diff options
| author | Alan Stern <stern@rowland.harvard.edu> | 2016-12-09 15:18:43 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-01-12 11:22:44 +0100 |
| commit | 74e36bffe645ba71e60f89d36256100c9cbdeb04 (patch) | |
| tree | 85fe02fe2dc2b34b2206c772f2ffdb09819f96f5 | |
| parent | fe75330a27fcd9fe180242857f27e8c1b9bf920d (diff) | |
USB: gadgetfs: fix use-after-free bug
commit add333a81a16abbd4f106266a2553677a165725f upstream.
Andrey Konovalov reports that fuzz testing with syzkaller causes a
KASAN use-after-free bug report in gadgetfs:
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
The cause of the bug is subtle. The dev_config() routine gets called
twice by the fuzzer. The first time, the user data contains both a
full-speed configuration descriptor and a high-speed config
descriptor, causing dev->hs_config to be set. But it also contains an
invalid device descriptor, so the buffer containing the descriptors is
deallocated and dev_config() returns an error.
The second time dev_config() is called, the user data contains only a
full-speed config descriptor. But dev->hs_config still has the stale
pointer remaining from the first call, causing the routine to think
that there is a valid high-speed config. Later on, when the driver
dereferences the stale pointer to copy that descriptor, we get a
use-after-free access.
The fix is simple: Clear dev->hs_config if the passed-in data does not
contain a high-speed config descriptor.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/usb/gadget/legacy/inode.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c index ee0eec47838e..509b5fbbeeec 100644 --- a/drivers/usb/gadget/legacy/inode.c +++ b/drivers/usb/gadget/legacy/inode.c @@ -1821,6 +1821,8 @@ dev_config (struct file *fd, const char __user *buf, size_t len, loff_t *ptr) goto fail; kbuf += total; length -= total; + } else { + dev->hs_config = NULL; } /* could support multiple configs, using another encoding! */ |