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Message-ID: <CAG_fn=Uxaq1juuq-3cA1qQu6gB7ZB=LpyxBEdKf7DpYfAo3zmg@mail.gmail.com> Date: Tue, 16 Apr 2024 10:52:12 +0200 From: Alexander Potapenko <glider@...gle.com> To: Alexei Starovoitov <alexei.starovoitov@...il.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, syzbot <syzbot+79102ed905e5b2dc0fc3@...kaller.appspotmail.com>, LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>, syzkaller-bugs <syzkaller-bugs@...glegroups.com>, bpf <bpf@...r.kernel.org> Subject: Re: [syzbot] [mm?] KMSAN: kernel-infoleak in bpf_probe_write_user On Mon, Apr 15, 2024 at 11:06 PM Alexei Starovoitov <alexei.starovoitov@...il.com> wrote: > > Hi, > > syzbot folks, please disable such "bug" reporting. > The whole point of bpf is to pass such info to userspace. > probe_write_user, various ring buffers, bpf_*_printk-s, bpf maps > all serve this purpose of "infoleak". > Hi Alexei, >From KMSAN's perspective it is fine to pass information to the userspace, unless it is marked as uninitialized. It could be that we are missing some initialization in kernel/bpf/core.c though. Do you know which part of the code is supposed to initialize the stack in PROG_NAME? > On Mon, Apr 15, 2024 at 1:18 PM Andrew Morton <akpm@...ux-foundation.org> wrote: > > > > (cc bpf@) > > > > On Fri, 12 Apr 2024 19:27:25 -0700 syzbot <syzbot+79102ed905e5b2dc0fc3@...kaller.appspotmail.com> wrote: > > > > > Hello, > > > > > > syzbot found the following issue on: > > > > > > HEAD commit: fec50db7033e Linux 6.9-rc3 > > > git tree: upstream > > > console+strace: https://syzkaller.appspot.com/x/log.txt?x=16509ba1180000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=13e7da432565d94c > > > dashboard link: https://syzkaller.appspot.com/bug?extid=79102ed905e5b2dc0fc3 > > > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 > > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10a4af9d180000 > > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12980f9d180000 > > > > > > Downloadable assets: > > > disk image: https://storage.googleapis.com/syzbot-assets/901017b36ccc/disk-fec50db7.raw.xz > > > vmlinux: https://storage.googleapis.com/syzbot-assets/16bfcf5618d3/vmlinux-fec50db7.xz > > > kernel image: https://storage.googleapis.com/syzbot-assets/dc9c5a1e7d02/bzImage-fec50db7.xz > > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > > Reported-by: syzbot+79102ed905e5b2dc0fc3@...kaller.appspotmail.com > > > > > > ===================================================== > > > BUG: KMSAN: kernel-infoleak in instrument_copy_to_user include/linux/instrumented.h:114 [inline] > > > BUG: KMSAN: kernel-infoleak in __copy_to_user_inatomic include/linux/uaccess.h:125 [inline] > > > BUG: KMSAN: kernel-infoleak in copy_to_user_nofault+0x129/0x1f0 mm/maccess.c:149 > > > instrument_copy_to_user include/linux/instrumented.h:114 [inline] > > > __copy_to_user_inatomic include/linux/uaccess.h:125 [inline] > > > copy_to_user_nofault+0x129/0x1f0 mm/maccess.c:149 > > > ____bpf_probe_write_user kernel/trace/bpf_trace.c:349 [inline] > > > bpf_probe_write_user+0x104/0x180 kernel/trace/bpf_trace.c:327 > > > ___bpf_prog_run+0x13fe/0xe0f0 kernel/bpf/core.c:1997 > > > __bpf_prog_run64+0xb5/0xe0 kernel/bpf/core.c:2236 > > > bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline] > > > __bpf_prog_run include/linux/filter.h:657 [inline] > > > bpf_prog_run include/linux/filter.h:664 [inline] > > > __bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline] > > > bpf_trace_run2+0x116/0x300 kernel/trace/bpf_trace.c:2420 > > > __bpf_trace_kfree+0x29/0x40 include/trace/events/kmem.h:94 > > > trace_kfree include/trace/events/kmem.h:94 [inline] > > > kfree+0x6a5/0xa30 mm/slub.c:4377 > > > vfs_writev+0x12bf/0x1450 fs/read_write.c:978 > > > do_writev+0x251/0x5c0 fs/read_write.c:1018 > > > __do_sys_writev fs/read_write.c:1091 [inline] > > > __se_sys_writev fs/read_write.c:1088 [inline] > > > __x64_sys_writev+0x98/0xe0 fs/read_write.c:1088 > > > do_syscall_64+0xd5/0x1f0 > > > entry_SYSCALL_64_after_hwframe+0x72/0x7a > > > > > > Local variable stack created at: > > > __bpf_prog_run64+0x45/0xe0 kernel/bpf/core.c:2236 > > > bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline] > > > __bpf_prog_run include/linux/filter.h:657 [inline] > > > bpf_prog_run include/linux/filter.h:664 [inline] > > > __bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline] > > > bpf_trace_run2+0x116/0x300 kernel/trace/bpf_trace.c:2420 > > > > > > Bytes 0-7 of 8 are uninitialized > > > Memory access of size 8 starts at ffff888121ec7ae8 > > > Data copied to user address 00000000ffffffff > > > > > > CPU: 1 PID: 4779 Comm: dhcpcd Not tainted 6.9.0-rc3-syzkaller #0 > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024 > > > ===================================================== > > > > > > > > > --- > > > 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@...glegroups.com. > > > > > > syzbot will keep track of this issue. See: > > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > > > > > If the report is already addressed, let syzbot know by replying with: > > > #syz fix: exact-commit-title > > > > > > If you want syzbot to run the reproducer, reply with: > > > #syz test: git://repo/address.git branch-or-commit-hash > > > If you attach or paste a git patch, syzbot will apply it before testing. > > > > > > If you want to overwrite report's subsystems, reply with: > > > #syz set subsystems: new-subsystem > > > (See the list of subsystem names on the web dashboard) > > > > > > If the report is a duplicate of another one, reply with: > > > #syz dup: exact-subject-of-another-report > > > > > > If you want to undo deduplication, reply with: > > > #syz undup > > > > -- > You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@...glegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/CAADnVQ%2BE%3Dj1Z4MOuk2f-U33oqvUmmrRcvWvsDrmLXvD8FhUmsQ%40mail.gmail.com. -- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Paul Manicle, Liana Sebastian Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg
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