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ARM: 7912/1: check stack pointer in get_wchan

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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

Cc: <stable@vger.kernel.org>
Signed-off-by: Konstantin Khlebnikov <k.khlebnikov@samsung.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Konstantin Khlebnikov 2013-12-05 14:21:36 +01:00 committed by Russell King
parent 7c927322d3
commit 1b15ec7a74
1 changed files with 5 additions and 2 deletions
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7
arch/arm/kernel/process.c
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@ -404,6 +404,7 @@ EXPORT_SYMBOL(dump_fpu);
unsigned long get_wchan(struct task_struct *p) unsigned long get_wchan(struct task_struct *p)
{ {
struct stackframe frame; struct stackframe frame;
unsigned long stack_page;
int count = 0; int count = 0;
if (!p || p == current || p->state == TASK_RUNNING) if (!p || p == current || p->state == TASK_RUNNING)
return 0; return 0;
@ -412,9 +413,11 @@ unsigned long get_wchan(struct task_struct *p)
frame.sp = thread_saved_sp(p); frame.sp = thread_saved_sp(p);
frame.lr = 0; /* recovered from the stack */ frame.lr = 0; /* recovered from the stack */
frame.pc = thread_saved_pc(p); frame.pc = thread_saved_pc(p);
stack_page = (unsigned long)task_stack_page(p);
do { do {
int ret = unwind_frame(&frame); if (frame.sp < stack_page ||
if (ret < 0) frame.sp >= stack_page + THREAD_SIZE ||
unwind_frame(&frame) < 0)
return 0; return 0;
if (!in_sched_functions(frame.pc)) if (!in_sched_functions(frame.pc))
return frame.pc; return frame.pc;