3.2.54-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Konstantin Khlebnikov <k.khlebni...@samsung.com> commit 1b15ec7a7427d4188ba91b9bbac696250a059d22 upstream. get_wchan() is lockless. Task may wakeup at any time and change its own stack, thus each next stack frame may be overwritten and filled with random stuff. /proc/$pid/stack interface had been disabled for non-current tasks, see [1] But 'wchan' still allows to trigger stack frame unwinding on volatile stack. This patch fixes oops in unwind_frame() by adding stack pointer validation on each step (as x86 code do), unwind_frame() already checks frame pointer. Also I've found another report of this oops on stackoverflow (irony). Link: http://www.spinics.net/lists/arm-kernel/msg110589.html [1] Link: http://stackoverflow.com/questions/18479894/unwind-frame-cause-a-kernel-paging-error Signed-off-by: Konstantin Khlebnikov <k.khlebni...@samsung.com> Acked-by: Will Deacon <will.dea...@arm.com> Signed-off-by: Russell King <rmk+ker...@arm.linux.org.uk> Signed-off-by: Ben Hutchings <b...@decadent.org.uk> --- arch/arm/kernel/process.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -468,6 +468,7 @@ EXPORT_SYMBOL(kernel_thread); unsigned long get_wchan(struct task_struct *p) { struct stackframe frame; + unsigned long stack_page; int count = 0; if (!p || p == current || p->state == TASK_RUNNING) return 0; @@ -476,9 +477,11 @@ unsigned long get_wchan(struct task_stru frame.sp = thread_saved_sp(p); frame.lr = 0; /* recovered from the stack */ frame.pc = thread_saved_pc(p); + stack_page = (unsigned long)task_stack_page(p); do { - int ret = unwind_frame(&frame); - if (ret < 0) + if (frame.sp < stack_page || + frame.sp >= stack_page + THREAD_SIZE || + unwind_frame(&frame) < 0) return 0; if (!in_sched_functions(frame.pc)) return frame.pc; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
