usb: usbfs: Enforce page requirements for mmap

The current implementation of usbdev_mmap uses usb_alloc_coherent to
allocate memory pages that will later be mapped into the user space.
Meanwhile, usb_alloc_coherent employs three different methods to
allocate memory, as outlined below:
 * If hcd->localmem_pool is non-null, it uses gen_pool_dma_alloc to
   allocate memory;
 * If DMA is not available, it uses kmalloc to allocate memory;
 * Otherwise, it uses dma_alloc_coherent.

However, it should be noted that gen_pool_dma_alloc does not guarantee
that the resulting memory will be page-aligned. Furthermore, trying to
map slab pages (i.e., memory allocated by kmalloc) into the user space
is not resonable and can lead to problems, such as a type confusion bug
when PAGE_TABLE_CHECK=y [1].

To address these issues, this patch introduces hcd_alloc_coherent_pages,
which addresses the above two problems. Specifically,
hcd_alloc_coherent_pages uses gen_pool_dma_alloc_align instead of
gen_pool_dma_alloc to ensure that the memory is page-aligned. To replace
kmalloc, hcd_alloc_coherent_pages directly allocates pages by calling
__get_free_pages.

Reported-by: syzbot+fcf1a817ceb50935ce99@syzkaller.appspotmail.comm
Closes: https://lore.kernel.org/lkml/000000000000258e5e05fae79fc1@google.com/ [1]
Fixes: f7d34b445abc ("USB: Add support for usbfs zerocopy.")
Fixes: ff2437befd8f ("usb: host: Fix excessive alignment restriction for local memory allocations")
Cc: stable@vger.kernel.org
Signed-off-by: Ruihan Li <lrh2000@pku.edu.cn>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/20230515130958.32471-2-lrh2000@pku.edu.cn
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/include/linux/usb/hcd.h b/include/linux/usb/hcd.h
index 094c77eaf455..0c7eff91adf4 100644
--- a/include/linux/usb/hcd.h
+++ b/include/linux/usb/hcd.h
@@ -501,6 +501,11 @@ void *hcd_buffer_alloc(struct usb_bus *bus, size_t size,
 void hcd_buffer_free(struct usb_bus *bus, size_t size,
 	void *addr, dma_addr_t dma);
 
+void *hcd_buffer_alloc_pages(struct usb_hcd *hcd,
+		size_t size, gfp_t mem_flags, dma_addr_t *dma);
+void hcd_buffer_free_pages(struct usb_hcd *hcd,
+		size_t size, void *addr, dma_addr_t dma);
+
 /* generic bus glue, needed for host controllers that don't use PCI */
 extern irqreturn_t usb_hcd_irq(int irq, void *__hcd);