On Tue, Mar 26, 2024 at 5:54 PM Martin KaFai Lau <martin.lau@xxxxxxxxx> wrote: > > On 3/25/24 2:36 AM, syzbot wrote: > > Hello, > > > > syzbot found the following issue on: > > > > HEAD commit: 5e74df2f8f15 Merge tag 'x86-urgent-2024-03-24' of git://gi.. > > git tree: upstream > > console+strace: https://syzkaller.appspot.com/x/log.txt?x=148872a5180000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=e6bd769cb793b98a > > dashboard link: https://syzkaller.appspot.com/bug?extid=1a3cf6f08d68868f9db3 > > 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=15921a6e180000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12e081f1180000 > > > > Downloadable assets: > > disk image: https://storage.googleapis.com/syzbot-assets/1a82880723a7/disk-5e74df2f.raw.xz > > vmlinux: https://storage.googleapis.com/syzbot-assets/fd3046ac43b9/vmlinux-5e74df2f.xz > > kernel image: https://storage.googleapis.com/syzbot-assets/2097be59cbc1/bzImage-5e74df2f.xz > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > Reported-by: syzbot+1a3cf6f08d68868f9db3@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > ===================================================== > > BUG: KMSAN: uninit-value in __dev_map_lookup_elem kernel/bpf/devmap.c:441 [inline] > > BUG: KMSAN: uninit-value in dev_map_lookup_elem+0xf3/0x170 kernel/bpf/devmap.c:796 > > __dev_map_lookup_elem kernel/bpf/devmap.c:441 [inline] > > dev_map_lookup_elem+0xf3/0x170 kernel/bpf/devmap.c:796 > > ____bpf_map_lookup_elem kernel/bpf/helpers.c:42 [inline] > > bpf_map_lookup_elem+0x5c/0x80 kernel/bpf/helpers.c:38 > > ___bpf_prog_run+0x13fe/0xe0f0 kernel/bpf/core.c:1997 > > __bpf_prog_run256+0xb5/0xe0 kernel/bpf/core.c:2237 > > It should be in the interpreter mode. > > The C reproducer is trying to run the following bpf prog: > > 0: (18) r0 = 0x0 > 2: (18) r1 = map[id:49] > 4: (b7) r8 = 16777216 > 5: (7b) *(u64 *)(r10 -8) = r8 > 6: (bf) r2 = r10 > 7: (07) r2 += -229 > ^^^^^^^^^^ > > 8: (b7) r3 = 8 > 9: (b7) r4 = 0 > 10: (85) call dev_map_lookup_elem#1543472 > 11: (95) exit > > I think this KMSAN report (and a few others related to lookup/delete_elem) > should only happen in the interpreter mode. > > Does it worth to suppress it by always initializing the stack in the interpreter > mode considering the interpreter is not very speed sensitive ? Maybe we can mark it as initialized from kmsan pov ? There are kasan_poison/unpoison helpers that may fit ?
