On Mon, 24 Apr 2023 at 09:19, syzbot <syzbot+4a03518df1e31b537066@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > Hello, > > syzbot found the following issue on: > > HEAD commit: 44149752e998 Merge tag 'cgroup-for-6.3-rc6-fixes' of git:/.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=100db37bc80000 > kernel config: https://syzkaller.appspot.com/x/.config?x=710057cbb8def08c > dashboard link: https://syzkaller.appspot.com/bug?extid=4a03518df1e31b537066 > compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2 > > Unfortunately, I don't have any reproducer for this issue yet. > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/7bfa303f05cc/disk-44149752.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/4e8ea8730409/vmlinux-44149752.xz > kernel image: https://storage.googleapis.com/syzbot-assets/e584bce13ba7/bzImage-44149752.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+4a03518df1e31b537066@xxxxxxxxxxxxxxxxxxxxxxxxx The race is here: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/ext4/extents_status.c?id=44149752e9987a9eac5ad78e6d3a20934b5e018d#n271 If I am reading this correctly, it can lead to returning a wrong extent if tree->cache_es is re-read after the range check. I think tree->cache_es read/write should use READ/WRITE_ONCE. > ================================================================== > BUG: KCSAN: data-race in __es_find_extent_range / __es_find_extent_range > > write to 0xffff88810a5a98a8 of 8 bytes by task 10666 on cpu 0: > __es_find_extent_range+0x212/0x300 fs/ext4/extents_status.c:296 > ext4_es_find_extent_range+0x91/0x260 fs/ext4/extents_status.c:318 > ext4_ext_put_gap_in_cache fs/ext4/extents.c:2284 [inline] > ext4_ext_map_blocks+0x120d/0x36c0 fs/ext4/extents.c:4191 > ext4_map_blocks+0x2a0/0x1050 fs/ext4/inode.c:576 > ext4_mpage_readpages+0x699/0x1440 fs/ext4/readpage.c:300 > ext4_read_folio+0xc5/0x1a0 fs/ext4/inode.c:3308 > filemap_read_folio+0x2c/0x100 mm/filemap.c:2424 > filemap_fault+0x66f/0xb20 mm/filemap.c:3367 > __do_fault mm/memory.c:4155 [inline] > do_read_fault mm/memory.c:4506 [inline] > do_fault mm/memory.c:4635 [inline] > handle_pte_fault mm/memory.c:4923 [inline] > __handle_mm_fault mm/memory.c:5065 [inline] > handle_mm_fault+0x115d/0x21d0 mm/memory.c:5211 > faultin_page mm/gup.c:925 [inline] > __get_user_pages+0x363/0xc30 mm/gup.c:1147 > populate_vma_page_range mm/gup.c:1543 [inline] > __mm_populate+0x23a/0x360 mm/gup.c:1652 > mm_populate include/linux/mm.h:3026 [inline] > vm_mmap_pgoff+0x174/0x210 mm/util.c:547 > ksys_mmap_pgoff+0x2ac/0x320 mm/mmap.c:1410 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > read to 0xffff88810a5a98a8 of 8 bytes by task 10630 on cpu 1: > __es_find_extent_range+0x79/0x300 fs/ext4/extents_status.c:270 > __es_scan_range fs/ext4/extents_status.c:345 [inline] > __es_scan_clu fs/ext4/extents_status.c:399 [inline] > ext4_es_scan_clu+0xe4/0x190 fs/ext4/extents_status.c:415 > ext4_insert_delayed_block fs/ext4/inode.c:1694 [inline] > ext4_da_map_blocks fs/ext4/inode.c:1806 [inline] > ext4_da_get_block_prep+0x575/0xa70 fs/ext4/inode.c:1870 > __block_write_begin_int+0x349/0xe50 fs/buffer.c:2034 > __block_write_begin+0x5e/0x110 fs/buffer.c:2084 > ext4_da_write_begin+0x2fa/0x610 fs/ext4/inode.c:3084 > generic_perform_write+0x1c3/0x3d0 mm/filemap.c:3926 > ext4_buffered_write_iter+0x234/0x3e0 fs/ext4/file.c:289 > ext4_file_write_iter+0xd7/0x10e0 > call_write_iter include/linux/fs.h:1851 [inline] > new_sync_write fs/read_write.c:491 [inline] > vfs_write+0x463/0x760 fs/read_write.c:584 > ksys_write+0xeb/0x1a0 fs/read_write.c:637 > __do_sys_write fs/read_write.c:649 [inline] > __se_sys_write fs/read_write.c:646 [inline] > __x64_sys_write+0x42/0x50 fs/read_write.c:646 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > value changed: 0xffff88810a653dc0 -> 0xffff8881067334d8 > > Reported by Kernel Concurrency Sanitizer on: > CPU: 1 PID: 10630 Comm: syz-executor.0 Not tainted 6.3.0-rc6-syzkaller-00138-g44149752e998 #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023 > ================================================================== > > > --- > 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.
