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cd0980fc8a
Most arch syscall_get_nr() implementations returns -1 if the syscall
number is not valid. Accessing the bit field without a check might
result in a kernel oops (at least I saw it on s390 for ftrace selftest).
Before this change, this problem did not occur, because the invalid
syscall number (-1) caused syscall_nr_to_meta() to return NULL.
There are at least two scenarios where syscall_get_nr() can return -1:
1. For example, ptrace stores an invalid syscall number, and thus,
tracing code resets it.
(see do_syscall_trace_enter in arch/s390/kernel/ptrace.c)
2. The syscall_regfunc() (kernel/tracepoint.c) sets the
TIF_SYSCALL_FTRACE (now: TIF_SYSCALL_TRACEPOINT) flag for all threads
which include kernel threads.
However, the ftrace selftest triggers a kernel oops when testing
syscall trace points:
- The kernel thread is started as ususal (do_fork()),
- tracing code sets TIF_SYSCALL_FTRACE,
- the ret_from_fork() function is triggered and starts
ftrace_syscall_exit() with an invalid syscall number.
To avoid these scenarios, I suggest to check the syscall_nr.
For instance, the ftrace selftest fails for s390 (with config option
CONFIG_FTRACE_SYSCALLS set) and produces the following kernel oops.
Unable to handle kernel pointer dereference at virtual kernel address 2000000000
Oops: 0038 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 Not tainted 2.6.31-rc6-next-20090819-dirty #18
Process kthreadd (pid: 818, task: 000000003ea207e8, ksp: 000000003e813eb8)
Krnl PSW : 0704100180000000 00000000000ea54c (ftrace_syscall_exit+0x58/0xdc)
R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:0 CC:1 PM:0 EA:3
Krnl GPRS: 0000000000000000 00000000000e0000 ffffffffffffffff 20000000008c2650
0000000000000007 0000000000000000 0000000000000000 0000000000000000
0000000000000000 0000000000000000 ffffffffffffffff 000000003e813d78
000000003e813f58 0000000000505ba8 000000003e813e18 000000003e813d78
Krnl Code: 00000000000ea540: e330d0000008 ag %r3,0(%r13)
00000000000ea546: a7480007 lhi %r4,7
00000000000ea54a: 1442 nr %r4,%r2
>00000000000ea54c: e31030000090 llgc %r1,0(%r3)
00000000000ea552: 5410d008 n %r1,8(%r13)
00000000000ea556: 8a104000 sra %r1,0(%r4)
00000000000ea55a: 5410d00c n %r1,12(%r13)
00000000000ea55e: 1211 ltr %r1,%r1
Call Trace:
([<0000000000000000>] 0x0)
[<000000000001fa22>] do_syscall_trace_exit+0x132/0x18c
[<000000000002d0c4>] sysc_return+0x0/0x8
[<000000000001c738>] kernel_thread_starter+0x0/0xc
Last Breaking-Event-Address:
[<00000000000ea51e>] ftrace_syscall_exit+0x2a/0xdc
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Jiaying Zhang <jiayingz@google.com>
Cc: Martin Bligh <mbligh@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
LKML-Reference: <20090825125027.GE4639@cetus.boeblingen.de.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
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| .. | ||
| gcov | ||
| irq | ||
| power | ||
| time | ||
| trace | ||
| .gitignore | ||
| acct.c | ||
| async.c | ||
| audit.c | ||
| audit.h | ||
| audit_tree.c | ||
| audit_watch.c | ||
| auditfilter.c | ||
| auditsc.c | ||
| backtracetest.c | ||
| bounds.c | ||
| capability.c | ||
| cgroup.c | ||
| cgroup_debug.c | ||
| cgroup_freezer.c | ||
| compat.c | ||
| configs.c | ||
| cpu.c | ||
| cpuset.c | ||
| cred-internals.h | ||
| cred.c | ||
| delayacct.c | ||
| dma-coherent.c | ||
| dma.c | ||
| exec_domain.c | ||
| exit.c | ||
| extable.c | ||
| fork.c | ||
| freezer.c | ||
| futex.c | ||
| futex_compat.c | ||
| groups.c | ||
| hrtimer.c | ||
| hung_task.c | ||
| itimer.c | ||
| kallsyms.c | ||
| Kconfig.freezer | ||
| Kconfig.hz | ||
| Kconfig.preempt | ||
| kexec.c | ||
| kfifo.c | ||
| kgdb.c | ||
| kmod.c | ||
| kprobes.c | ||
| ksysfs.c | ||
| kthread.c | ||
| latencytop.c | ||
| lockdep.c | ||
| lockdep_internals.h | ||
| lockdep_proc.c | ||
| lockdep_states.h | ||
| Makefile | ||
| marker.c | ||
| module.c | ||
| mutex-debug.c | ||
| mutex-debug.h | ||
| mutex.c | ||
| mutex.h | ||
| notifier.c | ||
| ns_cgroup.c | ||
| nsproxy.c | ||
| panic.c | ||
| params.c | ||
| perf_counter.c | ||
| pid.c | ||
| pid_namespace.c | ||
| pm_qos_params.c | ||
| posix-cpu-timers.c | ||
| posix-timers.c | ||
| printk.c | ||
| profile.c | ||
| ptrace.c | ||
| rcuclassic.c | ||
| rcupdate.c | ||
| rcupreempt.c | ||
| rcupreempt_trace.c | ||
| rcutorture.c | ||
| rcutree.c | ||
| rcutree.h | ||
| rcutree_trace.c | ||
| relay.c | ||
| res_counter.c | ||
| resource.c | ||
| rtmutex-debug.c | ||
| rtmutex-debug.h | ||
| rtmutex-tester.c | ||
| rtmutex.c | ||
| rtmutex.h | ||
| rtmutex_common.h | ||
| rwsem.c | ||
| sched.c | ||
| sched_clock.c | ||
| sched_cpupri.c | ||
| sched_cpupri.h | ||
| sched_debug.c | ||
| sched_fair.c | ||
| sched_features.h | ||
| sched_idletask.c | ||
| sched_rt.c | ||
| sched_stats.h | ||
| seccomp.c | ||
| semaphore.c | ||
| signal.c | ||
| slow-work.c | ||
| smp.c | ||
| softirq.c | ||
| softlockup.c | ||
| spinlock.c | ||
| srcu.c | ||
| stacktrace.c | ||
| stop_machine.c | ||
| sys.c | ||
| sys_ni.c | ||
| sysctl.c | ||
| sysctl_check.c | ||
| taskstats.c | ||
| test_kprobes.c | ||
| time.c | ||
| timeconst.pl | ||
| timer.c | ||
| tracepoint.c | ||
| tsacct.c | ||
| uid16.c | ||
| up.c | ||
| user.c | ||
| user_namespace.c | ||
| utsname.c | ||
| utsname_sysctl.c | ||
| wait.c | ||
| workqueue.c | ||