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Wed, 18 Dec 2019 11:21:09 -0800 (PST) Date: Wed, 18 Dec 2019 11:21:09 -0800 In-Reply-To: <0000000000007b17010598f7aa1f@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <000000000000d794080599ff586a@google.com> Subject: Re: KASAN: global-out-of-bounds Read in bit_putcs From: syzbot To: b.zolnierkie@samsung.com, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.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: b9c5ef25 Add linux-next specific files for 20191218 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=17d57b46e00000 kernel config: https://syzkaller.appspot.com/x/.config?x=2eb13492323f151f dashboard link: https://syzkaller.appspot.com/bug?extid=38a3699c7eaf165b97a6 compiler: gcc (GCC) 9.0.0 20181231 (experimental) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13ce1f2ee00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=125727dee00000 Bisection is inconclusive: the bug happens on the oldest tested release. bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=12caa5b6e00000 final crash: https://syzkaller.appspot.com/x/report.txt?x=11caa5b6e00000 console output: https://syzkaller.appspot.com/x/log.txt?x=16caa5b6e00000 IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+38a3699c7eaf165b97a6@syzkaller.appspotmail.com ================================================================== BUG: KASAN: global-out-of-bounds in __fb_pad_aligned_buffer include/linux/fb.h:654 [inline] BUG: KASAN: global-out-of-bounds in bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline] BUG: KASAN: global-out-of-bounds in bit_putcs+0xd5d/0xf10 drivers/video/fbdev/core/bitblit.c:185 Read of size 1 at addr ffffffff8872bb44 by task syz-executor093/14101 CPU: 1 PID: 14101 Comm: syz-executor093 Not tainted 5.5.0-rc2-next-20191218-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 __asan_report_load1_noabort+0x14/0x20 mm/kasan/generic_report.c:132 __fb_pad_aligned_buffer include/linux/fb.h:654 [inline] bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline] bit_putcs+0xd5d/0xf10 drivers/video/fbdev/core/bitblit.c:185 fbcon_putcs+0x33c/0x3e0 drivers/video/fbdev/core/fbcon.c:1353 do_update_region+0x42b/0x6f0 drivers/tty/vt/vt.c:677 redraw_screen+0x676/0x7d0 drivers/tty/vt/vt.c:1011 fbcon_do_set_font+0x829/0x960 drivers/video/fbdev/core/fbcon.c:2605 fbcon_copy_font+0x12c/0x190 drivers/video/fbdev/core/fbcon.c:2620 con_font_copy drivers/tty/vt/vt.c:4594 [inline] con_font_op+0x6b2/0x1270 drivers/tty/vt/vt.c:4609 vt_ioctl+0x181a/0x26d0 drivers/tty/vt/vt_ioctl.c:965 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: 0033:0x449c49 Code: e8 7c e6 ff ff 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 1b 05 fc ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fa99f42ace8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00000000006e6a38 RCX: 0000000000449c49 RDX: 0000000020000000 RSI: 0000000000004b72 RDI: 0000000000000004 RBP: 00000000006e6a30 R08: 00007fa99f42b700 R09: 0000000000000000 R10: 00007fa99f42b700 R11: 0000000000000246 R12: 00000000006e6a3c R13: 00007ffe46ffe5df R14: 00007fa99f42b9c0 R15: 20c49ba5e353f7cf The buggy address belongs to the variable: __func__.44397+0x104/0x1c0 Memory state around the buggy address: ffffffff8872ba00: 00 00 00 00 fa fa fa fa 00 03 fa fa fa fa fa fa ffffffff8872ba80: 00 01 fa fa fa fa fa fa 04 fa fa fa fa fa fa fa > ffffffff8872bb00: 04 fa fa fa fa fa fa fa 04 fa fa fa fa fa fa fa ^ ffffffff8872bb80: 04 fa fa fa fa fa fa fa 07 fa fa fa fa fa fa fa ffffffff8872bc00: 04 fa fa fa fa fa fa fa 00 00 01 fa fa fa fa fa ==================================================================