Commit 1ca1a4cf authored by Chris Metcalf's avatar Chris Metcalf Committed by David S. Miller
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connector: improved unaligned access error fix 



In af3e095a, Erik Jacobsen fixed one type of unaligned access
bug for ia64 by converting a 64-bit write to use put_unaligned().
Unfortunately, since gcc will convert a short memset() to a series
of appropriately-aligned stores, the problem is now visible again
on tilegx, where the memset that zeros out proc_event is converted
to three 64-bit stores, causing an unaligned access panic.

A better fix for the original problem is to ensure that proc_event
is aligned to 8 bytes here.  We can do that relatively easily by
arranging to start the struct cn_msg aligned to 8 bytes and then
offset by 4 bytes.  Doing so means that the immediately following
proc_event structure is then correctly aligned to 8 bytes.

The result is that the memset() stores are now aligned, and as an
added benefit, we can remove the put_unaligned() calls in the code.

Signed-off-by: default avatarChris Metcalf <cmetcalf@tilera.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 2abc2f07

drivers/connector/cn_proc.c

+42 −30
Original line number Diff line number Diff line
@@ -32,11 +32,23 @@ 
#include <linux/atomic.h>

#include <linux/pid_namespace.h>



#include <asm/unaligned.h>



#include <linux/cn_proc.h>



#define CN_PROC_MSG_SIZE (sizeof(struct cn_msg) + sizeof(struct proc_event))

/*

 * Size of a cn_msg followed by a proc_event structure.  Since the

 * sizeof struct cn_msg is a multiple of 4 bytes, but not 8 bytes, we

 * add one 4-byte word to the size here, and then start the actual

 * cn_msg structure 4 bytes into the stack buffer.  The result is that

 * the immediately following proc_event structure is aligned to 8 bytes.

 */

#define CN_PROC_MSG_SIZE (sizeof(struct cn_msg) + sizeof(struct proc_event) + 4)



/* See comment above; we test our assumption about sizeof struct cn_msg here. */

static inline struct cn_msg *buffer_to_cn_msg(__u8 *buffer)

{

	BUILD_BUG_ON(sizeof(struct cn_msg) != 20);

	return (struct cn_msg *)(buffer + 4);

}



static atomic_t proc_event_num_listeners = ATOMIC_INIT(0);

static struct cb_id cn_proc_event_id = { CN_IDX_PROC, CN_VAL_PROC };
@@ -56,19 +68,19 @@ void proc_fork_connector(struct task_struct *task) 
{

	struct cn_msg *msg;

	struct proc_event *ev;

	__u8 buffer[CN_PROC_MSG_SIZE];

	__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);

	struct timespec ts;

	struct task_struct *parent;



	if (atomic_read(&proc_event_num_listeners) < 1)

		return;



	msg = (struct cn_msg *)buffer;

	msg = buffer_to_cn_msg(buffer);

	ev = (struct proc_event *)msg->data;

	memset(&ev->event_data, 0, sizeof(ev->event_data));

	get_seq(&msg->seq, &ev->cpu);

	ktime_get_ts(&ts); /* get high res monotonic timestamp */

	put_unaligned(timespec_to_ns(&ts), (__u64 *)&ev->timestamp_ns);

	ev->timestamp_ns = timespec_to_ns(&ts);

	ev->what = PROC_EVENT_FORK;

	rcu_read_lock();

	parent = rcu_dereference(task->real_parent);
@@ -91,17 +103,17 @@ void proc_exec_connector(struct task_struct *task) 
	struct cn_msg *msg;

	struct proc_event *ev;

	struct timespec ts;

	__u8 buffer[CN_PROC_MSG_SIZE];

	__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);



	if (atomic_read(&proc_event_num_listeners) < 1)

		return;



	msg = (struct cn_msg *)buffer;

	msg = buffer_to_cn_msg(buffer);

	ev = (struct proc_event *)msg->data;

	memset(&ev->event_data, 0, sizeof(ev->event_data));

	get_seq(&msg->seq, &ev->cpu);

	ktime_get_ts(&ts); /* get high res monotonic timestamp */

	put_unaligned(timespec_to_ns(&ts), (__u64 *)&ev->timestamp_ns);

	ev->timestamp_ns = timespec_to_ns(&ts);

	ev->what = PROC_EVENT_EXEC;

	ev->event_data.exec.process_pid = task->pid;

	ev->event_data.exec.process_tgid = task->tgid;
@@ -117,14 +129,14 @@ void proc_id_connector(struct task_struct *task, int which_id) 
{

	struct cn_msg *msg;

	struct proc_event *ev;

	__u8 buffer[CN_PROC_MSG_SIZE];

	__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);

	struct timespec ts;

	const struct cred *cred;



	if (atomic_read(&proc_event_num_listeners) < 1)

		return;



	msg = (struct cn_msg *)buffer;

	msg = buffer_to_cn_msg(buffer);

	ev = (struct proc_event *)msg->data;

	memset(&ev->event_data, 0, sizeof(ev->event_data));

	ev->what = which_id;
@@ -145,7 +157,7 @@ void proc_id_connector(struct task_struct *task, int which_id) 
	rcu_read_unlock();

	get_seq(&msg->seq, &ev->cpu);

	ktime_get_ts(&ts); /* get high res monotonic timestamp */

	put_unaligned(timespec_to_ns(&ts), (__u64 *)&ev->timestamp_ns);

	ev->timestamp_ns = timespec_to_ns(&ts);



	memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));

	msg->ack = 0; /* not used */
@@ -159,17 +171,17 @@ void proc_sid_connector(struct task_struct *task) 
	struct cn_msg *msg;

	struct proc_event *ev;

	struct timespec ts;

	__u8 buffer[CN_PROC_MSG_SIZE];

	__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);



	if (atomic_read(&proc_event_num_listeners) < 1)

		return;



	msg = (struct cn_msg *)buffer;

	msg = buffer_to_cn_msg(buffer);

	ev = (struct proc_event *)msg->data;

	memset(&ev->event_data, 0, sizeof(ev->event_data));

	get_seq(&msg->seq, &ev->cpu);

	ktime_get_ts(&ts); /* get high res monotonic timestamp */

	put_unaligned(timespec_to_ns(&ts), (__u64 *)&ev->timestamp_ns);

	ev->timestamp_ns = timespec_to_ns(&ts);

	ev->what = PROC_EVENT_SID;

	ev->event_data.sid.process_pid = task->pid;

	ev->event_data.sid.process_tgid = task->tgid;
@@ -186,17 +198,17 @@ void proc_ptrace_connector(struct task_struct *task, int ptrace_id) 
	struct cn_msg *msg;

	struct proc_event *ev;

	struct timespec ts;

	__u8 buffer[CN_PROC_MSG_SIZE];

	__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);



	if (atomic_read(&proc_event_num_listeners) < 1)

		return;



	msg = (struct cn_msg *)buffer;

	msg = buffer_to_cn_msg(buffer);

	ev = (struct proc_event *)msg->data;

	memset(&ev->event_data, 0, sizeof(ev->event_data));

	get_seq(&msg->seq, &ev->cpu);

	ktime_get_ts(&ts); /* get high res monotonic timestamp */

	put_unaligned(timespec_to_ns(&ts), (__u64 *)&ev->timestamp_ns);

	ev->timestamp_ns = timespec_to_ns(&ts);

	ev->what = PROC_EVENT_PTRACE;

	ev->event_data.ptrace.process_pid  = task->pid;

	ev->event_data.ptrace.process_tgid = task->tgid;
@@ -221,17 +233,17 @@ void proc_comm_connector(struct task_struct *task) 
	struct cn_msg *msg;

	struct proc_event *ev;

	struct timespec ts;

	__u8 buffer[CN_PROC_MSG_SIZE];

	__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);



	if (atomic_read(&proc_event_num_listeners) < 1)

		return;



	msg = (struct cn_msg *)buffer;

	msg = buffer_to_cn_msg(buffer);

	ev = (struct proc_event *)msg->data;

	memset(&ev->event_data, 0, sizeof(ev->event_data));

	get_seq(&msg->seq, &ev->cpu);

	ktime_get_ts(&ts); /* get high res monotonic timestamp */

	put_unaligned(timespec_to_ns(&ts), (__u64 *)&ev->timestamp_ns);

	ev->timestamp_ns = timespec_to_ns(&ts);

	ev->what = PROC_EVENT_COMM;

	ev->event_data.comm.process_pid  = task->pid;

	ev->event_data.comm.process_tgid = task->tgid;
@@ -248,18 +260,18 @@ void proc_coredump_connector(struct task_struct *task) 
{

	struct cn_msg *msg;

	struct proc_event *ev;

	__u8 buffer[CN_PROC_MSG_SIZE];

	__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);

	struct timespec ts;



	if (atomic_read(&proc_event_num_listeners) < 1)

		return;



	msg = (struct cn_msg *)buffer;

	msg = buffer_to_cn_msg(buffer);

	ev = (struct proc_event *)msg->data;

	memset(&ev->event_data, 0, sizeof(ev->event_data));

	get_seq(&msg->seq, &ev->cpu);

	ktime_get_ts(&ts); /* get high res monotonic timestamp */

	put_unaligned(timespec_to_ns(&ts), (__u64 *)&ev->timestamp_ns);

	ev->timestamp_ns = timespec_to_ns(&ts);

	ev->what = PROC_EVENT_COREDUMP;

	ev->event_data.coredump.process_pid = task->pid;

	ev->event_data.coredump.process_tgid = task->tgid;
@@ -275,18 +287,18 @@ void proc_exit_connector(struct task_struct *task) 
{

	struct cn_msg *msg;

	struct proc_event *ev;

	__u8 buffer[CN_PROC_MSG_SIZE];

	__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);

	struct timespec ts;



	if (atomic_read(&proc_event_num_listeners) < 1)

		return;



	msg = (struct cn_msg *)buffer;

	msg = buffer_to_cn_msg(buffer);

	ev = (struct proc_event *)msg->data;

	memset(&ev->event_data, 0, sizeof(ev->event_data));

	get_seq(&msg->seq, &ev->cpu);

	ktime_get_ts(&ts); /* get high res monotonic timestamp */

	put_unaligned(timespec_to_ns(&ts), (__u64 *)&ev->timestamp_ns);

	ev->timestamp_ns = timespec_to_ns(&ts);

	ev->what = PROC_EVENT_EXIT;

	ev->event_data.exit.process_pid = task->pid;

	ev->event_data.exit.process_tgid = task->tgid;
@@ -312,18 +324,18 @@ static void cn_proc_ack(int err, int rcvd_seq, int rcvd_ack) 
{

	struct cn_msg *msg;

	struct proc_event *ev;

	__u8 buffer[CN_PROC_MSG_SIZE];

	__u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);

	struct timespec ts;



	if (atomic_read(&proc_event_num_listeners) < 1)

		return;



	msg = (struct cn_msg *)buffer;

	msg = buffer_to_cn_msg(buffer);

	ev = (struct proc_event *)msg->data;

	memset(&ev->event_data, 0, sizeof(ev->event_data));

	msg->seq = rcvd_seq;

	ktime_get_ts(&ts); /* get high res monotonic timestamp */

	put_unaligned(timespec_to_ns(&ts), (__u64 *)&ev->timestamp_ns);

	ev->timestamp_ns = timespec_to_ns(&ts);

	ev->cpu = -1;

	ev->what = PROC_EVENT_NONE;

	ev->event_data.ack.err = err;

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