usb/gadget: null-ptr-deref in dev_ioctl

[Andrey Konovalov]

Hi!

It seems that gadget->ops can be NULL so it probably needs to be
checked as well as gadget->ops->ioctl in dev_ioctl() in
drivers/usb/gadget/legacy/inode.c.

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Modules linked in:
CPU: 1 PID: 5214 Comm: syz-executor Not tainted 4.13.0+ #94
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
task: ffff88006ac0e800 task.stack: ffff88006af60000
! handling hub events now: start
RIP: 0010:dev_ioctl+0x117/0x280 drivers/usb/gadget/legacy/inode.c:1323
RSP: 0018:ffff88006af67c30 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 1ffff1000d5ecf86 RCX: ffffc90000ab5000
RDX: 0000000000000005 RSI: ffffffff83f1c482 RDI: 0000000000000028
RBP: ffff88006af67cf8 R08: ffffed000d5ecf80 R09: ffffed000d5ecf81
R10: ffff88006af67ed8 R11: 0000000000000000 R12: 0000000000000414
R13: 0000000000000000 R14: dffffc0000000000 R15: 0000000000000000
FS:  00007fd2fcbc1700(0000) GS:ffff88006c900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000006e30a0 CR3: 000000006a3ef000 CR4: 00000000000006e0
Call Trace:
 vfs_ioctl fs/ioctl.c:45
 do_vfs_ioctl+0x1d2/0x1560 fs/ioctl.c:685
 SYSC_ioctl fs/ioctl.c:700
 SyS_ioctl+0x94/0xc0 fs/ioctl.c:691
 entry_SYSCALL_64_fastpath+0x1a/0xa5 arch/x86/entry/entry_64.S:203
RIP: 0033:0x447727
RSP: 002b:00007fd2fcbc0bd8 EFLAGS: 00000206 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000708000 RCX: 0000000000447727
RDX: 0000000000000000 RSI: 0000000000000414 RDI: 0000000000000005
RBP: 0000000000005da0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000005
R13: 00000000ffffffff R14: 000000000000004c R15: 0000000020003000
Code: 80 96 50 fd 41 81 fc 42 42 00 00 0f 84 b3 00 00 00 e8 6e 96 50
fd 49 8d 7f 28 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80>
3c 02 00 0f 85 4e 01 00 00 4d 8b 77 28 48 b8 00 00 00 00 00
RIP: dev_ioctl+0x117/0x280 RSP: ffff88006af67c30
---[ end trace 2fb9696e75c067ba ]---