From: Russell King <rmk+kernel@arm.linux.org.uk>
Date: Sat, 15 Jan 2011 09:27:04 +0000 (+0000)
Subject: ARM: fix /proc/$PID/stack on SMP
X-Git-Tag: v2.6.38-rc1~39^2~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d5996b2ff0e26cf7ed4c103084a2d6fc569e7216;p=pandora-kernel.git

ARM: fix /proc/$PID/stack on SMP

Rabin Vincent reports:
| On SMP, this BUG() in save_stack_trace_tsk() can be easily triggered
| from user space by reading /proc/$PID/stack, where $PID is any pid but
| the current process:
|
|	if (tsk != current) {
| #ifdef CONFIG_SMP
|		/*
|		 * What guarantees do we have here that 'tsk'
|		 * is not running on another CPU?
|		 */
|		BUG();
| #else

Fix this by replacing the BUG() with an entry to terminate the stack
trace, returning an empty trace - I'd rather not expose the dwarf
unwinder to a volatile stack of a running thread.

Reported-by: Rabin Vincent <rabin@rab.in>
Tested-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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