diff options
authorLinus Torvalds <torvalds@linux-foundation.org>2017-12-27 13:06:57 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-12-27 13:06:57 -0800
commit5f520fc318764df800789edd202b5e3b55130613 (patch)
parent9b9577948f64edc1c967d80deb6910c811abb8fc (diff)
parent4397f04575c44e1440ec2e49b6302785c95fd2f8 (diff)
Merge tag 'trace-v4.15-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing fixes from Steven Rostedt: "While doing tests on tracing over the network, I found that the packets were getting corrupted. In the process I found three bugs. One was the culprit, but the other two scared me. After deeper investigation, they were not as major as I thought they were, due to a signed compared to an unsigned that prevented a negative number from doing actual harm. The two bigger bugs: - Mask the ring buffer data page length. There are data flags at the high bits of the length field. These were not cleared via the length function, and the length could return a negative number. (Although the number returned was unsigned, but was assigned to a signed number) Luckily, this value was compared to PAGE_SIZE which is unsigned and kept it from entering the path that could have caused damage. - Check the page usage before reusing the ring buffer reader page. TCP increments the page ref when passing the page off to the network. The page is passed back to the ring buffer for use on free. But the page could still be in use by the TCP stack. Minor bugs: - Related to the first bug. No need to clear out the unused ring buffer data before sending to user space. It is now done by the ring buffer code itself. - Reset pointers after free on error path. There were some cases in the error path that pointers were freed but not set to NULL, and could have them freed again, having a pointer freed twice" * tag 'trace-v4.15-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: tracing: Fix possible double free on failure of allocating trace buffer tracing: Fix crash when it fails to alloc ring buffer ring-buffer: Do no reuse reader page if still in use tracing: Remove extra zeroing out of the ring buffer page ring-buffer: Mask out the info bits when returning buffer page length
2 files changed, 15 insertions, 10 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index c87766c1c204..9ab18995ff1e 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -280,6 +280,8 @@ EXPORT_SYMBOL_GPL(ring_buffer_event_data);
/* Missed count stored at end */
#define RB_MISSED_STORED (1 << 30)
struct buffer_data_page {
u64 time_stamp; /* page time stamp */
local_t commit; /* write committed index */
@@ -331,7 +333,9 @@ static void rb_init_page(struct buffer_data_page *bpage)
size_t ring_buffer_page_len(void *page)
- return local_read(&((struct buffer_data_page *)page)->commit)
+ struct buffer_data_page *bpage = page;
+ return (local_read(&bpage->commit) & ~RB_MISSED_FLAGS)
@@ -4400,8 +4404,13 @@ void ring_buffer_free_read_page(struct ring_buffer *buffer, int cpu, void *data)
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
struct buffer_data_page *bpage = data;
+ struct page *page = virt_to_page(bpage);
unsigned long flags;
+ /* If the page is still in use someplace else, we can't reuse it */
+ if (page_ref_count(page) > 1)
+ goto out;
@@ -4413,6 +4422,7 @@ void ring_buffer_free_read_page(struct ring_buffer *buffer, int cpu, void *data)
+ out:
free_page((unsigned long)bpage);
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 59518b8126d0..2a8d8a294345 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6769,7 +6769,7 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
.spd_release = buffer_spd_release,
struct buffer_ref *ref;
- int entries, size, i;
+ int entries, i;
ssize_t ret = 0;
@@ -6823,14 +6823,6 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
- /*
- * zero out any left over data, this is going to
- * user land.
- */
- size = ring_buffer_page_len(ref->page);
- if (size < PAGE_SIZE)
- memset(ref->page + size, 0, PAGE_SIZE - size);
page = virt_to_page(ref->page);
spd.pages[i] = page;
@@ -7588,6 +7580,7 @@ allocate_trace_buffer(struct trace_array *tr, struct trace_buffer *buf, int size
buf->data = alloc_percpu(struct trace_array_cpu);
if (!buf->data) {
+ buf->buffer = NULL;
return -ENOMEM;
@@ -7611,7 +7604,9 @@ static int allocate_trace_buffers(struct trace_array *tr, int size)
allocate_snapshot ? size : 1);
if (WARN_ON(ret)) {
+ tr->trace_buffer.buffer = NULL;
+ tr->trace_buffer.data = NULL;
return -ENOMEM;
tr->allocated_snapshot = allocate_snapshot;

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