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Wed, 01 Jan 2020 09:40:08 -0800 (PST) Date: Wed, 01 Jan 2020 09:40:08 -0800 In-Reply-To: <0000000000006b9e8d059952095e@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <0000000000005e40e3059b17917c@google.com> Subject: Re: KASAN: global-out-of-bounds Read in fbcon_get_font From: syzbot To: b.zolnierkie@samsung.com, daniel.vetter@ffwll.ch, dri-devel@lists.freedesktop.org, ghalat@redhat.com, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, maarten.lankhorst@linux.intel.com, sam@ravnborg.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8"; format=flowed; delsp=yes Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org syzbot has found a reproducer for the following crash on: HEAD commit: 738d2902 Merge git://git.kernel.org/pub/scm/linux/kernel/g.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=14e396c1e00000 kernel config: https://syzkaller.appspot.com/x/.config?x=874bac2ff63646fa dashboard link: https://syzkaller.appspot.com/bug?extid=29d4ed7f3bdedf2aa2fd compiler: gcc (GCC) 9.0.0 20181231 (experimental) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17a0b866e00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15fc963ee00000 Bisection is inconclusive: the bug happens on the oldest tested release. bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=15b75532e00000 final crash: https://syzkaller.appspot.com/x/report.txt?x=17b75532e00000 console output: https://syzkaller.appspot.com/x/log.txt?x=13b75532e00000 IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+29d4ed7f3bdedf2aa2fd@syzkaller.appspotmail.com ================================================================== BUG: KASAN: global-out-of-bounds in memcpy include/linux/string.h:380 [inline] BUG: KASAN: global-out-of-bounds in fbcon_get_font+0x2b2/0x5e0 drivers/video/fbdev/core/fbcon.c:2465 Read of size 32 at addr ffffffff88729e80 by task syz-executor334/10190 CPU: 0 PID: 10190 Comm: syz-executor334 Not tainted 5.5.0-rc4-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x197/0x210 lib/dump_stack.c:118 print_address_description.constprop.0.cold+0x5/0x30b mm/kasan/report.c:374 __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506 kasan_report+0x12/0x20 mm/kasan/common.c:639 check_memory_region_inline mm/kasan/generic.c:185 [inline] check_memory_region+0x134/0x1a0 mm/kasan/generic.c:192 memcpy+0x24/0x50 mm/kasan/common.c:125 memcpy include/linux/string.h:380 [inline] fbcon_get_font+0x2b2/0x5e0 drivers/video/fbdev/core/fbcon.c:2465 con_font_get drivers/tty/vt/vt.c:4446 [inline] con_font_op+0x20b/0x1270 drivers/tty/vt/vt.c:4605 vt_ioctl+0xd2e/0x26d0 drivers/tty/vt/vt_ioctl.c:913 tty_ioctl+0xa37/0x14f0 drivers/tty/tty_io.c:2660 vfs_ioctl fs/ioctl.c:47 [inline] file_ioctl fs/ioctl.c:545 [inline] do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732 ksys_ioctl+0xab/0xd0 fs/ioctl.c:749 __do_sys_ioctl fs/ioctl.c:756 [inline] __se_sys_ioctl fs/ioctl.c:754 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4412d9 Code: e8 3c ad 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 9b 09 fc ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007ffc49b97f18 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00000000004a2487 RCX: 00000000004412d9 RDX: 0000000020000200 RSI: 0000000000004b60 RDI: 0000000000000004 RBP: 0000000000018ac7 R08: 000000000000000d R09: 00000000004002c8 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402100 R13: 0000000000402190 R14: 0000000000000000 R15: 0000000000000000 The buggy address belongs to the variable: fontdata_8x16+0x1000/0x1120 Memory state around the buggy address: ffffffff88729d80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffffffff88729e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > ffffffff88729e80: fa fa fa fa 06 fa fa fa fa fa fa fa 05 fa fa fa ^ ffffffff88729f00: fa fa fa fa 06 fa fa fa fa fa fa fa 00 00 03 fa ffffffff88729f80: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00 00 ==================================================================