[PATCH 0/3] Fix a misaligned load inside ptrace_attach()

[PATCH 0/3] Fix a misaligned load inside ptrace_attach()

[Palmer Dabbelt]

I ran across what I believe is a bug in some asm-generic code while
working on the RISC-V Linux port.  Essentially the problem is that
wait_on_bit() takes a void *, but then perfroms long-aligned
operation.  As far as I can tell, this bug could manifest on any other
architecture that doesn't support misaligned operations and uses this
particular asm-generic implementation.

The patch set is split into three parts:

* #1 fixes the bug by making task_struct.jobctl an unsigned long,
   which ensures wait_on_bit() always ends up with a long-aligned
   argument.

* #2 changes the prototype of wait_on_bit() and friends to take a
   "unsigned long *" instead of a "void *", with the intent of
   ensuring these problems don't happen again.

* #3 is a bit more intrusive: it goes and changes all uses of
   task_struct.jobctl from int to long.

I'm not sure if #3 has gone too far, but I think #1 and #2 are sane.
The cost is making task_struct larger on machines where
sizeof(long)>sizeof(int), but since it's so big already this isn't too
much cost.  I thought about making test_bit() perform byte-aligned
accesses to avoid this cost, but since there are very similar looking
atomic functions I thought that would be too odd.

[PATCH 1/3] Fix a misaligned load inside ptrace_attach()

[Palmer Dabbelt]

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@ezchip.com>
Signed-off-by: Palmer Dabbelt <palmer@dabbelt.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

[PATCH 2/3] Change wait_on_bit*() to take an unsigned long*, not a void*

[Palmer Dabbelt]

The implementations of wait_on_bit*() will only work with long-aligned
memory on systems that don't support misaligned loads and stores.
This patch changes the function prototypes to ensure that the compiler
will enforce alignment.

Running

  make defconfig
  make KFLAGS="-Werror"

seems to indicate that, as of c56fb6564dcd ("Fix a misaligned load
inside ptrace_attach()"), there are now no users of non-long-aligned
calls to wait_on_bit*().  I additionally tried a few "make randconfig"
attempts, none of which failed to compile for this reason.

Reviewed-by: Chris Metcalf <cmetcalf@ezchip.com>
Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
---
 include/linux/wait.h | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/include/linux/wait.h b/include/linux/wait.h
index 2db83349865b..d69ac4ecc88b 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -969,7 +969,7 @@ extern int bit_wait_io_timeout(struct wait_bit_key *);
  * on that signal.
  */
 static inline int
-wait_on_bit(void *word, int bit, unsigned mode)
+wait_on_bit(unsigned long *word, int bit, unsigned mode)
 {
 	might_sleep();
 	if (!test_bit(bit, word))
@@ -994,7 +994,7 @@ wait_on_bit(void *word, int bit, unsigned mode)
  * on that signal.
  */
 static inline int
-wait_on_bit_io(void *word, int bit, unsigned mode)
+wait_on_bit_io(unsigned long *word, int bit, unsigned mode)
 {
 	might_sleep();
 	if (!test_bit(bit, word))
@@ -1020,7 +1020,8 @@ wait_on_bit_io(void *word, int bit, unsigned mode)
  * received a signal and the mode permitted wakeup on that signal.
  */
 static inline int
-wait_on_bit_timeout(void *word, int bit, unsigned mode, unsigned long timeout)
+wait_on_bit_timeout(unsigned long *word, int bit, unsigned mode,
+		    unsigned long timeout)
 {
 	might_sleep();
 	if (!test_bit(bit, word))
@@ -1047,7 +1048,8 @@ wait_on_bit_timeout(void *word, int bit, unsigned mode, unsigned long timeout)
  * on that signal.
  */
 static inline int
-wait_on_bit_action(void *word, int bit, wait_bit_action_f *action, unsigned mode)
+wait_on_bit_action(unsigned long *word, int bit, wait_bit_action_f *action,
+		   unsigned mode)
 {
 	might_sleep();
 	if (!test_bit(bit, word))
@@ -1075,7 +1077,7 @@ wait_on_bit_action(void *word, int bit, wait_bit_action_f *action, unsigned mode
  * the @mode allows that signal to wake the process.
  */
 static inline int
-wait_on_bit_lock(void *word, int bit, unsigned mode)
+wait_on_bit_lock(unsigned long *word, int bit, unsigned mode)
 {
 	might_sleep();
 	if (!test_and_set_bit(bit, word))
@@ -1099,7 +1101,7 @@ wait_on_bit_lock(void *word, int bit, unsigned mode)
  * the @mode allows that signal to wake the process.
  */
 static inline int
-wait_on_bit_lock_io(void *word, int bit, unsigned mode)
+wait_on_bit_lock_io(unsigned long *word, int bit, unsigned mode)
 {
 	might_sleep();
 	if (!test_and_set_bit(bit, word))
@@ -1125,7 +1127,8 @@ wait_on_bit_lock_io(void *word, int bit, unsigned mode)
  * the @mode allows that signal to wake the process.
  */
 static inline int
-wait_on_bit_lock_action(void *word, int bit, wait_bit_action_f *action, unsigned mode)
+wait_on_bit_lock_action(unsigned long *word, int bit, wait_bit_action_f *action,
+			unsigned mode)
 {
 	might_sleep();
 	if (!test_and_set_bit(bit, word))
-- 
2.0.5

[PATCH 3/3] Change all uses of JOBCTL_* from int to long

[Palmer Dabbelt]

c56fb6564dcd ("Fix a misaligned load inside ptrace_attach()") makes
jobctl an "unsigned long".  It makes sense to have the masks applied
to it match that type.  This is currently just a cosmetic change, but
it will prevent the mask from being unexpectedly truncated if we ever
end up with masks with more bits.

One instance of "signr" is an int, but I left this alone because the
mask ensures that it will never overflow.

Reviewed-by: Chris Metcalf <cmetcalf@ezchip.com>
Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
---
 include/linux/sched.h | 18 +++++++++---------
 kernel/signal.c       |  6 +++---
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 391827db0a2d..9251155bf27f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2077,22 +2077,22 @@ TASK_PFA_CLEAR(SPREAD_SLAB, spread_slab)
 #define JOBCTL_TRAPPING_BIT	21	/* switching to TRACED */
 #define JOBCTL_LISTENING_BIT	22	/* ptracer is listening for events */
 
-#define JOBCTL_STOP_DEQUEUED	(1 << JOBCTL_STOP_DEQUEUED_BIT)
-#define JOBCTL_STOP_PENDING	(1 << JOBCTL_STOP_PENDING_BIT)
-#define JOBCTL_STOP_CONSUME	(1 << JOBCTL_STOP_CONSUME_BIT)
-#define JOBCTL_TRAP_STOP	(1 << JOBCTL_TRAP_STOP_BIT)
-#define JOBCTL_TRAP_NOTIFY	(1 << JOBCTL_TRAP_NOTIFY_BIT)
-#define JOBCTL_TRAPPING		(1 << JOBCTL_TRAPPING_BIT)
-#define JOBCTL_LISTENING	(1 << JOBCTL_LISTENING_BIT)
+#define JOBCTL_STOP_DEQUEUED	(1UL << JOBCTL_STOP_DEQUEUED_BIT)
+#define JOBCTL_STOP_PENDING	(1UL << JOBCTL_STOP_PENDING_BIT)
+#define JOBCTL_STOP_CONSUME	(1UL << JOBCTL_STOP_CONSUME_BIT)
+#define JOBCTL_TRAP_STOP	(1UL << JOBCTL_TRAP_STOP_BIT)
+#define JOBCTL_TRAP_NOTIFY	(1UL << JOBCTL_TRAP_NOTIFY_BIT)
+#define JOBCTL_TRAPPING		(1UL << JOBCTL_TRAPPING_BIT)
+#define JOBCTL_LISTENING	(1UL << JOBCTL_LISTENING_BIT)
 
 #define JOBCTL_TRAP_MASK	(JOBCTL_TRAP_STOP | JOBCTL_TRAP_NOTIFY)
 #define JOBCTL_PENDING_MASK	(JOBCTL_STOP_PENDING | JOBCTL_TRAP_MASK)
 
 extern bool task_set_jobctl_pending(struct task_struct *task,
-				    unsigned int mask);
+				    unsigned long mask);
 extern void task_clear_jobctl_trapping(struct task_struct *task);
 extern void task_clear_jobctl_pending(struct task_struct *task,
-				      unsigned int mask);
+				      unsigned long mask);
 
 static inline void rcu_copy_process(struct task_struct *p)
 {
diff --git a/kernel/signal.c b/kernel/signal.c
index d51c5ddd855c..f19833b5db3c 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -245,7 +245,7 @@ static inline void print_dropped_signal(int sig)
  * RETURNS:
  * %true if @mask is set, %false if made noop because @task was dying.
  */
-bool task_set_jobctl_pending(struct task_struct *task, unsigned int mask)
+bool task_set_jobctl_pending(struct task_struct *task, unsigned long mask)
 {
 	BUG_ON(mask & ~(JOBCTL_PENDING_MASK | JOBCTL_STOP_CONSUME |
 			JOBCTL_STOP_SIGMASK | JOBCTL_TRAPPING));
@@ -297,7 +297,7 @@ void task_clear_jobctl_trapping(struct task_struct *task)
  * CONTEXT:
  * Must be called with @task->sighand->siglock held.
  */
-void task_clear_jobctl_pending(struct task_struct *task, unsigned int mask)
+void task_clear_jobctl_pending(struct task_struct *task, unsigned long mask)
 {
 	BUG_ON(mask & ~JOBCTL_PENDING_MASK);
 
@@ -2000,7 +2000,7 @@ static bool do_signal_stop(int signr)
 	struct signal_struct *sig = current->signal;
 
 	if (!(current->jobctl & JOBCTL_STOP_PENDING)) {
-		unsigned int gstop = JOBCTL_STOP_PENDING | JOBCTL_STOP_CONSUME;
+		unsigned long gstop = JOBCTL_STOP_PENDING | JOBCTL_STOP_CONSUME;
 		struct task_struct *t;
 
 		/* signr will be recorded in task->jobctl for retries */
-- 
2.0.5

Re: [PATCH 0/3] Fix a misaligned load inside ptrace_attach()

[Peter Zijlstra]

On Thu, Apr 30, 2015 at 09:19:54PM -0700, Palmer Dabbelt wrote:
> I ran across what I believe is a bug in some asm-generic code while
> working on the RISC-V Linux port.  Essentially the problem is that
> wait_on_bit() takes a void *, but then perfroms long-aligned
> operation.  As far as I can tell, this bug could manifest on any other
> architecture that doesn't support misaligned operations and uses this
> particular asm-generic implementation.
> 
> The patch set is split into three parts:
> 
> * #1 fixes the bug by making task_struct.jobctl an unsigned long,
>    which ensures wait_on_bit() always ends up with a long-aligned
>    argument.
> 
> * #2 changes the prototype of wait_on_bit() and friends to take a
>    "unsigned long *" instead of a "void *", with the intent of
>    ensuring these problems don't happen again.
> 
> * #3 is a bit more intrusive: it goes and changes all uses of
>    task_struct.jobctl from int to long.
> 
> I'm not sure if #3 has gone too far, but I think #1 and #2 are sane.
> The cost is making task_struct larger on machines where
> sizeof(long)>sizeof(int), but since it's so big already this isn't too
> much cost.  I thought about making test_bit() perform byte-aligned
> accesses to avoid this cost, but since there are very similar looking
> atomic functions I thought that would be too odd.

Fair enough. Thanks!

[tip:sched/core] signals, sched: Change all uses of JOBCTL_* from 'int' to 'long'

[tip-bot for Palmer Dabbelt]

Commit-ID:  b76808e6808e34e7e78131d2b8cb0535622b8e9f
Gitweb:     http://git.kernel.org/tip/b76808e6808e34e7e78131d2b8cb0535622b8e9f
Author:     Palmer Dabbelt <palmer@dabbelt.com>
AuthorDate: Thu, 30 Apr 2015 21:19:57 -0700
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 8 May 2015 12:04:36 +0200

signals, sched: Change all uses of JOBCTL_* from 'int' to 'long'

c56fb6564dcd ("Fix a misaligned load inside ptrace_attach()") makes
jobctl an "unsigned long".  It makes sense to have the masks applied
to it match that type.  This is currently just a cosmetic change, but
it will prevent the mask from being unexpectedly truncated if we ever
end up with masks with more bits.

One instance of "signr" is an int, but I left this alone because the
mask ensures that it will never overflow.

Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bobby.prani@gmail.com
Cc: oleg@redhat.com
Cc: paulmck@linux.vnet.ibm.com
Cc: richard@nod.at
Cc: vdavydov@parallels.com
Link: http://lkml.kernel.org/r/1430453997-32459-4-git-send-email-palmer@dabbelt.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 include/linux/sched.h | 18 +++++++++---------
 kernel/signal.c       |  6 +++---
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 85cf253..4f066cb 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2082,22 +2082,22 @@ TASK_PFA_CLEAR(SPREAD_SLAB, spread_slab)
 #define JOBCTL_TRAPPING_BIT	21	/* switching to TRACED */
 #define JOBCTL_LISTENING_BIT	22	/* ptracer is listening for events */
 
-#define JOBCTL_STOP_DEQUEUED	(1 << JOBCTL_STOP_DEQUEUED_BIT)
-#define JOBCTL_STOP_PENDING	(1 << JOBCTL_STOP_PENDING_BIT)
-#define JOBCTL_STOP_CONSUME	(1 << JOBCTL_STOP_CONSUME_BIT)
-#define JOBCTL_TRAP_STOP	(1 << JOBCTL_TRAP_STOP_BIT)
-#define JOBCTL_TRAP_NOTIFY	(1 << JOBCTL_TRAP_NOTIFY_BIT)
-#define JOBCTL_TRAPPING		(1 << JOBCTL_TRAPPING_BIT)
-#define JOBCTL_LISTENING	(1 << JOBCTL_LISTENING_BIT)
+#define JOBCTL_STOP_DEQUEUED	(1UL << JOBCTL_STOP_DEQUEUED_BIT)
+#define JOBCTL_STOP_PENDING	(1UL << JOBCTL_STOP_PENDING_BIT)
+#define JOBCTL_STOP_CONSUME	(1UL << JOBCTL_STOP_CONSUME_BIT)
+#define JOBCTL_TRAP_STOP	(1UL << JOBCTL_TRAP_STOP_BIT)
+#define JOBCTL_TRAP_NOTIFY	(1UL << JOBCTL_TRAP_NOTIFY_BIT)
+#define JOBCTL_TRAPPING		(1UL << JOBCTL_TRAPPING_BIT)
+#define JOBCTL_LISTENING	(1UL << JOBCTL_LISTENING_BIT)
 
 #define JOBCTL_TRAP_MASK	(JOBCTL_TRAP_STOP | JOBCTL_TRAP_NOTIFY)
 #define JOBCTL_PENDING_MASK	(JOBCTL_STOP_PENDING | JOBCTL_TRAP_MASK)
 
 extern bool task_set_jobctl_pending(struct task_struct *task,
-				    unsigned int mask);
+				    unsigned long mask);
 extern void task_clear_jobctl_trapping(struct task_struct *task);
 extern void task_clear_jobctl_pending(struct task_struct *task,
-				      unsigned int mask);
+				      unsigned long mask);
 
 static inline void rcu_copy_process(struct task_struct *p)
 {
diff --git a/kernel/signal.c b/kernel/signal.c
index d51c5dd..f19833b 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -245,7 +245,7 @@ static inline void print_dropped_signal(int sig)
  * RETURNS:
  * %true if @mask is set, %false if made noop because @task was dying.
  */
-bool task_set_jobctl_pending(struct task_struct *task, unsigned int mask)
+bool task_set_jobctl_pending(struct task_struct *task, unsigned long mask)
 {
 	BUG_ON(mask & ~(JOBCTL_PENDING_MASK | JOBCTL_STOP_CONSUME |
 			JOBCTL_STOP_SIGMASK | JOBCTL_TRAPPING));
@@ -297,7 +297,7 @@ void task_clear_jobctl_trapping(struct task_struct *task)
  * CONTEXT:
  * Must be called with @task->sighand->siglock held.
  */
-void task_clear_jobctl_pending(struct task_struct *task, unsigned int mask)
+void task_clear_jobctl_pending(struct task_struct *task, unsigned long mask)
 {
 	BUG_ON(mask & ~JOBCTL_PENDING_MASK);
 
@@ -2000,7 +2000,7 @@ static bool do_signal_stop(int signr)
 	struct signal_struct *sig = current->signal;
 
 	if (!(current->jobctl & JOBCTL_STOP_PENDING)) {
-		unsigned int gstop = JOBCTL_STOP_PENDING | JOBCTL_STOP_CONSUME;
+		unsigned long gstop = JOBCTL_STOP_PENDING | JOBCTL_STOP_CONSUME;
 		struct task_struct *t;
 
 		/* signr will be recorded in task->jobctl for retries */

[tip:sched/core] sched/wait: Change wait_on_bit*() to take an unsigned long *, not a void *

[tip-bot for Palmer Dabbelt]

Commit-ID:  7e60598785f30cf3dc9e476cc0fc3feeb37a0c63
Gitweb:     http://git.kernel.org/tip/7e60598785f30cf3dc9e476cc0fc3feeb37a0c63
Author:     Palmer Dabbelt <palmer@dabbelt.com>
AuthorDate: Thu, 30 Apr 2015 21:19:56 -0700
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 8 May 2015 12:05:41 +0200

sched/wait: Change wait_on_bit*() to take an unsigned long *, not a void *

The implementations of wait_on_bit*() will only work with long-aligned
memory on systems that don't support misaligned loads and stores.

This patch changes the function prototypes to ensure that the compiler
will enforce alignment.

Running

  make defconfig
  make KFLAGS="-Werror"

seems to indicate that, as of c56fb6564dcd ("Fix a misaligned load
inside ptrace_attach()"), there are now no users of non-long-aligned
calls to wait_on_bit*().  I additionally tried a few "make randconfig"
attempts, none of which failed to compile for this reason.

Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bobby.prani@gmail.com
Cc: oleg@redhat.com
Cc: paulmck@linux.vnet.ibm.com
Cc: richard@nod.at
Cc: vdavydov@parallels.com
Link: http://lkml.kernel.org/r/1430453997-32459-3-git-send-email-palmer@dabbelt.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 include/linux/wait.h | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/include/linux/wait.h b/include/linux/wait.h
index 2db8334..d69ac4e 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -969,7 +969,7 @@ extern int bit_wait_io_timeout(struct wait_bit_key *);
  * on that signal.
  */
 static inline int
-wait_on_bit(void *word, int bit, unsigned mode)
+wait_on_bit(unsigned long *word, int bit, unsigned mode)
 {
 	might_sleep();
 	if (!test_bit(bit, word))
@@ -994,7 +994,7 @@ wait_on_bit(void *word, int bit, unsigned mode)
  * on that signal.
  */
 static inline int
-wait_on_bit_io(void *word, int bit, unsigned mode)
+wait_on_bit_io(unsigned long *word, int bit, unsigned mode)
 {
 	might_sleep();
 	if (!test_bit(bit, word))
@@ -1020,7 +1020,8 @@ wait_on_bit_io(void *word, int bit, unsigned mode)
  * received a signal and the mode permitted wakeup on that signal.
  */
 static inline int
-wait_on_bit_timeout(void *word, int bit, unsigned mode, unsigned long timeout)
+wait_on_bit_timeout(unsigned long *word, int bit, unsigned mode,
+		    unsigned long timeout)
 {
 	might_sleep();
 	if (!test_bit(bit, word))
@@ -1047,7 +1048,8 @@ wait_on_bit_timeout(void *word, int bit, unsigned mode, unsigned long timeout)
  * on that signal.
  */
 static inline int
-wait_on_bit_action(void *word, int bit, wait_bit_action_f *action, unsigned mode)
+wait_on_bit_action(unsigned long *word, int bit, wait_bit_action_f *action,
+		   unsigned mode)
 {
 	might_sleep();
 	if (!test_bit(bit, word))
@@ -1075,7 +1077,7 @@ wait_on_bit_action(void *word, int bit, wait_bit_action_f *action, unsigned mode
  * the @mode allows that signal to wake the process.
  */
 static inline int
-wait_on_bit_lock(void *word, int bit, unsigned mode)
+wait_on_bit_lock(unsigned long *word, int bit, unsigned mode)
 {
 	might_sleep();
 	if (!test_and_set_bit(bit, word))
@@ -1099,7 +1101,7 @@ wait_on_bit_lock(void *word, int bit, unsigned mode)
  * the @mode allows that signal to wake the process.
  */
 static inline int
-wait_on_bit_lock_io(void *word, int bit, unsigned mode)
+wait_on_bit_lock_io(unsigned long *word, int bit, unsigned mode)
 {
 	might_sleep();
 	if (!test_and_set_bit(bit, word))
@@ -1125,7 +1127,8 @@ wait_on_bit_lock_io(void *word, int bit, unsigned mode)
  * the @mode allows that signal to wake the process.
  */
 static inline int
-wait_on_bit_lock_action(void *word, int bit, wait_bit_action_f *action, unsigned mode)
+wait_on_bit_lock_action(unsigned long *word, int bit, wait_bit_action_f *action,
+			unsigned mode)
 {
 	might_sleep();
 	if (!test_and_set_bit(bit, word))

[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@dabbelt.com>
AuthorDate: Thu, 30 Apr 2015 21:19:55 -0700
Committer:  Ingo Molnar <mingo@kernel.org>
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@dabbelt.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bobby.prani@gmail.com
Cc: oleg@redhat.com
Cc: paulmck@linux.vnet.ibm.com
Cc: richard@nod.at
Cc: vdavydov@parallels.com
Link: http://lkml.kernel.org/r/1430453997-32459-2-git-send-email-palmer@dabbelt.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 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;