From 89ab2d39643e5ce2b122baa1e76176d1bd984cec Mon Sep 17 00:00:00 2001 From: Hans Verkuil Date: Thu, 11 Nov 2021 11:56:29 +0100 Subject: [PATCH] media: vb2: frame_vector.c: don't overwrite error code 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 Signed-off-by: Mauro Carvalho Chehab --- 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 ce879f6f8f829..542dde9d2609b 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; } -- 2.30.2