On Tue, Apr 16, 2024 at 06:14:20AM -0700, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: cef27048e5c2 Merge tag 'bcachefs-2024-04-15' of https://ev.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=11a1fec7180000 > kernel config: https://syzkaller.appspot.com/x/.config?x=87a805e655619c64 > dashboard link: https://syzkaller.appspot.com/bug?extid=510a1abbb8116eeb341d > 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/fce0439cf562/disk-cef27048.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/99540e71cf72/vmlinux-cef27048.xz > kernel image: https://storage.googleapis.com/syzbot-assets/65fbfc2c486f/bzImage-cef27048.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+510a1abbb8116eeb341d@xxxxxxxxxxxxxxxxxxxxxxxxx > > BTRFS info (device loop1): first mount of filesystem c9fe44da-de57-406a-8241-57ec7d4412cf > BTRFS info (device loop1): using crc32c (crc32c-generic) checksum algorithm > BTRFS info (device loop1): using free-space-tree > ===================================================== > BUG: KMSAN: kernel-infoleak in instrument_copy_to_user include/linux/instrumented.h:114 [inline] > BUG: KMSAN: kernel-infoleak in _copy_to_user+0xbc/0x110 lib/usercopy.c:40 > instrument_copy_to_user include/linux/instrumented.h:114 [inline] > _copy_to_user+0xbc/0x110 lib/usercopy.c:40 > copy_to_user include/linux/uaccess.h:191 [inline] > btrfs_ioctl_logical_to_ino+0x440/0x750 fs/btrfs/ioctl.c:3499 > btrfs_ioctl+0x714/0x1260 > vfs_ioctl fs/ioctl.c:51 [inline] > __do_sys_ioctl fs/ioctl.c:904 [inline] > __se_sys_ioctl+0x261/0x450 fs/ioctl.c:890 > __x64_sys_ioctl+0x96/0xe0 fs/ioctl.c:890 > x64_sys_call+0x1883/0x3b50 arch/x86/include/generated/asm/syscalls_64.h:17 > 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 > > Uninit was created at: > __kmalloc_large_node+0x231/0x370 mm/slub.c:3921 > __do_kmalloc_node mm/slub.c:3954 [inline] > __kmalloc_node+0xb07/0x1060 mm/slub.c:3973 > kmalloc_node include/linux/slab.h:648 [inline] > kvmalloc_node+0xc0/0x2d0 mm/util.c:634 > kvmalloc include/linux/slab.h:766 [inline] > init_data_container+0x49/0x1e0 fs/btrfs/backref.c:2779 2767 struct btrfs_data_container *init_data_container(u32 total_bytes) 2768 { 2769 struct btrfs_data_container *data; 2770 size_t alloc_bytes; 2771 2772 alloc_bytes = max_t(size_t, total_bytes, sizeof(*data)); 2773 data = kvmalloc(alloc_bytes, GFP_KERNEL); and then data is passed around in the ioctl. > btrfs_ioctl_logical_to_ino+0x17c/0x750 fs/btrfs/ioctl.c:3480 > btrfs_ioctl+0x714/0x1260 > vfs_ioctl fs/ioctl.c:51 [inline] > __do_sys_ioctl fs/ioctl.c:904 [inline] > __se_sys_ioctl+0x261/0x450 fs/ioctl.c:890 > __x64_sys_ioctl+0x96/0xe0 fs/ioctl.c:890 > x64_sys_call+0x1883/0x3b50 arch/x86/include/generated/asm/syscalls_64.h:17 > 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 > > Bytes 40-65535 of 65536 are uninitialized It is possible to let the ioctl allocate a big buffer but return it filled only partially. So it should be kvcalloc.
