[tip:sched/core] signals, ptrace, sched: Fix a misaligned load inside ptrace_attach()

[tip-bot for Palmer Dabbelt]

Commit-ID:  e7cc4173115347bcdaa5de2824dd46ef2c58425f
Gitweb:     http://git.kernel.org/tip/e7cc4173115347bcdaa5de2824dd46ef2c58425f
Author:     Palmer Dabbelt <palmer@xxxxxxxxxxx>
AuthorDate: Thu, 30 Apr 2015 21:19:55 -0700
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 8 May 2015 12:06:57 +0200

signals, ptrace, sched: 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.

Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Chris Metcalf <cmetcalf@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: bobby.prani@xxxxxxxxx
Cc: oleg@xxxxxxxxxx
Cc: paulmck@xxxxxxxxxxxxxxxxxx
Cc: richard@xxxxxx
Cc: vdavydov@xxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1430453997-32459-2-git-send-email-palmer@xxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 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 4f066cb..fb650a2 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1374,7 +1374,7 @@ 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;
--
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