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 ?
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_run5+0x16f/0x350 kernel/trace/bpf_trace.c:2423
__bpf_trace_ext4_remove_blocks+0x45/0x60 include/trace/events/ext4.h:1984
__traceiter_ext4_remove_blocks+0xb5/0x170 include/trace/events/ext4.h:1984
trace_ext4_remove_blocks include/trace/events/ext4.h:1984 [inline]
ext4_remove_blocks fs/ext4/extents.c:2463 [inline]
ext4_ext_rm_leaf fs/ext4/extents.c:2686 [inline]
ext4_ext_remove_space+0x4e30/0x7e00 fs/ext4/extents.c:2934
ext4_ext_truncate+0x1e3/0x390 fs/ext4/extents.c:4440
ext4_truncate+0x14c6/0x1e10 fs/ext4/inode.c:4146
ext4_evict_inode+0x1886/0x24d0 fs/ext4/inode.c:258
evict+0x3ae/0xa60 fs/inode.c:667
iput_final fs/inode.c:1741 [inline]
iput+0x9ca/0xe10 fs/inode.c:1767
d_delete_notify include/linux/fsnotify.h:307 [inline]
vfs_rmdir+0x53c/0x790 fs/namei.c:4222
do_rmdir+0x630/0x8b0 fs/namei.c:4268
__do_sys_rmdir fs/namei.c:4287 [inline]
__se_sys_rmdir fs/namei.c:4285 [inline]
__x64_sys_rmdir+0x78/0xb0 fs/namei.c:4285
do_syscall_64+0xd5/0x1f0
entry_SYSCALL_64_after_hwframe+0x6d/0x75
Local variable stack created at:
__bpf_prog_run256+0x45/0xe0 kernel/bpf/core.c:2237
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_run5+0x16f/0x350 kernel/trace/bpf_trace.c:2423
CPU: 0 PID: 5017 Comm: syz-executor365 Not tainted 6.8.0-syzkaller-13236-g5e74df2f8f15 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
=====================================================
