linux-kernel - [PATCH 1/3] Fix a misaligned load inside ptrace

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Message-Id: <1430453997-32459-2-git-send-email-palmer@dabbelt.com>
Date:	Thu, 30 Apr 2015 21:19:55 -0700
From:	Palmer Dabbelt <palmer@...belt.com>
To:	vdavydov@...allels.com
Cc:	Palmer Dabbelt <palmer@...belt.com>
Subject: [PATCH 1/3] Fix a misaligned load inside ptrace_attach()

The misaligned load exception arises when running ptrace_attach() on
the RISC-V (which hasn't been upstreamed yet).  The problem is that
wait_on_bit() takes a void* but then proceeds to call test_bit(),
which takes a long*.  This allows an int-aligned pointer to be passed
to test_bit(), which promptly fails.  This will manifest on any other
asm-generic port where unaligned loads trap, where sizeof(long) >
sizeof(int), and where task_struct.jobctl ends up not being
long-aligned.

This patch changes task_struct.jobctl to be a long, which ensures it
has the correct alignment.

Reviewed-by: Chris Metcalf <cmetcalf@...hip.com>
Signed-off-by: Palmer Dabbelt <palmer@...belt.com>
---
 include/linux/sched.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 26a2e6122734..391827db0a2d 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1369,7 +1369,7 @@ struct task_struct {
 	int exit_state;
 	int exit_code, exit_signal;
 	int pdeath_signal;  /*  The signal sent when the parent dies  */
-	unsigned int jobctl;	/* JOBCTL_*, siglock protected */
+	unsigned long jobctl;	/* JOBCTL_*, siglock protected */

 	/* Used for emulating ABI behavior of previous Linux versions */
 	unsigned int personality;
-- 
2.0.5

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