| From: Alan Stern <stern@rowland.harvard.edu> |
| Date: Fri, 9 Dec 2016 15:17:46 -0500 |
| Subject: USB: gadgetfs: fix unbounded memory allocation bug |
| |
| commit faab50984fe6636e616c7cc3d30308ba391d36fd upstream. |
| |
| Andrey Konovalov reports that fuzz testing with syzkaller causes a |
| KASAN warning in gadgetfs: |
| |
| BUG: KASAN: slab-out-of-bounds in dev_config+0x86f/0x1190 at addr ffff88003c47e160 |
| Write of size 65537 by task syz-executor0/6356 |
| CPU: 3 PID: 6356 Comm: syz-executor0 Not tainted 4.9.0-rc7+ #19 |
| Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 |
| ffff88003c107ad8 ffffffff81f96aba ffffffff3dc11ef0 1ffff10007820eee |
| ffffed0007820ee6 ffff88003dc11f00 0000000041b58ab3 ffffffff8598b4c8 |
| ffffffff81f96828 ffffffff813fb4a0 ffff88003b6eadc0 ffff88003c107738 |
| Call Trace: |
| [< inline >] __dump_stack lib/dump_stack.c:15 |
| [<ffffffff81f96aba>] dump_stack+0x292/0x398 lib/dump_stack.c:51 |
| [<ffffffff817e4dec>] kasan_object_err+0x1c/0x70 mm/kasan/report.c:159 |
| [< inline >] print_address_description mm/kasan/report.c:197 |
| [<ffffffff817e5080>] kasan_report_error+0x1f0/0x4e0 mm/kasan/report.c:286 |
| [<ffffffff817e5705>] kasan_report+0x35/0x40 mm/kasan/report.c:306 |
| [< inline >] check_memory_region_inline mm/kasan/kasan.c:308 |
| [<ffffffff817e3fb9>] check_memory_region+0x139/0x190 mm/kasan/kasan.c:315 |
| [<ffffffff817e4044>] kasan_check_write+0x14/0x20 mm/kasan/kasan.c:326 |
| [< inline >] copy_from_user arch/x86/include/asm/uaccess.h:689 |
| [< inline >] ep0_write drivers/usb/gadget/legacy/inode.c:1135 |
| [<ffffffff83228caf>] dev_config+0x86f/0x1190 drivers/usb/gadget/legacy/inode.c:1759 |
| [<ffffffff817fdd55>] __vfs_write+0x5d5/0x760 fs/read_write.c:510 |
| [<ffffffff817ff650>] vfs_write+0x170/0x4e0 fs/read_write.c:560 |
| [< inline >] SYSC_write fs/read_write.c:607 |
| [<ffffffff81803a5b>] SyS_write+0xfb/0x230 fs/read_write.c:599 |
| [<ffffffff84f47ec1>] entry_SYSCALL_64_fastpath+0x1f/0xc2 |
| |
| Indeed, there is a comment saying that the value of len is restricted |
| to a 16-bit integer, but the code doesn't actually do this. |
| |
| This patch fixes the warning. It replaces the comment with a |
| computation that forces the amount of data copied from the user in |
| ep0_write() to be no larger than the wLength size for the control |
| transfer, which is a 16-bit quantity. |
| |
| Signed-off-by: Alan Stern <stern@rowland.harvard.edu> |
| Reported-by: Andrey Konovalov <andreyknvl@google.com> |
| Tested-by: Andrey Konovalov <andreyknvl@google.com> |
| Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com> |
| [bwh: Backported to 3.16: adjust filename] |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| --- |
| drivers/usb/gadget/inode.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/drivers/usb/gadget/inode.c |
| +++ b/drivers/usb/gadget/inode.c |
| @@ -1200,7 +1200,7 @@ ep0_write (struct file *fd, const char _ |
| /* data and/or status stage for control request */ |
| } else if (dev->state == STATE_DEV_SETUP) { |
| |
| - /* IN DATA+STATUS caller makes len <= wLength */ |
| + len = min_t(size_t, len, dev->setup_wLength); |
| if (dev->setup_in) { |
| retval = setup_req (dev->gadget->ep0, dev->req, len); |
| if (retval == 0) { |