On Sat, Jun 8, 2024 at 2:09 PM syzbot <syzbot+9c1fe13fcb51574b249b@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > Hello, > > syzbot found the following issue on: > > HEAD commit: 614da38e2f7a Merge tag 'hid-for-linus-2024051401' of git:/.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=113f3fd6980000 > kernel config: https://syzkaller.appspot.com/x/.config?x=f5d2cbf33633f507 > dashboard link: https://syzkaller.appspot.com/bug?extid=9c1fe13fcb51574b249b > 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/89eafb874b71/disk-614da38e.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/356000512ad9/vmlinux-614da38e.xz > kernel image: https://storage.googleapis.com/syzbot-assets/839c73939115/bzImage-614da38e.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+9c1fe13fcb51574b249b@xxxxxxxxxxxxxxxxxxxxxxxxx This doesn't look like a zswap bug, and perhaps not a bug at all but I am not sure. Zswap is reading the data in a folio to check if it is filled with a repeated pattern, and it is encountering uninitialized data. I am not sure if this is expected behavior or not. Could it just be that the size of the data written by syzbot is not divisible by PAGE_SIZE, so part of the final page is left uninitialized? Do we keep the unwritten parts of a shmem page uninitialized by any chance? Hugh, do you mind taking a quick look at whether this is a real bug? If this is expected behavior, perhaps there is some annotation we can use in zswap that it is fine to encounter uninitialized data when reading the folio. > > ===================================================== > BUG: KMSAN: uninit-value in zswap_is_page_same_filled mm/zswap.c:1481 [inline] > BUG: KMSAN: uninit-value in zswap_store+0x1008/0x2ca0 mm/zswap.c:1553 > zswap_is_page_same_filled mm/zswap.c:1481 [inline] > zswap_store+0x1008/0x2ca0 mm/zswap.c:1553 > swap_writepage+0x126/0x4c0 mm/page_io.c:198 > shmem_writepage+0x1826/0x1f70 mm/shmem.c:1518 > pageout mm/vmscan.c:660 [inline] > shrink_folio_list+0x4a55/0x7910 mm/vmscan.c:1323 > evict_folios+0x9d7f/0xcc20 mm/vmscan.c:4537 > try_to_shrink_lruvec+0x160e/0x1a50 mm/vmscan.c:4733 > shrink_one+0x66f/0xd40 mm/vmscan.c:4772 > shrink_many mm/vmscan.c:4835 [inline] > lru_gen_shrink_node mm/vmscan.c:4935 [inline] > shrink_node+0x4856/0x55f0 mm/vmscan.c:5894 > kswapd_shrink_node mm/vmscan.c:6704 [inline] > balance_pgdat mm/vmscan.c:6895 [inline] > kswapd+0x1eba/0x4460 mm/vmscan.c:7164 > kthread+0x3e2/0x540 kernel/kthread.c:389 > ret_from_fork+0x6d/0x90 arch/x86/kernel/process.c:147 > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 > > Uninit was stored to memory at: > memcpy_from_iter lib/iov_iter.c:73 [inline] > iterate_bvec include/linux/iov_iter.h:122 [inline] > iterate_and_advance2 include/linux/iov_iter.h:249 [inline] > iterate_and_advance include/linux/iov_iter.h:271 [inline] > __copy_from_iter lib/iov_iter.c:249 [inline] > copy_page_from_iter_atomic+0x12b7/0x2ae0 lib/iov_iter.c:481 > generic_perform_write+0x4c1/0xc60 mm/filemap.c:3982 > shmem_file_write_iter+0x2bd/0x2f0 mm/shmem.c:2920 > do_iter_readv_writev+0x7e6/0x960 > vfs_iter_write+0x459/0xd00 fs/read_write.c:895 > lo_write_bvec drivers/block/loop.c:246 [inline] > lo_write_simple drivers/block/loop.c:267 [inline] > do_req_filebacked drivers/block/loop.c:491 [inline] > loop_handle_cmd drivers/block/loop.c:1907 [inline] > loop_process_work+0x1502/0x3440 drivers/block/loop.c:1942 > loop_rootcg_workfn+0x2b/0x40 drivers/block/loop.c:1973 > process_one_work kernel/workqueue.c:3267 [inline] > process_scheduled_works+0xa81/0x1bd0 kernel/workqueue.c:3348 > worker_thread+0xea5/0x1560 kernel/workqueue.c:3429 > kthread+0x3e2/0x540 kernel/kthread.c:389 > ret_from_fork+0x6d/0x90 arch/x86/kernel/process.c:147 > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 > > Uninit was created at: > __alloc_pages+0x9d6/0xe70 mm/page_alloc.c:4598 > alloc_pages_mpol+0x299/0x990 mm/mempolicy.c:2264 > alloc_pages mm/mempolicy.c:2335 [inline] > folio_alloc+0x1d0/0x230 mm/mempolicy.c:2342 > filemap_alloc_folio+0xa6/0x440 mm/filemap.c:984 > __filemap_get_folio+0xa10/0x14b0 mm/filemap.c:1926 > grow_dev_folio fs/buffer.c:1042 [inline] > grow_buffers fs/buffer.c:1108 [inline] > __getblk_slow fs/buffer.c:1134 [inline] > bdev_getblk+0x39b/0xc80 fs/buffer.c:1429 > __getblk include/linux/buffer_head.h:355 [inline] > sb_getblk include/linux/buffer_head.h:361 [inline] > ext4_getblk+0x3da/0xe00 fs/ext4/inode.c:843 > ext4_xattr_inode_write fs/ext4/xattr.c:1421 [inline] > ext4_xattr_inode_lookup_create fs/ext4/xattr.c:1596 [inline] > ext4_xattr_set_entry+0x574d/0x6880 fs/ext4/xattr.c:1718 > ext4_xattr_block_set+0xb94/0x4fb0 fs/ext4/xattr.c:2037 > ext4_xattr_move_to_block fs/ext4/xattr.c:2654 [inline] > ext4_xattr_make_inode_space fs/ext4/xattr.c:2729 [inline] > ext4_expand_extra_isize_ea+0x20bd/0x3560 fs/ext4/xattr.c:2821 > __ext4_expand_extra_isize+0x5dc/0x680 fs/ext4/inode.c:5789 > ext4_try_to_expand_extra_isize fs/ext4/inode.c:5832 [inline] > __ext4_mark_inode_dirty+0x70d/0xa10 fs/ext4/inode.c:5910 > ext4_delete_inline_entry+0x650/0x7d0 fs/ext4/inline.c:1753 > ext4_delete_entry+0x13f/0x7d0 fs/ext4/namei.c:2719 > __ext4_unlink+0x9b8/0x11b0 fs/ext4/namei.c:3273 > ext4_unlink+0x226/0x630 fs/ext4/namei.c:3321 > vfs_unlink+0x676/0xa30 fs/namei.c:4343 > do_unlinkat+0x823/0xe10 fs/namei.c:4407 > __do_sys_unlinkat fs/namei.c:4450 [inline] > __se_sys_unlinkat fs/namei.c:4443 [inline] > __x64_sys_unlinkat+0x17c/0x230 fs/namei.c:4443 > x64_sys_call+0x846/0x3b50 arch/x86/include/generated/asm/syscalls_64.h:264 > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > CPU: 1 PID: 88 Comm: kswapd1 Not tainted 6.9.0-syzkaller-02707-g614da38e2f7a #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024 > ===================================================== > > > --- > 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
