On Sun 04-02-24 03:44:30, syzbot wrote: > syzbot has found a reproducer for the following issue on: > > HEAD commit: 9f8413c4a66f Merge tag 'cgroup-for-6.8' of git://git.kerne.. > git tree: upstream > console+strace: https://syzkaller.appspot.com/x/log.txt?x=10fcfdc0180000 > kernel config: https://syzkaller.appspot.com/x/.config?x=656820e61b758b15 > dashboard link: https://syzkaller.appspot.com/bug?extid=3ce5dea5b1539ff36769 > 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=139dd53fe80000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12685aa8180000 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/79d9f2f4b065/disk-9f8413c4.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/cbc68430d9c6/vmlinux-9f8413c4.xz > kernel image: https://storage.googleapis.com/syzbot-assets/9740ad9fc172/bzImage-9f8413c4.xz > mounted in repro: https://storage.googleapis.com/syzbot-assets/25f4008bd752/mount_0.gz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+3ce5dea5b1539ff36769@xxxxxxxxxxxxxxxxxxxxxxxxx > > ===================================================== > BUG: KMSAN: uninit-value in memcmp lib/string.c:692 [inline] > BUG: KMSAN: uninit-value in bcmp+0x186/0x1c0 lib/string.c:713 > memcmp lib/string.c:692 [inline] > bcmp+0x186/0x1c0 lib/string.c:713 > fanotify_fh_equal fs/notify/fanotify/fanotify.c:51 [inline] So I'm not sure how this is possible. In fanotify_encode_fh() we have: dwords = fh_len >> 2; type = exportfs_encode_fid(inode, buf, &dwords); err = -EINVAL; if (type <= 0 || type == FILEID_INVALID || fh_len != dwords << 2) goto out_err; fh->type = type; fh->len = fh_len; So if the encoded file handle was different length than what we expected we will fail the creation of the event... Aha, the FAT filesystem is mounted in nfs=nostale_ro which means that we're using fat_export_ops_nostale and thus fat_encode_fh_nostale for encoding fh. And FAT_FID_SIZE_WITHOUT_PARENT is 3 (i.e. 12 bytes) but the function initializes just the first 10 bytes of struct fat_fid. I'll send a fix for FAT. Honza > fanotify_fid_event_equal fs/notify/fanotify/fanotify.c:72 [inline] > fanotify_should_merge fs/notify/fanotify/fanotify.c:168 [inline] > fanotify_merge+0x15f5/0x27e0 fs/notify/fanotify/fanotify.c:209 > fsnotify_insert_event+0x1d0/0x600 fs/notify/notification.c:113 > fanotify_handle_event+0x47f7/0x6140 fs/notify/fanotify/fanotify.c:966 > send_to_group fs/notify/fsnotify.c:360 [inline] > fsnotify+0x2510/0x3530 fs/notify/fsnotify.c:570 > fsnotify_parent include/linux/fsnotify.h:80 [inline] > fsnotify_file include/linux/fsnotify.h:100 [inline] > fsnotify_close include/linux/fsnotify.h:362 [inline] > __fput+0x578/0x10c0 fs/file_table.c:368 > __fput_sync+0x74/0x90 fs/file_table.c:467 > __do_sys_close fs/open.c:1554 [inline] > __se_sys_close+0x28a/0x4c0 fs/open.c:1539 > __x64_sys_close+0x48/0x60 fs/open.c:1539 > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > do_syscall_64+0x6d/0x140 arch/x86/entry/common.c:83 > entry_SYSCALL_64_after_hwframe+0x63/0x6b > > Uninit was created at: > slab_post_alloc_hook+0x129/0xa70 mm/slab.h:768 > slab_alloc_node mm/slub.c:3478 [inline] > slab_alloc mm/slub.c:3486 [inline] > __kmem_cache_alloc_lru mm/slub.c:3493 [inline] > kmem_cache_alloc+0x579/0xa90 mm/slub.c:3502 > fanotify_alloc_fid_event fs/notify/fanotify/fanotify.c:584 [inline] > fanotify_alloc_event fs/notify/fanotify/fanotify.c:817 [inline] > fanotify_handle_event+0x2ff6/0x6140 fs/notify/fanotify/fanotify.c:952 > send_to_group fs/notify/fsnotify.c:360 [inline] > fsnotify+0x2510/0x3530 fs/notify/fsnotify.c:570 > fsnotify_parent include/linux/fsnotify.h:80 [inline] > fsnotify_file include/linux/fsnotify.h:100 [inline] > fsnotify_close include/linux/fsnotify.h:362 [inline] > __fput+0x578/0x10c0 fs/file_table.c:368 > __fput_sync+0x74/0x90 fs/file_table.c:467 > __do_sys_close fs/open.c:1554 [inline] > __se_sys_close+0x28a/0x4c0 fs/open.c:1539 > __x64_sys_close+0x48/0x60 fs/open.c:1539 > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > do_syscall_64+0x6d/0x140 arch/x86/entry/common.c:83 > entry_SYSCALL_64_after_hwframe+0x63/0x6b > > CPU: 0 PID: 5010 Comm: syz-executor120 Not tainted 6.7.0-syzkaller-00562-g9f8413c4a66f #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024 > ===================================================== > > > --- > 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. > -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
