On Sat, Apr 09, 2022 at 08:09:00PM +0800, Dongliang Mu wrote: > From: Dongliang Mu <mudongliangabcd@xxxxxxxxx> > > cdc_ncm_bind calls cdc_ncm_bind_common and sets dev->data[0] > with ctx. However, in the unbind function - cdc_ncm_unbind, > it calls cdc_ncm_free and frees ctx, leaving dev->data[0] as > a dangling pointer. The following ioctl operation will trigger > the UAF in the function cdc_ncm_set_dgram_size. > > Fix this by setting dev->data[0] as zero. This sounds like a poor band-aid. Please explain how this prevent the ioctl() from racing with unbind(). Johan > ================================================================== > BUG: KASAN: use-after-free in cdc_ncm_set_dgram_size+0xc91/0xde0 > Read of size 8 at addr ffff8880755210b0 by task dhcpcd/3174 > > Call Trace: > <TASK> > __dump_stack lib/dump_stack.c:88 [inline] > dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 > print_address_description.constprop.0.cold+0xeb/0x495 mm/kasan/report.c:313 > print_report mm/kasan/report.c:429 [inline] > kasan_report.cold+0xf4/0x1c6 mm/kasan/report.c:491 > cdc_ncm_set_dgram_size+0xc91/0xde0 drivers/net/usb/cdc_ncm.c:608 > cdc_ncm_change_mtu+0x10c/0x140 drivers/net/usb/cdc_ncm.c:798 > __dev_set_mtu net/core/dev.c:8519 [inline] > dev_set_mtu_ext+0x352/0x5b0 net/core/dev.c:8572 > dev_set_mtu+0x8e/0x120 net/core/dev.c:8596 > dev_ifsioc+0xb87/0x1090 net/core/dev_ioctl.c:332 > dev_ioctl+0x1b9/0xe30 net/core/dev_ioctl.c:586 > sock_do_ioctl+0x15a/0x230 net/socket.c:1136 > sock_ioctl+0x2f1/0x640 net/socket.c:1239 > vfs_ioctl fs/ioctl.c:51 [inline] > __do_sys_ioctl fs/ioctl.c:870 [inline] > __se_sys_ioctl fs/ioctl.c:856 [inline] > __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x35/0x80 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x44/0xae > RIP: 0033:0x7f00859e70e7 > RSP: 002b:00007ffedd503dd8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 > RAX: ffffffffffffffda RBX: 00007f00858f96c8 RCX: 00007f00859e70e7 > RDX: 00007ffedd513fc8 RSI: 0000000000008922 RDI: 0000000000000018 > RBP: 00007ffedd524178 R08: 00007ffedd513f88 R09: 00007ffedd513f38 > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 > R13: 00007ffedd513fc8 R14: 0000000000000028 R15: 0000000000008922 > </TASK> > Reported-by: syzbot+eabbf2aaa999cc507108@xxxxxxxxxxxxxxxxxxxxxxxxx > Signed-off-by: Dongliang Mu <mudongliangabcd@xxxxxxxxx> > --- > drivers/net/usb/cdc_ncm.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c > index 15f91d691bba..9fc2df9f0b63 100644 > --- a/drivers/net/usb/cdc_ncm.c > +++ b/drivers/net/usb/cdc_ncm.c > @@ -1019,6 +1019,7 @@ void cdc_ncm_unbind(struct usbnet *dev, struct usb_interface *intf) > > usb_set_intfdata(intf, NULL); > cdc_ncm_free(ctx); > + dev->data[0] = 0; > } > EXPORT_SYMBOL_GPL(cdc_ncm_unbind);
