Re: [syzbot] Discardable change

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@xxxxxxxxxxxxxxx, syzkaller-bugs@xxxxxxxxxxxxxxxx.

***

Subject: Discardable change
Author: yuran.pereira@xxxxxxxxxxx

#syz test: https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux.git master

---
 drivers/usb/core/devio.c | 2 ++
 include/linux/page_ext.h | 1 +
 2 files changed, 3 insertions(+)

diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 3beb6a862e80..22ae7babf46b 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -276,12 +276,14 @@ static int usbdev_mmap(struct file *file, struct vm_area_struct *vma)
 		if (remap_pfn_range(vma, vma->vm_start,
 				    virt_to_phys(usbm->mem) >> PAGE_SHIFT,
 				    size, vma->vm_page_prot) < 0) {
+			pr_info("==> if* vma_use_count %d\n", usbm->vma_use_count);
 			dec_usb_memory_use_count(usbm, &usbm->vma_use_count);
 			return -EAGAIN;
 		}
 	} else {
 		if (dma_mmap_coherent(hcd->self.sysdev, vma, mem, dma_handle,
 				      size)) {
+			pr_info("==> else* vma_use_count %d\n", usbm->vma_use_count);
 			dec_usb_memory_use_count(usbm, &usbm->vma_use_count);
 			return -EAGAIN;
 		}
diff --git a/include/linux/page_ext.h b/include/linux/page_ext.h
index be98564191e6..fb3e7dcfbffb 100644
--- a/include/linux/page_ext.h
+++ b/include/linux/page_ext.h
@@ -84,6 +84,7 @@ extern void page_ext_put(struct page_ext *page_ext);
 static inline void *page_ext_data(struct page_ext *page_ext,
 				  struct page_ext_operations *ops)
 {
+	pr_info("==> offset = %ld\n", ops->offset);
 	return (void *)(page_ext) + ops->offset;
 }
 
-- 
2.25.1