linux/kernel, branch v2.6.35.8

hrtimer: Preserve timer state in remove_hrtimer()

2010-10-29T04:51:24Z

commit f13d4f979c518119bba5439dd2364d76d31dcd3f upstream. The race is described as follows: CPU X CPU Y remove_hrtimer // state & QUEUED == 0 timer->state = CALLBACK unlock timer base timer->f(n) //very long hrtimer_start lock timer base remove_hrtimer // no effect hrtimer_enqueue timer->state = CALLBACK | QUEUED unlock timer base hrtimer_start lock timer base remove_hrtimer mode = INACTIVE // CALLBACK bit lost! switch_hrtimer_base CALLBACK bit not set: timer->base changes to a different CPU. lock this CPU's timer base The bug was introduced with commit ca109491f (hrtimer: removing all ur callback modes) in 2.6.29 [ tglx: Feed new state via local variable and add a comment. ] Signed-off-by: Salman Qazi Cc: akpm@linux-foundation.org Cc: Peter Zijlstra LKML-Reference: <20101012142351.8485.21823.stgit@dungbeetle.mtv.corp.google.com> Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman

ring-buffer: Fix typo of time extends per page

2010-10-29T04:51:23Z

commit d01343244abdedd18303d0323b518ed9cdcb1988 upstream. Time stamps for the ring buffer are created by the difference between two events. Each page of the ring buffer holds a full 64 bit timestamp. Each event has a 27 bit delta stamp from the last event. The unit of time is nanoseconds, so 27 bits can hold ~134 milliseconds. If two events happen more than 134 milliseconds apart, a time extend is inserted to add more bits for the delta. The time extend has 59 bits, which is good for ~18 years. Currently the time extend is committed separately from the event. If an event is discarded before it is committed, due to filtering, the time extend still exists. If all events are being filtered, then after ~134 milliseconds a new time extend will be added to the buffer. This can only happen till the end of the page. Since each page holds a full timestamp, there is no reason to add a time extend to the beginning of a page. Time extends can only fill a page that has actual data at the beginning, so there is no fear that time extends will fill more than a page without any data. When reading an event, a loop is made to skip over time extends since they are only used to maintain the time stamp and are never given to the caller. As a paranoid check to prevent the loop running forever, with the knowledge that time extends may only fill a page, a check is made that tests the iteration of the loop, and if the iteration is more than the number of time extends that can fit in a page a warning is printed and the ring buffer is disabled (all of ftrace is also disabled with it). There is another event type that is called a TIMESTAMP which can hold 64 bits of data in the theoretical case that two events happen 18 years apart. This code has not been implemented, but the name of this event exists, as well as the structure for it. The size of a TIMESTAMP is 16 bytes, where as a time extend is only 8 bytes. The macro used to calculate how many time extends can fit on a page used the TIMESTAMP size instead of the time extend size cutting the amount in half. The following test case can easily trigger the warning since we only need to have half the page filled with time extends to trigger the warning: # cd /sys/kernel/debug/tracing/ # echo function > current_tracer # echo 'common_pid < 0' > events/ftrace/function/filter # echo > trace # echo 1 > trace_marker # sleep 120 # cat trace Enabling the function tracer and then setting the filter to only trace functions where the process id is negative (no events), then clearing the trace buffer to ensure that we have nothing in the buffer, then write to trace_marker to add an event to the beginning of a page, sleep for 2 minutes (only 35 seconds is probably needed, but this guarantees the bug), and then finally reading the trace which will trigger the bug. This patch fixes the typo and prevents the false positive of that warning. Reported-by: Hans J. Koch Tested-by: Hans J. Koch Cc: Thomas Gleixner Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman

Fix unprotected access to task credentials in waitid()

2010-09-27T00:18:41Z

commit f362b73244fb16ea4ae127ced1467dd8adaa7733 upstream. Using a program like the following: #include #include #include #include int main() { id_t id; siginfo_t infop; pid_t res; id = fork(); if (id == 0) { sleep(1); exit(0); } kill(id, SIGSTOP); alarm(1); waitid(P_PID, id, &infop, WCONTINUED); return 0; } to call waitid() on a stopped process results in access to the child task's credentials without the RCU read lock being held - which may be replaced in the meantime - eliciting the following warning: =================================================== [ INFO: suspicious rcu_dereference_check() usage. ] --------------------------------------------------- kernel/exit.c:1460 invoked rcu_dereference_check() without protection! other info that might help us debug this: rcu_scheduler_active = 1, debug_locks = 1 2 locks held by waitid02/22252: #0: (tasklist_lock){.?.?..}, at: [] do_wait+0xc5/0x310 #1: (&(&sighand->siglock)->rlock){-.-...}, at: [] wait_consider_task+0x19a/0xbe0 stack backtrace: Pid: 22252, comm: waitid02 Not tainted 2.6.35-323cd+ #3 Call Trace: [] lockdep_rcu_dereference+0xa4/0xc0 [] wait_consider_task+0xaf1/0xbe0 [] do_wait+0xf5/0x310 [] sys_waitid+0x86/0x1f0 [] ? child_wait_callback+0x0/0x70 [] system_call_fastpath+0x16/0x1b This is fixed by holding the RCU read lock in wait_task_continued() to ensure that the task's current credentials aren't destroyed between us reading the cred pointer and us reading the UID from those credentials. Furthermore, protect wait_task_stopped() in the same way. We don't need to keep holding the RCU read lock once we've read the UID from the credentials as holding the RCU read lock doesn't stop the target task from changing its creds under us - so the credentials may be outdated immediately after we've read the pointer, lock or no lock. Signed-off-by: Daniel J Blueman Signed-off-by: David Howells Acked-by: Paul E. McKenney Acked-by: Oleg Nesterov Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

PM / Hibernate: Avoid hitting OOM during preallocation of memory

2010-09-27T00:18:38Z

commit 6715045ddc7472a22be5e49d4047d2d89b391f45 upstream. There is a problem in hibernate_preallocate_memory() that it calls preallocate_image_memory() with an argument that may be greater than the total number of available non-highmem memory pages. If that's the case, the OOM condition is guaranteed to trigger, which in turn can cause significant slowdown to occur during hibernation. To avoid that, make preallocate_image_memory() adjust its argument before calling preallocate_image_pages(), so that the total number of saveable non-highem pages left is not less than the minimum size of a hibernation image. Change hibernate_preallocate_memory() to try to allocate from highmem if the number of pages allocated by preallocate_image_memory() is too low. Modify free_unnecessary_pages() to take all possible memory allocation patterns into account. Reported-by: KOSAKI Motohiro Signed-off-by: Rafael J. Wysocki Tested-by: M. Vefa Bicakci Signed-off-by: Greg Kroah-Hartman

sched: Fix user time incorrectly accounted as system time on 32-bit

2010-09-27T00:18:23Z

commit e75e863dd5c7d96b91ebbd241da5328fc38a78cc upstream. We have 32-bit variable overflow possibility when multiply in task_times() and thread_group_times() functions. When the overflow happens then the scaled utime value becomes erroneously small and the scaled stime becomes i erroneously big. Reported here: https://bugzilla.redhat.com/show_bug.cgi?id=633037 https://bugzilla.kernel.org/show_bug.cgi?id=16559 Reported-by: Michael Chapman Reported-by: Ciriaco Garcia de Celis Signed-off-by: Stanislaw Gruszka Signed-off-by: Peter Zijlstra Cc: Hidetoshi Seto LKML-Reference: <20100914143513.GB8415@redhat.com> Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

pid: make setpgid() system call use RCU read-side critical section

2010-09-27T00:18:22Z

commit 950eaaca681c44aab87a46225c9e44f902c080aa upstream. [ 23.584719] [ 23.584720] =================================================== [ 23.585059] [ INFO: suspicious rcu_dereference_check() usage. ] [ 23.585176] --------------------------------------------------- [ 23.585176] kernel/pid.c:419 invoked rcu_dereference_check() without protection! [ 23.585176] [ 23.585176] other info that might help us debug this: [ 23.585176] [ 23.585176] [ 23.585176] rcu_scheduler_active = 1, debug_locks = 1 [ 23.585176] 1 lock held by rc.sysinit/728: [ 23.585176] #0: (tasklist_lock){.+.+..}, at: [] sys_setpgid+0x5f/0x193 [ 23.585176] [ 23.585176] stack backtrace: [ 23.585176] Pid: 728, comm: rc.sysinit Not tainted 2.6.36-rc2 #2 [ 23.585176] Call Trace: [ 23.585176] [] lockdep_rcu_dereference+0x99/0xa2 [ 23.585176] [] find_task_by_pid_ns+0x50/0x6a [ 23.585176] [] find_task_by_vpid+0x1d/0x1f [ 23.585176] [] sys_setpgid+0x67/0x193 [ 23.585176] [] system_call_fastpath+0x16/0x1b [ 24.959669] type=1400 audit(1282938522.956:4): avc: denied { module_request } for pid=766 comm="hwclock" kmod="char-major-10-135" scontext=system_u:system_r:hwclock_t:s0 tcontext=system_u:system_r:kernel_t:s0 tclas It turns out that the setpgid() system call fails to enter an RCU read-side critical section before doing a PID-to-task_struct translation. This commit therefore does rcu_read_lock() before the translation, and also does rcu_read_unlock() after the last use of the returned pointer. Reported-by: Andrew Morton Signed-off-by: Paul E. McKenney Acked-by: David Howells Cc: Jiri Slaby Cc: Oleg Nesterov Signed-off-by: Greg Kroah-Hartman

hw breakpoints: Fix pid namespace bug

2010-09-27T00:18:22Z

commit 068e35eee9ef98eb4cab55181977e24995d273be upstream. Hardware breakpoints can't be registered within pid namespaces because tsk->pid is passed rather than the pid in the current namespace. (See https://bugzilla.kernel.org/show_bug.cgi?id=17281 ) This is a quick fix demonstrating the problem but is not the best method of solving the problem since passing pids internally is not the best way to avoid pid namespace bugs. Subsequent patches will show a better solution. Much thanks to Frederic Weisbecker for doing the bulk of the work finding this bug. Reported-by: Robin Green Signed-off-by: Matt Helsley Signed-off-by: Peter Zijlstra Cc: Prasad Cc: Arnaldo Carvalho de Melo Cc: Steven Rostedt Cc: Will Deacon Cc: Mahesh Salgaonkar LKML-Reference: Signed-off-by: Ingo Molnar Signed-off-by: Frederic Weisbecker Signed-off-by: Greg Kroah-Hartman

compat: Make compat_alloc_user_space() incorporate the access_ok()

2010-09-20T20:36:44Z

commit c41d68a513c71e35a14f66d71782d27a79a81ea6 upstream. compat_alloc_user_space() expects the caller to independently call access_ok() to verify the returned area. A missing call could introduce problems on some architectures. This patch incorporates the access_ok() check into compat_alloc_user_space() and also adds a sanity check on the length. The existing compat_alloc_user_space() implementations are renamed arch_compat_alloc_user_space() and are used as part of the implementation of the new global function. This patch assumes NULL will cause __get_user()/__put_user() to either fail or access userspace on all architectures. This should be followed by checking the return value of compat_access_user_space() for NULL in the callers, at which time the access_ok() in the callers can also be removed. Reported-by: Ben Hawkes Signed-off-by: H. Peter Anvin Acked-by: Benjamin Herrenschmidt Acked-by: Chris Metcalf Acked-by: David S. Miller Acked-by: Ingo Molnar Acked-by: Thomas Gleixner Acked-by: Tony Luck Cc: Andrew Morton Cc: Arnd Bergmann Cc: Fenghua Yu Cc: H. Peter Anvin Cc: Heiko Carstens Cc: Helge Deller Cc: James Bottomley Cc: Kyle McMartin Cc: Martin Schwidefsky Cc: Paul Mackerras Cc: Ralf Baechle Signed-off-by: Greg Kroah-Hartman

kernel/groups.c: fix integer overflow in groups_search

2010-09-20T20:36:38Z

commit 1c24de60e50fb19b94d94225458da17c720f0729 upstream. gid_t is a unsigned int. If group_info contains a gid greater than MAX_INT, groups_search() function may look on the wrong side of the search tree. This solves some unfair "permission denied" problems. Signed-off-by: Jerome Marchand Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

gcov: fix null-pointer dereference for certain module types

2010-09-20T20:36:35Z

commit 85a0fdfd0f967507f3903e8419bc7e408f5a59de upstream. The gcov-kernel infrastructure expects that each object file is loaded only once. This may not be true, e.g. when loading multiple kernel modules which are linked to the same object file. As a result, loading such kernel modules will result in incorrect gcov results while unloading will cause a null-pointer dereference. This patch fixes these problems by changing the gcov-kernel infrastructure so that multiple profiling data sets can be associated with one debugfs entry. It applies to 2.6.36-rc1. Signed-off-by: Peter Oberparleiter Reported-by: Werner Spies Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman