usb/gadget: use-after-free in gadgetfs_setup

[Andrey Konovalov]

Hi!

I've got the following error report while running the syzkaller fuzzer.

On commit 3c49de52d5647cda8b42c4255cf8a29d1e22eff5 (Dec 2).

BUG: KASAN: use-after-free in gadgetfs_setup+0x208a/0x20e0 at addr
ffff88003dfe5bf2
Read of size 2 by task syz-executor0/22994
CPU: 3 PID: 22994 Comm: syz-executor0 Not tainted 4.9.0-rc7+ #16
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
 ffff88006df06a18 ffffffff81f96aba ffffffffe0528500 1ffff1000dbe0cd6
 ffffed000dbe0cce ffff88006df068f0 0000000041b58ab3 ffffffff8598b4c8
 ffffffff81f96828 1ffff1000dbe0ccd ffff88006df06708 ffff88006df06748
Call Trace:
 <IRQ> [  201.343209]  [<     inline     >] __dump_stack lib/dump_stack.c:15
 <IRQ> [  201.343209]  [<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
 [<     inline     >] kasan_report mm/kasan/report.c:306
 [<ffffffff817e562a>] __asan_report_load_n_noabort+0x3a/0x40
mm/kasan/report.c:337
 [<     inline     >] config_buf drivers/usb/gadget/legacy/inode.c:1298
 [<ffffffff8322c8fa>] gadgetfs_setup+0x208a/0x20e0
drivers/usb/gadget/legacy/inode.c:1368
 [<ffffffff830fdcd0>] dummy_timer+0x11f0/0x36d0
drivers/usb/gadget/udc/dummy_hcd.c:1858
 [<ffffffff814807c1>] call_timer_fn+0x241/0x800 kernel/time/timer.c:1308
 [<     inline     >] expire_timers kernel/time/timer.c:1348
 [<ffffffff81482de6>] __run_timers+0xa06/0xec0 kernel/time/timer.c:1641
 [<ffffffff814832c1>] run_timer_softirq+0x21/0x80 kernel/time/timer.c:1654
 [<ffffffff84f4af8b>] __do_softirq+0x2fb/0xb63 kernel/softirq.c:284
 [<     inline     >] invoke_softirq kernel/softirq.c:364
 [<ffffffff812d3b8e>] irq_exit+0x19e/0x1d0 kernel/softirq.c:405
 [<     inline     >] exiting_irq arch/x86/include/asm/apic.h:659
 [<ffffffff84f4a59b>] smp_apic_timer_interrupt+0x7b/0xa0
arch/x86/kernel/apic/apic.c:960
 [<ffffffff84f4964c>] apic_timer_interrupt+0x8c/0xa0
arch/x86/entry/entry_64.S:489
 <EOI> [  201.343209]  [<ffffffff84f472f9>] ?
_raw_spin_unlock_irqrestore+0x119/0x1a0
 [<ffffffff8136f9e4>] try_to_wake_up+0x174/0x1160 kernel/sched/core.c:2099
 [<     inline     >] wake_up_process kernel/sched/core.c:2165
 [<ffffffff81370a7a>] wake_up_q+0x8a/0xe0 kernel/sched/core.c:469
 [<ffffffff814cc6de>] futex_wake+0x5be/0x6c0 kernel/futex.c:1453
 [<ffffffff814d41dd>] do_futex+0x11bd/0x1f00 kernel/futex.c:3219
 [<     inline     >] SYSC_futex kernel/futex.c:3275
 [<ffffffff814d521c>] SyS_futex+0x2fc/0x400 kernel/futex.c:3243
 [<ffffffff84f47ec1>] entry_SYSCALL_64_fastpath+0x1f/0xc2
Object at ffff88003dfe5bf0, in cache kmalloc-32 size: 32
Allocated:
PID = 21625
 [  201.343209] [<ffffffff81203526>] save_stack_trace+0x16/0x20
arch/x86/kernel/stacktrace.c:57
 [  201.343209] [<ffffffff817e40d3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:495
 [  201.343209] [<     inline     >] set_track mm/kasan/kasan.c:507
 [  201.343209] [<ffffffff817e435d>] kasan_kmalloc+0xad/0xe0
mm/kasan/kasan.c:598
 [  201.343209] [<ffffffff817e4932>] kasan_slab_alloc+0x12/0x20
mm/kasan/kasan.c:537
 [  201.343209] [<     inline     >] slab_post_alloc_hook mm/slab.h:417
 [  201.343209] [<     inline     >] slab_alloc_node mm/slub.c:2708
 [  201.343209] [<     inline     >] slab_alloc mm/slub.c:2716
 [  201.343209] [<ffffffff817e3465>]
__kmalloc_track_caller+0x195/0x290 mm/slub.c:4240
 [  201.343209] [<ffffffff8171bb1c>] memdup_user+0x2c/0xa0 mm/util.c:137
 [  201.343209] [<ffffffff8322872b>] dev_config+0x2eb/0x1190
drivers/usb/gadget/legacy/inode.c:1778
 [  201.343209] [<ffffffff817fdd55>] __vfs_write+0x5d5/0x760 fs/read_write.c:510
 [  201.343209] [<ffffffff817ff650>] vfs_write+0x170/0x4e0 fs/read_write.c:560
 [  201.343209] [<     inline     >] SYSC_write fs/read_write.c:607
 [  201.343209] [<ffffffff81803a5b>] SyS_write+0xfb/0x230 fs/read_write.c:599
 [  201.343209] [<ffffffff84f47ec1>] entry_SYSCALL_64_fastpath+0x1f/0xc2
Freed:
PID = 21625
 [  201.343209] [<ffffffff81203526>] save_stack_trace+0x16/0x20
arch/x86/kernel/stacktrace.c:57
 [  201.343209] [<ffffffff817e40d3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:495
 [  201.343209] [<     inline     >] set_track mm/kasan/kasan.c:507
 [  201.343209] [<ffffffff817e49b3>] kasan_slab_free+0x73/0xc0
mm/kasan/kasan.c:571
 [  201.343209] [<     inline     >] slab_free_hook mm/slub.c:1352
 [  201.343209] [<     inline     >] slab_free_freelist_hook mm/slub.c:1374
 [  201.343209] [<     inline     >] slab_free mm/slub.c:2951
 [  201.343209] [<ffffffff817e0e17>] kfree+0xe7/0x2b0 mm/slub.c:3871
 [  201.343209] [<ffffffff8322904b>] dev_config+0xc0b/0x1190
drivers/usb/gadget/legacy/inode.c:1848
 [  201.343209] [<ffffffff817fdd55>] __vfs_write+0x5d5/0x760 fs/read_write.c:510
 [  201.343209] [<ffffffff817ff650>] vfs_write+0x170/0x4e0 fs/read_write.c:560
 [  201.343209] [<     inline     >] SYSC_write fs/read_write.c:607
 [  201.343209] [<ffffffff81803a5b>] SyS_write+0xfb/0x230 fs/read_write.c:599
 [  201.343209] [<ffffffff84f47ec1>] entry_SYSCALL_64_fastpath+0x1f/0xc2
Memory state around the buggy address:
 ffff88003dfe5a80: fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88003dfe5b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88003dfe5b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fb fb
                                                             ^
 ffff88003dfe5c00: fb fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88003dfe5c80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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