[PATCH] vb2: frame_vector.c: don't overwrite error code
DORMANTno replies
From: Hans Verkuil <hidden>
Date: 2021-11-11 10:56:53
Subsystem:
media input infrastructure (v4l/dvb), the rest, videobuf2 framework · Maintainers:
Mauro Carvalho Chehab, Linus Torvalds, Tomasz Figa, Marek Szyprowski
get_vaddr_frames() first calls pin_user_pages_fast() and if that fails tries follow_pfn(). But if that also fails, then the error code from pin_user_pages_fast() is overwritten with the error code from follow_pfn(). Specifically if pin_user_pages_fast() returns -ENOMEM, then follow_pfn() will overwrite that with -EINVAL, which is very confusing. So store the error code from pin_user_pages_fast() and return that if follow_pfn() returns -EINVAL. -EINVAL indicates that the page is unsuitable for follow_pfn, so pin_user_pages_fast() was the correct call to make, and that error code should be returned instead. Signed-off-by: Hans Verkuil <redacted> --- drivers/media/common/videobuf2/frame_vector.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/drivers/media/common/videobuf2/frame_vector.c b/drivers/media/common/videobuf2/frame_vector.c
index ce879f6f8f82..542dde9d2609 100644
--- a/drivers/media/common/videobuf2/frame_vector.c
+++ b/drivers/media/common/videobuf2/frame_vector.c@@ -37,6 +37,7 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames, { struct mm_struct *mm = current->mm; struct vm_area_struct *vma; + int ret_pin_user_pages_fast = 0; int ret = 0; int err;
@@ -56,6 +57,7 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames, vec->is_pfns = false; goto out_unlocked; } + ret_pin_user_pages_fast = ret; mmap_read_lock(mm); vec->got_ref = false;
@@ -71,7 +73,18 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames, while (ret < nr_frames && start + PAGE_SIZE <= vma->vm_end) { err = follow_pfn(vma, start, &nums[ret]); if (err) { - if (ret == 0) + if (ret) + goto out; + // If follow_pfn() returns -EINVAL, then this + // is not an IO mapping or a raw PFN mapping. + // In that case, return the original error from + // pin_user_pages_fast(). Otherwise this + // function would return -EINVAL when + // pin_user_pages_fast() returned -ENOMEM, + // which makes debugging hard. + if (err == -EINVAL && ret_pin_user_pages_fast) + ret = ret_pin_user_pages_fast; + else ret = err; goto out; }
--
2.33.0