I tested if the "tp_event->class->perf_probe" existed before
enabling it. This prevents "ftrace only" events (like the function
trace events) from being enabled by perf.
Unfortunately, kprobe events do not use perf_probe. This causes
kprobes to be missed by perf. To fix this, we add the test to
see if "tp_event->class->reg" exists as well as perf_probe.
Normal trace events have only "perf_probe" but no "reg" function,
and kprobes and syscalls have the "reg" but no "perf_probe".
The ftrace unique events do not have either, so this is a valid
test. If a kprobe or syscall is not to be probed by perf, the
"reg" function is called anyway, and will return a failure and
prevent perf from probing it.
Reported-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Tested-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
