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Fri, 21 Apr 2023 08:15:14 -0700 (PDT) MIME-Version: 1.0 References: <000000000000b9915d05f9d98bdd@google.com> In-Reply-To: From: Alexei Starovoitov Date: Fri, 21 Apr 2023 08:15:03 -0700 Message-ID: Subject: Re: [syzbot] [ext4?] [mm?] KCSAN: data-race in strscpy / strscpy (3) To: Dmitry Vyukov Cc: syzbot , adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, Linux-Fsdevel , LKML , linux-mm , clang-built-linux , Nathan Chancellor , Nick Desaulniers , syzkaller-bugs , Tom Rix , "Theodore Ts'o" , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , bpf , KP Singh Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: 3C39118001D X-Rspamd-Server: rspam09 X-Stat-Signature: 9brg4hrochd8ed5m9n5t6zsm57ppwkx5 X-HE-Tag: 1682090115-547275 X-HE-Meta: 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 6C8hJnWK 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 mE7oplOZ /YajE6TuBgmwFgE2UzYkdZeVWTOgw8zRUbTxMSm8DlNimJgrUn1/pFVZNAUavlpylTk0wrjhTbL3l2zX8f3M2ADUVf6iBCDxV7iOK41eXdvhP/zai8+RTeiakTJ2qKyyxfj7SuYvx0wTCSU45raGr9xlcxVnD+kWI/XYMW/w52k2AJ4IOUl+mEKFsnderUZcKRNAiIuar5Te9sDg+ZTqCA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Apr 21, 2023 at 7:43=E2=80=AFAM Dmitry Vyukov = wrote: > > On Fri, 21 Apr 2023 at 16:33, syzbot > wrote: > > > > Hello, > > > > syzbot found the following issue on: > > > > HEAD commit: 76f598ba7d8e Merge tag 'for-linus' of git://git.kernel.= org.. > > git tree: upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=3D133bfbedc80= 000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=3D9c5d44636e9= 1081b > > dashboard link: https://syzkaller.appspot.com/bug?extid=3Dc2de99a72baaa= 06d31f3 > > compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for D= ebian) 2.35.2 > > > > Unfortunately, I don't have any reproducer for this issue yet. > > > > Downloadable assets: > > disk image: https://storage.googleapis.com/syzbot-assets/a3654f5f77b9/d= isk-76f598ba.raw.xz > > vmlinux: https://storage.googleapis.com/syzbot-assets/abfb4aaa5772/vmli= nux-76f598ba.xz > > kernel image: https://storage.googleapis.com/syzbot-assets/789fb5546551= /bzImage-76f598ba.xz > > > > IMPORTANT: if you fix the issue, please add the following tag to the co= mmit: > > Reported-by: syzbot+c2de99a72baaa06d31f3@syzkaller.appspotmail.com > > +bpf maintainers > > If I am reading this correctly, this can cause a leak of kernel memory > and/or crash via bpf_get_current_comm helper. > > strcpy() can temporary leave comm buffer non-0 terminated as it > terminates it only after the copy: > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/l= ib/string.c?id=3D76f598ba7d8e2bfb4855b5298caedd5af0c374a8#n184 > > If bpf_get_current_comm() observes such non-0-terminated comm, it will > start reading off bounds. fyi it's using strscpy_pad() in bpf-next. See commit f3f213497797 ("bpf: ensure all memory is initialized in bpf_get_current_comm") but this race might still exist. not sure. > > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > BUG: KCSAN: data-race in strscpy / strscpy > > > > write to 0xffff88812ed8b730 of 8 bytes by task 16157 on cpu 1: > > strscpy+0xa9/0x170 lib/string.c:165 > > strscpy_pad+0x27/0x80 lib/string_helpers.c:835 > > __set_task_comm+0x46/0x140 fs/exec.c:1232 > > set_task_comm include/linux/sched.h:1984 [inline] > > __kthread_create_on_node+0x2b2/0x320 kernel/kthread.c:474 > > kthread_create_on_node+0x8a/0xb0 kernel/kthread.c:512 > > ext4_run_lazyinit_thread fs/ext4/super.c:3848 [inline] > > ext4_register_li_request+0x407/0x650 fs/ext4/super.c:3983 > > __ext4_fill_super fs/ext4/super.c:5480 [inline] > > ext4_fill_super+0x3f4a/0x43f0 fs/ext4/super.c:5637 > > get_tree_bdev+0x2b1/0x3a0 fs/super.c:1303 > > ext4_get_tree+0x1c/0x20 fs/ext4/super.c:5668 > > vfs_get_tree+0x51/0x190 fs/super.c:1510 > > do_new_mount+0x200/0x650 fs/namespace.c:3042 > > path_mount+0x498/0xb40 fs/namespace.c:3372 > > do_mount fs/namespace.c:3385 [inline] > > __do_sys_mount fs/namespace.c:3594 [inline] > > __se_sys_mount+0x27f/0x2d0 fs/namespace.c:3571 > > __x64_sys_mount+0x67/0x80 fs/namespace.c:3571 > > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > > do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 > > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > > > read to 0xffff88812ed8b733 of 1 bytes by task 16161 on cpu 0: > > strscpy+0xde/0x170 lib/string.c:174 > > ____bpf_get_current_comm kernel/bpf/helpers.c:260 [inline] > > bpf_get_current_comm+0x45/0x70 kernel/bpf/helpers.c:252 > > ___bpf_prog_run+0x281/0x3050 kernel/bpf/core.c:1822 > > __bpf_prog_run32+0x74/0xa0 kernel/bpf/core.c:2043 > > bpf_dispatcher_nop_func include/linux/bpf.h:1124 [inline] > > __bpf_prog_run include/linux/filter.h:601 [inline] > > bpf_prog_run include/linux/filter.h:608 [inline] > > __bpf_trace_run kernel/trace/bpf_trace.c:2263 [inline] > > bpf_trace_run4+0x9f/0x140 kernel/trace/bpf_trace.c:2304 > > __traceiter_sched_switch+0x3a/0x50 include/trace/events/sched.h:222 > > trace_sched_switch include/trace/events/sched.h:222 [inline] > > __schedule+0x7e7/0x8e0 kernel/sched/core.c:6622 > > schedule+0x51/0x80 kernel/sched/core.c:6701 > > schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:6760 > > kthread+0x11c/0x1e0 kernel/kthread.c:369 > > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308 > > > > value changed: 0x72 -> 0x34 > > > > Reported by Kernel Concurrency Sanitizer on: > > CPU: 0 PID: 16161 Comm: ext4lazyinit Not tainted 6.3.0-rc5-syzkaller-00= 022-g76f598ba7d8e #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS= Google 03/30/2023 > > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > > > > > --- > > This report is generated by a bot. It may contain errors. > > See https://goo.gl/tpsmEJ for more information about syzbot. > > syzbot engineers can be reached at syzkaller@googlegroups.com. > > > > syzbot will keep track of this issue. See: > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.