On Mon, Oct 14, 2024 at 11:08 AM syzbot <syzbot+b79be83906cd9bab16ff@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > Hello, > > syzbot found the following issue on: > > HEAD commit: 2f91ff27b0ee Merge tag 'sound-6.12-rc2' of git://git.kerne.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=155c879f980000 > kernel config: https://syzkaller.appspot.com/x/.config?x=95098faba89c70c9 > dashboard link: https://syzkaller.appspot.com/bug?extid=b79be83906cd9bab16ff > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 > > Unfortunately, I don't have any reproducer for this issue yet. > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/14933c4ac457/disk-2f91ff27.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/6725831fc1a1/vmlinux-2f91ff27.xz > kernel image: https://storage.googleapis.com/syzbot-assets/98d64e038e72/bzImage-2f91ff27.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+b79be83906cd9bab16ff@xxxxxxxxxxxxxxxxxxxxxxxxx > > loop4: detected capacity change from 0 to 4096 > EXT4-fs: Ignoring removed nobh option > EXT4-fs: Ignoring removed i_version option > ================================================================== > BUG: KCSAN: data-race in xas_create / xas_find > > write to 0xffff888106819919 of 1 bytes by task 3435 on cpu 0: > xas_expand lib/xarray.c:613 [inline] > xas_create+0x666/0xbd0 lib/xarray.c:654 > xas_store+0x6f/0xc90 lib/xarray.c:788 AFAIU, xas_store() itself, doesn't have a locking mechanism, but is locked in xa_* functions. Example: void *xa_store_range(...) { XA_STATE(xas, xa, 0); ... do { xas_lock(&xas); if (entry) { ... xas_create(&xas, true); } ... unlock: xas_unlock(&xas); } Same thing is for the another racing xas_find() function: void *xa_find(...) { XA_STATE(xas, xa, *indexp); void *entry; rcu_read_lock(); do { if (...) entry = xas_find_marked(&xas, max, filter); else entry = xas_find(&xas, max); ... rcu_read_unlock(); } In this KCSAN report, xas_create() and xas_find() are racing for `offset` field. > __filemap_add_folio+0x3cc/0x6f0 mm/filemap.c:916 > filemap_add_folio+0x9c/0x1b0 mm/filemap.c:972 > page_cache_ra_unbounded+0x175/0x310 mm/readahead.c:268 > do_page_cache_ra mm/readahead.c:320 [inline] > force_page_cache_ra mm/readahead.c:349 [inline] > page_cache_sync_ra+0x252/0x670 mm/readahead.c:562 > page_cache_sync_readahead include/linux/pagemap.h:1394 [inline] > filemap_get_pages+0x2c1/0x10e0 mm/filemap.c:2547 > filemap_read+0x216/0x680 mm/filemap.c:2645 > blkdev_read_iter+0x20e/0x2c0 block/fops.c:765 > new_sync_read fs/read_write.c:488 [inline] > vfs_read+0x5f6/0x720 fs/read_write.c:569 > ksys_read+0xeb/0x1b0 fs/read_write.c:712 > __do_sys_read fs/read_write.c:722 [inline] > __se_sys_read fs/read_write.c:720 [inline] > __x64_sys_read+0x42/0x50 fs/read_write.c:720 > x64_sys_call+0x27d3/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:1 > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > read to 0xffff888106819919 of 1 bytes by task 9109 on cpu 1: > xas_find+0x372/0x3f0 lib/xarray.c:1278 > find_get_entry+0x66/0x390 mm/filemap.c:1992 > find_get_entries+0xa4/0x220 mm/filemap.c:2047 > truncate_inode_pages_range+0x4ac/0x6b0 mm/truncate.c:378 > truncate_inode_pages+0x24/0x30 mm/truncate.c:423 > kill_bdev block/bdev.c:91 [inline] > set_blocksize+0x258/0x270 block/bdev.c:173 > sb_set_blocksize block/bdev.c:182 [inline] > sb_min_blocksize+0x63/0xe0 block/bdev.c:198 > ext4_load_super fs/ext4/super.c:4992 [inline] > __ext4_fill_super fs/ext4/super.c:5213 [inline] > ext4_fill_super+0x38b/0x3a10 fs/ext4/super.c:5686 > get_tree_bdev+0x256/0x2e0 fs/super.c:1635 > ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5718 > vfs_get_tree+0x56/0x1e0 fs/super.c:1800 > do_new_mount+0x227/0x690 fs/namespace.c:3507 > path_mount+0x49b/0xb30 fs/namespace.c:3834 > do_mount fs/namespace.c:3847 [inline] > __do_sys_mount fs/namespace.c:4055 [inline] > __se_sys_mount+0x27c/0x2d0 fs/namespace.c:4032 > __x64_sys_mount+0x67/0x80 fs/namespace.c:4032 > x64_sys_call+0x203e/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:166 > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > value changed: 0x0e -> 0x00 > > Reported by Kernel Concurrency Sanitizer on: > CPU: 1 UID: 0 PID: 9109 Comm: syz.4.1794 Not tainted 6.12.0-rc1-syzkaller-00257-g2f91ff27b0ee #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 > ================================================================== > EXT4-fs (loop4): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: writeback. > EXT4-fs (loop4): unmounting filesystem 00000000-0000-0000-0000-000000000000. > > > --- > 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@xxxxxxxxxxxxxxxx. > > 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 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 >
