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Date: Sun, 29 May 2016 21:04:17 +0200 From: Pavel Machek <pavel@....cz> To: Sasha Levin <sasha.levin@...cle.com>, vojtech@...e.cz Cc: gregkh@...uxfoundation.org, jslaby@...e.com, dmitry.torokhov@...il.com, LKML <linux-kernel@...r.kernel.org> Subject: Re: tty/vt/keyboard: out of bounds access in do_compute_shiftstate Hi! (Vojtech added to cc list. This is history.) > I've hit the following while fuzzing with syzkaller inside a KVM tools guest > running the latest -next kernel: What does syzkaller do? Random syscalls? > [ 2662.777566] BUG: KASAN: global-out-of-bounds in do_compute_shiftstate+0x161/0x370 at addr ffffffffb2e686a0 > > [ 2662.777592] Read of size 2 by task syz-executor/30576 > > [ 2662.777676] Address belongs to variable plain_map+0x200/0x3540 > /* * Called after returning from RAW mode or when changing consoles - recompute * shift_down[] and shift_state from key_down[] maybe called when keymap is * undefined, so that shiftkey release is seen. The caller must hold the * kbd_event_lock. */ static void do_compute_shiftstate(void) { unsigned int i, j, k, sym, val; shift_state = 0; memset(shift_down, 0, sizeof(shift_down)); for (i = 0; i < ARRAY_SIZE(key_down); i++) { if (!key_down[i]) continue; k = i * BITS_PER_LONG; for (j = 0; j < BITS_PER_LONG; j++, k++) { if (!test_bit(k, key_down)) continue; sym = U(key_maps[0][k]); if (KTYP(sym) != KT_SHIFT && KTYP(sym) != KT_SLOCK) continue; val = KVAL(sym); if (val == KVAL(K_CAPSSHIFT)) val = KVAL(K_SHIFT); shift_down[val]++; shift_state |= (1 << val); } } } Best regards, Pavel > [ 2662.777727] CPU: 2 PID: 30576 Comm: syz-executor Tainted: G B 4.6.0-next-20160527-sasha-00024-g6ab0dc9-dirty #3098 > > [ 2662.777792] 1ffff1001635bde7 00000000dc4d92d7 ffff8800b1adefc0 ffffffffa3fd0b37 > > [ 2662.777826] ffffffff00000002 fffffbfff5deeda4 0000000041b58ab3 ffffffffae8dd830 > > [ 2662.777862] ffffffffa3fd09c8 ffffffffa23fa2e8 ffff8800b1adef98 ffff8801d42a20f8 > > [ 2662.777868] Call Trace: > > [ 2662.777935] dump_stack (lib/dump_stack.c:53) > [ 2662.778136] kasan_report_error (include/linux/kasan.h:28 mm/kasan/report.c:211 mm/kasan/report.c:277) > [ 2662.778265] __asan_report_load2_noabort (mm/kasan/report.c:317) > [ 2662.778318] do_compute_shiftstate (drivers/tty/vt/keyboard.c:386) > [ 2662.778332] fn_null (drivers/tty/vt/keyboard.c:625) > [ 2662.778345] k_spec (drivers/tty/vt/keyboard.c:645) > [ 2662.778361] kbd_event (drivers/tty/vt/keyboard.c:1459 drivers/tty/vt/keyboard.c:1475) > [ 2662.778907] input_to_handler (drivers/input/input.c:120 (discriminator 3)) > [ 2662.778926] input_pass_values (drivers/input/input.c:148) > [ 2662.778944] input_handle_event (drivers/input/input.c:406) > [ 2662.779015] input_inject_event (include/linux/rcupdate.h:910 drivers/input/input.c:467) > [ 2662.779034] evdev_do_ioctl (drivers/input/evdev.c:1102) > [ 2662.779271] evdev_ioctl_handler (drivers/input/evdev.c:1302) > [ 2662.779305] evdev_ioctl (drivers/input/evdev.c:1312) > [ 2662.779320] do_vfs_ioctl (fs/ioctl.c:44 fs/ioctl.c:674) > [ 2662.779463] SyS_ioctl (fs/ioctl.c:689 fs/ioctl.c:680) > [ 2662.779511] do_syscall_64 (arch/x86/entry/common.c:350) > [ 2662.779530] entry_SYSCALL64_slow_path (arch/x86/entry/entry_64.S:251) > [ 2662.779535] Memory state around the buggy address: > > [ 2662.779566] ffffffffb2e68580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > > [ 2662.779579] ffffffffb2e68600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > > [ 2662.779589] >ffffffffb2e68680: 00 00 00 00 fa fa fa fa 00 00 00 00 00 00 00 00 > > [ 2662.779594] ^ > > [ 2662.779604] ffffffffb2e68700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > > [ 2662.779615] ffffffffb2e68780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > > > Thanks, > Sasha -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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