[PATCH 5.15 090/124] perf/core: Fix perf_mmap fail when CONFIG_PERF_USE_VMALLOC enabled

Greg Kroah-Hartman
2022-04-26T09:12:42Z

From: Zhipeng Xie <xiezhipeng1@huawei.com>

[ Upstream commit 60490e7966659b26d74bf1fa4aa8693d9a94ca88 ]

This problem can be reproduced with CONFIG_PERF_USE_VMALLOC enabled on
both x86_64 and aarch64 arch when using sysdig -B(using ebpf)[1].
sysdig -B works fine after rebuilding the kernel with
CONFIG_PERF_USE_VMALLOC disabled.

I tracked it down to the if condition event->rb->nr_pages != nr_pages
in perf_mmap is true when CONFIG_PERF_USE_VMALLOC is enabled where
event->rb->nr_pages = 1 and nr_pages = 2048 resulting perf_mmap to
return -EINVAL. This is because when CONFIG_PERF_USE_VMALLOC is
enabled, rb->nr_pages is always equal to 1.

Arch with CONFIG_PERF_USE_VMALLOC enabled by default:
arc/arm/csky/mips/sh/sparc/xtensa

Arch with CONFIG_PERF_USE_VMALLOC disabled by default:
x86_64/aarch64/...

Fix this problem by using data_page_nr()

[1] https://github.com/draios/sysdig

Fixes: 906010b2134e ("perf_event: Provide vmalloc() based mmap() backing")
Signed-off-by: Zhipeng Xie <xiezhipeng1@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220209145417.6495-1-xiezhipeng1@huawei.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/events/core.c | 2 +-
kernel/events/internal.h | 5 +++++
kernel/events/ring_buffer.c | 5 -----
3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 699446d60b6b..7c891a8eb323 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6348,7 +6348,7 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
again:
mutex_lock(&event->mmap_mutex);
if (event->rb) {
- if (event->rb->nr_pages != nr_pages) {
+ if (data_page_nr(event->rb) != nr_pages) {
ret = -EINVAL;
goto unlock;
}
diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index 228801e20788..aa23ffdaf819 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -116,6 +116,11 @@ static inline int page_order(struct perf_buffer *rb)
}
#endif

+static inline int data_page_nr(struct perf_buffer *rb)
+{
+ return rb->nr_pages << page_order(rb);
+}
+
static inline unsigned long perf_data_size(struct perf_buffer *rb)
{
return rb->nr_pages << (PAGE_SHIFT + page_order(rb));
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 52868716ec35..fb35b926024c 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -859,11 +859,6 @@ void rb_free(struct perf_buffer *rb)
}

#else
-static int data_page_nr(struct perf_buffer *rb)
-{
- return rb->nr_pages << page_order(rb);
-}
-
static struct page *
__perf_mmap_to_page(struct perf_buffer *rb, unsigned long pgoff)
{
--
2.35.1