From mboxrd@z Thu Jan 1 00:00:00 1970 From: k.khlebnikov@samsung.com (Konstantin Khlebnikov) Date: Fri, 15 Nov 2013 16:19:07 +0400 Subject: [PATCH] arm: check stack pointer in get_wchan Message-ID: <20131115121907.4707.82671.stgit@buzz> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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). Signed-off-by: Konstantin Khlebnikov Cc: Vyacheslav Tyrtov Link: http://www.spinics.net/lists/arm-kernel/msg110589.html [1] Link: http://stackoverflow.com/questions/18479894/unwind-frame-cause-a-kernel-paging-error --- arch/arm/kernel/process.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c index 94f6b05..92f7b15 100644 --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -404,6 +404,7 @@ EXPORT_SYMBOL(dump_fpu); 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; @@ -412,9 +413,11 @@ unsigned long get_wchan(struct task_struct *p) 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; From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752604Ab3KOMTT (ORCPT ); Fri, 15 Nov 2013 07:19:19 -0500 Received: from mailout1.w1.samsung.com ([210.118.77.11]:14704 "EHLO mailout1.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750861Ab3KOMTL (ORCPT ); Fri, 15 Nov 2013 07:19:11 -0500 X-AuditID: cbfec7f5-b7fe66d00000432e-ba-5286113c40dd Subject: [PATCH] arm: check stack pointer in get_wchan To: Russell King From: Konstantin Khlebnikov Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Vyacheslav Tyrtov Date: Fri, 15 Nov 2013 16:19:07 +0400 Message-id: <20131115121907.4707.82671.stgit@buzz> User-Agent: StGit/0.15 MIME-version: 1.0 Content-type: text/plain; charset=utf-8 Content-transfer-encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFupmluLIzCtJLcpLzFFi42I5/e/4FV0bwbYgg4vTDS02Pb7GanF51xw2 i9uXeS2mzvjB7sDi0dLcw+axeUm9R9+WVYwenzfJBbBEcdmkpOZklqUW6dslcGV8PXaFuWAq X8Wt51dYGxivcXcxcnBICJhINNzN7mLkBDLFJC7cW8/WxcjFISSwlFHiftNGJginkUni9+Hd LCANwgJmEheviII0iAhoSpxafJEZxGYDCm/bd5sRxGYWKJLoudHGBmKzCKhKPPhzlQmklVfA SGL1LjmQsCjQrjWXTjKB2LwCghI/Jt8Dm84soC4xZUouxBR5ic1r3jJPYOSbhaRqFkLVLCRV CxiZVzGKppYmFxQnpeca6RUn5haX5qXrJefnbmKEBODXHYxLj1kdYhTgYFTi4Y2Qbg0SYk0s K67MPcQowcGsJMJ79w1QiDclsbIqtSg/vqg0J7X4ECMTB6dUA2NcOqcHS6IKU/N/wWk/NWaf UEi3+d5aEuX/pGmqmqLDg2XHrp8IYO65detj4EP/o7nSGlfmWD9gXzaN4/01+77P1UzRk3Uv vPTiS15mLGqucZ1FtSl4aem1XVYWNc637Q79WXLJbprByfqqKZvZvkVYBXFPvyxfcEX13ucS x4UZ/mKrZJ+deKbEUpyRaKjFXFScCACmR8w3HgIAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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). Signed-off-by: Konstantin Khlebnikov Cc: Vyacheslav Tyrtov Link: http://www.spinics.net/lists/arm-kernel/msg110589.html [1] Link: http://stackoverflow.com/questions/18479894/unwind-frame-cause-a-kernel-paging-error --- arch/arm/kernel/process.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c index 94f6b05..92f7b15 100644 --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -404,6 +404,7 @@ EXPORT_SYMBOL(dump_fpu); 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; @@ -412,9 +413,11 @@ unsigned long get_wchan(struct task_struct *p) 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;