On Sat, Apr 6, 2024 at 8:00 PM syzbot <syzbot+47a017c46edb25eff048@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > syzbot has found a reproducer for the following issue on: > > HEAD commit: e8b0ccb2a787 Merge tag '9p-for-6.9-rc3' of https://github... > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=115eb623180000 > kernel config: https://syzkaller.appspot.com/x/.config?x=5112b3f484393436 > dashboard link: https://syzkaller.appspot.com/bug?extid=47a017c46edb25eff048 > 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=156679a1180000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10f27ef6180000 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/cf4b0d1e3b2d/disk-e8b0ccb2.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/422cac6cc940/vmlinux-e8b0ccb2.xz > kernel image: https://storage.googleapis.com/syzbot-assets/9a4df48e199b/bzImage-e8b0ccb2.xz > mounted in repro: https://storage.googleapis.com/syzbot-assets/69e1e69e7522/mount_0.gz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+47a017c46edb25eff048@xxxxxxxxxxxxxxxxxxxxxxxxx > > ===================================================== > BUG: KMSAN: uninit-value in crc32_body lib/crc32.c:110 [inline] > BUG: KMSAN: uninit-value in crc32_le_generic lib/crc32.c:179 [inline] > BUG: KMSAN: uninit-value in crc32_le_base+0x43c/0xd80 lib/crc32.c:197 > crc32_body lib/crc32.c:110 [inline] > crc32_le_generic lib/crc32.c:179 [inline] > crc32_le_base+0x43c/0xd80 lib/crc32.c:197 > nilfs_segbuf_fill_in_data_crc fs/nilfs2/segbuf.c:224 [inline] > nilfs_add_checksums_on_logs+0xb80/0xe40 fs/nilfs2/segbuf.c:327 > nilfs_segctor_do_construct+0x9876/0xdeb0 fs/nilfs2/segment.c:2078 > nilfs_segctor_construct+0x1eb/0xe30 fs/nilfs2/segment.c:2381 > nilfs_segctor_thread_construct fs/nilfs2/segment.c:2489 [inline] > nilfs_segctor_thread+0xc50/0x11e0 fs/nilfs2/segment.c:2573 > kthread+0x3e2/0x540 kernel/kthread.c:388 > ret_from_fork+0x6d/0x90 arch/x86/kernel/process.c:147 > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243 > > 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+0x12b7/0x2b60 lib/iov_iter.c:481 > generic_perform_write+0x4c1/0xc60 mm/filemap.c:3982 > __generic_file_write_iter+0x20a/0x460 mm/filemap.c:4069 > generic_file_write_iter+0x103/0x5b0 mm/filemap.c:4095 > __kernel_write_iter+0x68b/0xc40 fs/read_write.c:523 > dump_emit_page fs/coredump.c:890 [inline] > dump_user_range+0x8dc/0xee0 fs/coredump.c:951 > elf_core_dump+0x520f/0x59c0 fs/binfmt_elf.c:2077 > do_coredump+0x32d5/0x4920 fs/coredump.c:764 > get_signal+0x267e/0x2d00 kernel/signal.c:2896 > arch_do_signal_or_restart+0x53/0xcb0 arch/x86/kernel/signal.c:310 > exit_to_user_mode_loop kernel/entry/common.c:111 [inline] > exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline] > __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] > syscall_exit_to_user_mode+0x5d/0x160 kernel/entry/common.c:218 > do_syscall_64+0xe4/0x1f0 arch/x86/entry/common.c:89 > entry_SYSCALL_64_after_hwframe+0x72/0x7a > > Uninit was created at: > __alloc_pages+0x9d6/0xe70 mm/page_alloc.c:4598 > alloc_pages_mpol+0x299/0x990 mm/mempolicy.c:2264 > alloc_pages+0x1bf/0x1e0 mm/mempolicy.c:2335 > dump_user_range+0x4a/0xee0 fs/coredump.c:935 > elf_core_dump+0x520f/0x59c0 fs/binfmt_elf.c:2077 > do_coredump+0x32d5/0x4920 fs/coredump.c:764 > get_signal+0x267e/0x2d00 kernel/signal.c:2896 > arch_do_signal_or_restart+0x53/0xcb0 arch/x86/kernel/signal.c:310 > exit_to_user_mode_loop kernel/entry/common.c:111 [inline] > exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline] > __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] > syscall_exit_to_user_mode+0x5d/0x160 kernel/entry/common.c:218 > do_syscall_64+0xe4/0x1f0 arch/x86/entry/common.c:89 > entry_SYSCALL_64_after_hwframe+0x72/0x7a > > CPU: 0 PID: 5014 Comm: segctord Not tainted 6.9.0-rc2-syzkaller-00207-ge8b0ccb2a787 #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024 > ===================================================== > > > --- > 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. #syz fix: x86: call instrumentation hooks from copy_mc.c This is one of the false positive warnings that the memory dumped by elf_core_dump() was mixed into the file system side via copy_mc_to_kernel() of x86, which was called with the following call path and did not support KMSAN until recently: elf_core_dump dump_user_range dump_page_copy copy_mc_to_kernel dump_emit_page ... Given the syzbot CPU information, we can confirm that the x86 ERMS feature flag is set, a condition that is affected by the issue. The above commit, which was merged during the merge window for v6.10, made copy_mc_to_kernel() on x86 KMSAN-compatible and should have fixed this issue. Ryusuke Konishi
