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>
CC: <stable@vger.kernel.org>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
faab50984f