[for-next][PATCH 0/3] tracing: Fixes for 4.13-rc3

[for-next][PATCH 0/3] tracing: Fixes for 4.13-rc3

[Steven Rostedt]

  git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
for-next

Head SHA1: a7e52ad7ed82e21273eccff93d1477a7b313aabb


Dan Carpenter (1):
      tracing: Missing error code in tracer_alloc_buffers()

Steven Rostedt (VMware) (2):
      tracing: Call clear_boot_tracer() at lateinit_sync
      ring-buffer: Have ring_buffer_alloc_read_page() return error on offline CPU

----
 kernel/trace/ring_buffer.c           | 14 +++++++++-----
 kernel/trace/ring_buffer_benchmark.c |  2 +-
 kernel/trace/trace.c                 | 19 +++++++++++++------
 3 files changed, 23 insertions(+), 12 deletions(-)

[for-next][PATCH 1/3] tracing: Call clear_boot_tracer() at lateinit_sync

[Steven Rostedt]

[-- Attachment #1: 0001-tracing-Call-clear_boot_tracer-at-lateinit_sync.patch --]
[-- Type: text/plain, Size: 1334 bytes --]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

The clear_boot_tracer function is used to reset the default_bootup_tracer
string to prevent it from being accessed after boot, as it originally points
to init data. But since clear_boot_tracer() is called via the
init_lateinit() call, it races with the initcall for registering the hwlat
tracer. If someone adds "ftrace=hwlat" to the kernel command line, depending
on how the linker sets up the text, the saved command line may be cleared,
and the hwlat tracer never is initialized.

Simply have the clear_boot_tracer() be called by initcall_lateinit_sync() as
that's for tasks to be called after lateinit.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=196551

Cc: stable@vger.kernel.org
Fixes: e7c15cd8a ("tracing: Added hardware latency tracer")
Reported-by: Zamir SUN <sztsian@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/trace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 42b9355033d4..784fb43b2abe 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -8407,4 +8407,4 @@ __init static int clear_boot_tracer(void)
 }
 
 fs_initcall(tracer_init_tracefs);
-late_initcall(clear_boot_tracer);
+late_initcall_sync(clear_boot_tracer);
-- 
2.13.2

[for-next][PATCH 2/3] tracing: Missing error code in tracer_alloc_buffers()

[Steven Rostedt]

[-- Attachment #1: 0002-tracing-Missing-error-code-in-tracer_alloc_buffers.patch --]
[-- Type: text/plain, Size: 1051 bytes --]

From: Dan Carpenter <dan.carpenter@oracle.com>

If ring_buffer_alloc() or one of the next couple function calls fail
then we should return -ENOMEM but the current code returns success.

Link: http://lkml.kernel.org/r/20170801110201.ajdkct7vwzixahvx@mwanda

Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: stable@vger.kernel.org
Fixes: b32614c03413 ('tracing/rb: Convert to hotplug state machine')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/trace.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 784fb43b2abe..d815fc317e9d 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -8293,6 +8293,7 @@ __init static int tracer_alloc_buffers(void)
 	if (ret < 0)
 		goto out_free_cpumask;
 	/* Used for event triggers */
+	ret = -ENOMEM;
 	temp_buffer = ring_buffer_alloc(PAGE_SIZE, RB_FL_OVERWRITE);
 	if (!temp_buffer)
 		goto out_rm_hp_state;
-- 
2.13.2

[for-next][PATCH 3/3] ring-buffer: Have ring_buffer_alloc_read_page() return error on offline CPU

[Steven Rostedt]

[-- Attachment #1: 0003-ring-buffer-Have-ring_buffer_alloc_read_page-return-.patch --]
[-- Type: text/plain, Size: 5390 bytes --]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

Chunyu Hu reported:
  "per_cpu trace directories and files are created for all possible cpus,
   but only the cpus which have ever been on-lined have their own per cpu
   ring buffer (allocated by cpuhp threads). While trace_buffers_open, the
   open handler for trace file 'trace_pipe_raw' is always trying to access
   field of ring_buffer_per_cpu, and would panic with the NULL pointer.

   Align the behavior of trace_pipe_raw with trace_pipe, that returns -NODEV
   when openning it if that cpu does not have trace ring buffer.

   Reproduce:
   cat /sys/kernel/debug/tracing/per_cpu/cpu31/trace_pipe_raw
   (cpu31 is never on-lined, this is a 16 cores x86_64 box)

   Tested with:
   1) boot with maxcpus=14, read trace_pipe_raw of cpu15.
      Got -NODEV.
   2) oneline cpu15, read trace_pipe_raw of cpu15.
      Get the raw trace data.

   Call trace:
   [ 5760.950995] RIP: 0010:ring_buffer_alloc_read_page+0x32/0xe0
   [ 5760.961678]  tracing_buffers_read+0x1f6/0x230
   [ 5760.962695]  __vfs_read+0x37/0x160
   [ 5760.963498]  ? __vfs_read+0x5/0x160
   [ 5760.964339]  ? security_file_permission+0x9d/0xc0
   [ 5760.965451]  ? __vfs_read+0x5/0x160
   [ 5760.966280]  vfs_read+0x8c/0x130
   [ 5760.967070]  SyS_read+0x55/0xc0
   [ 5760.967779]  do_syscall_64+0x67/0x150
   [ 5760.968687]  entry_SYSCALL64_slow_path+0x25/0x25"

This was introduced by the addition of the feature to reuse reader pages
instead of re-allocating them. The problem is that the allocation of a
reader page (which is per cpu) does not check if the cpu is online and set
up for the ring buffer.

Link: http://lkml.kernel.org/r/1500880866-1177-1-git-send-email-chuhu@redhat.com

Cc: stable@vger.kernel.org
Fixes: 73a757e63114 ("ring-buffer: Return reader page back into existing ring buffer")
Reported-by: Chunyu Hu <chuhu@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer.c           | 14 +++++++++-----
 kernel/trace/ring_buffer_benchmark.c |  2 +-
 kernel/trace/trace.c                 | 16 +++++++++++-----
 3 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 529cc50d7243..81279c6602ff 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -4386,15 +4386,19 @@ EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
  * the page that was allocated, with the read page of the buffer.
  *
  * Returns:
- *  The page allocated, or NULL on error.
+ *  The page allocated, or ERR_PTR
  */
 void *ring_buffer_alloc_read_page(struct ring_buffer *buffer, int cpu)
 {
-	struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
+	struct ring_buffer_per_cpu *cpu_buffer;
 	struct buffer_data_page *bpage = NULL;
 	unsigned long flags;
 	struct page *page;
 
+	if (!cpumask_test_cpu(cpu, buffer->cpumask))
+		return ERR_PTR(-ENODEV);
+
+	cpu_buffer = buffer->buffers[cpu];
 	local_irq_save(flags);
 	arch_spin_lock(&cpu_buffer->lock);
 
@@ -4412,7 +4416,7 @@ void *ring_buffer_alloc_read_page(struct ring_buffer *buffer, int cpu)
 	page = alloc_pages_node(cpu_to_node(cpu),
 				GFP_KERNEL | __GFP_NORETRY, 0);
 	if (!page)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	bpage = page_address(page);
 
@@ -4467,8 +4471,8 @@ EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
  *
  * for example:
  *	rpage = ring_buffer_alloc_read_page(buffer, cpu);
- *	if (!rpage)
- *		return error;
+ *	if (IS_ERR(rpage))
+ *		return PTR_ERR(rpage);
  *	ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
  *	if (ret >= 0)
  *		process_page(rpage, ret);
diff --git a/kernel/trace/ring_buffer_benchmark.c b/kernel/trace/ring_buffer_benchmark.c
index 9fbcaf567886..68ee79afe31c 100644
--- a/kernel/trace/ring_buffer_benchmark.c
+++ b/kernel/trace/ring_buffer_benchmark.c
@@ -113,7 +113,7 @@ static enum event_status read_page(int cpu)
 	int i;
 
 	bpage = ring_buffer_alloc_read_page(buffer, cpu);
-	if (!bpage)
+	if (IS_ERR(bpage))
 		return EVENT_DROPPED;
 
 	ret = ring_buffer_read_page(buffer, &bpage, PAGE_SIZE, cpu, 1);
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index d815fc317e9d..44004d8aa3b3 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6598,7 +6598,7 @@ tracing_buffers_read(struct file *filp, char __user *ubuf,
 {
 	struct ftrace_buffer_info *info = filp->private_data;
 	struct trace_iterator *iter = &info->iter;
-	ssize_t ret;
+	ssize_t ret = 0;
 	ssize_t size;
 
 	if (!count)
@@ -6612,10 +6612,15 @@ tracing_buffers_read(struct file *filp, char __user *ubuf,
 	if (!info->spare) {
 		info->spare = ring_buffer_alloc_read_page(iter->trace_buffer->buffer,
 							  iter->cpu_file);
-		info->spare_cpu = iter->cpu_file;
+		if (IS_ERR(info->spare)) {
+			ret = PTR_ERR(info->spare);
+			info->spare = NULL;
+		} else {
+			info->spare_cpu = iter->cpu_file;
+		}
 	}
 	if (!info->spare)
-		return -ENOMEM;
+		return ret;
 
 	/* Do we have previous read data to read? */
 	if (info->read < PAGE_SIZE)
@@ -6790,8 +6795,9 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
 		ref->ref = 1;
 		ref->buffer = iter->trace_buffer->buffer;
 		ref->page = ring_buffer_alloc_read_page(ref->buffer, iter->cpu_file);
-		if (!ref->page) {
-			ret = -ENOMEM;
+		if (IS_ERR(ref->page)) {
+			ret = PTR_ERR(ref->page);
+			ref->page = NULL;
 			kfree(ref);
 			break;
 		}
-- 
2.13.2