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Tue, 30 Oct 2018 20:17:03 -0700 (PDT) Date: Tue, 30 Oct 2018 20:17:03 -0700 In-Reply-To: <00000000000095ce6305795aafbb@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <000000000000793b4005797dbc40@google.com> Subject: Re: KASAN: null-ptr-deref Write in kthread_stop From: syzbot To: hverkuil@xs4all.nl, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, mchehab@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: 6201f31a39f8 Add linux-next specific files for 20181030 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=179da7cb400000 kernel config: https://syzkaller.appspot.com/x/.config?x=2a22859d870756c1 dashboard link: https://syzkaller.appspot.com/bug?extid=53d5b2df0d9744411e2e compiler: gcc (GCC) 8.0.1 20180413 (experimental) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=106f6999400000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17267233400000 IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+53d5b2df0d9744411e2e@syzkaller.appspotmail.com sshd (5629) used greatest stack depth: 15744 bytes left ================================================================== BUG: KASAN: null-ptr-deref in atomic_inc include/asm-generic/atomic-instrumented.h:109 [inline] BUG: KASAN: null-ptr-deref in kthread_stop+0x108/0x8f0 kernel/kthread.c:545 Write of size 4 at addr 0000000000000020 by task syz-executor789/5655 CPU: 1 PID: 5655 Comm: syz-executor789 Not tainted 4.19.0-next-20181030+ #101 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+0x244/0x39d lib/dump_stack.c:113 kasan_report_error mm/kasan/report.c:352 [inline] kasan_report.cold.8+0x6d/0x309 mm/kasan/report.c:412 check_memory_region_inline mm/kasan/kasan.c:260 [inline] check_memory_region+0x13e/0x1b0 mm/kasan/kasan.c:267 kasan_check_write+0x14/0x20 mm/kasan/kasan.c:278 atomic_inc include/asm-generic/atomic-instrumented.h:109 [inline] kthread_stop+0x108/0x8f0 kernel/kthread.c:545 vivid_stop_generating_vid_cap+0x2bc/0x93b drivers/media/platform/vivid/vivid-kthread-cap.c:919 vid_cap_stop_streaming+0x8d/0xe0 drivers/media/platform/vivid/vivid-vid-cap.c:259 __vb2_queue_cancel+0x171/0xca0 drivers/media/common/videobuf2/videobuf2-core.c:1668 vb2_core_streamoff+0x60/0x140 drivers/media/common/videobuf2/videobuf2-core.c:1804 __vb2_cleanup_fileio+0x73/0x160 drivers/media/common/videobuf2/videobuf2-core.c:2325 vb2_core_queue_release+0x1e/0x80 drivers/media/common/videobuf2/videobuf2-core.c:2052 vb2_queue_release drivers/media/common/videobuf2/videobuf2-v4l2.c:672 [inline] _vb2_fop_release+0x1d2/0x2b0 drivers/media/common/videobuf2/videobuf2-v4l2.c:843 vb2_fop_release+0x77/0xc0 drivers/media/common/videobuf2/videobuf2-v4l2.c:857 vivid_fop_release+0x18e/0x440 drivers/media/platform/vivid/vivid-core.c:474 v4l2_release+0xfb/0x1a0 drivers/media/v4l2-core/v4l2-dev.c:448 __fput+0x3bc/0xa70 fs/file_table.c:279 ____fput+0x15/0x20 fs/file_table.c:312 task_work_run+0x1e8/0x2a0 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline] syscall_return_slowpath arch/x86/entry/common.c:268 [inline] do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x400ef0 Code: 01 f0 ff ff 0f 83 b0 0a 00 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 83 3d dd 57 2d 00 00 75 14 b8 03 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 84 0a 00 00 c3 48 83 ec 08 e8 3a 01 00 00 RSP: 002b:00007fff00659738 EFLAGS: 00000246 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000400ef0 RDX: 0000000020000024 RSI: 0000000020000000 RDI: 0000000000000003 RBP: 0000000000000000 R08: 0000000001446880 R09: 00000000004002e0 R10: 000000000000000f R11: 0000000000000246 R12: 0000000000401e00 R13: 0000000000401e90 R14: 0000000000000000 R15: 0000000000000000 ==================================================================