From 1ca1a4cf59ea343a1a70084fe7cc96f37f3cf5b1 Mon Sep 17 00:00:00 2001 From: Chris Metcalf Date: Thu, 14 Nov 2013 12:09:21 -0500 Subject: [PATCH] connector: improved unaligned access error fix In af3e095a1fb4, 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: Chris Metcalf Signed-off-by: David S. Miller --- drivers/connector/cn_proc.c | 72 +++++++++++++++++++++---------------- 1 file changed, 42 insertions(+), 30 deletions(-) diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c index c73fc2b74de2..18c5b9b16645 100644 --- a/drivers/connector/cn_proc.c +++ b/drivers/connector/cn_proc.c @@ -32,11 +32,23 @@ #include #include -#include - #include -#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; -- 2.30.2