On Fri, 21 Apr 2023 at 16:36, syzbot <syzbot+726dc8c62c3536431ceb@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > Hello, > > syzbot found the following issue on: > > HEAD commit: 2faac9a98f01 Merge tag 'keys-fixes-20230321' of git://git... > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=1113f21cc80000 > kernel config: https://syzkaller.appspot.com/x/.config?x=3eb0bb0ae89a5345 > dashboard link: https://syzkaller.appspot.com/bug?extid=726dc8c62c3536431ceb > 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/571c9c5a3db2/disk-2faac9a9.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/a051e3d7c495/vmlinux-2faac9a9.xz > kernel image: https://storage.googleapis.com/syzbot-assets/ff5ec0d6e37d/bzImage-2faac9a9.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+726dc8c62c3536431ceb@xxxxxxxxxxxxxxxxxxxxxxxxx Here this: size = min_t(unsigned int, size, vi->data_avail); memcpy(buf, vi->data + vi->data_idx, size); vi->data_idx += size; vi->data_avail -= size; runs concurrently with: if (!virtqueue_get_buf(vi->vq, &vi->data_avail)) return; vi->data_idx = 0; I did not fully grasp how/where vi->data is populated, but it looks like it can lead to use of uninit/stale random data, or even to out of bounds access, say if vi->data_avail is already updated, but vi->data_idx is not yet reset to 0. Then concurrent reading will read not where it's supposed to read. > ================================================================== > BUG: KCSAN: data-race in random_recv_done / virtio_read > > read to 0xffff8881019054ec of 4 bytes by task 14079 on cpu 0: > copy_data drivers/char/hw_random/virtio-rng.c:70 [inline] > virtio_read+0xc3/0x3f0 drivers/char/hw_random/virtio-rng.c:92 > rng_get_data drivers/char/hw_random/core.c:197 [inline] > rng_dev_read+0x1a7/0x5e0 drivers/char/hw_random/core.c:234 > vfs_read+0x192/0x560 fs/read_write.c:468 > ksys_read+0xeb/0x1a0 fs/read_write.c:613 > __do_sys_read fs/read_write.c:623 [inline] > __se_sys_read fs/read_write.c:621 [inline] > __x64_sys_read+0x42/0x50 fs/read_write.c:621 > 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 > > write to 0xffff8881019054ec of 4 bytes by interrupt on cpu 1: > random_recv_done+0x62/0x90 drivers/char/hw_random/virtio-rng.c:45 > vring_interrupt+0x150/0x170 drivers/virtio/virtio_ring.c:2491 > __handle_irq_event_percpu+0x91/0x490 kernel/irq/handle.c:158 > handle_irq_event_percpu kernel/irq/handle.c:193 [inline] > handle_irq_event+0x64/0xf0 kernel/irq/handle.c:210 > handle_edge_irq+0x17f/0x5a0 kernel/irq/chip.c:819 > generic_handle_irq_desc include/linux/irqdesc.h:158 [inline] > handle_irq arch/x86/kernel/irq.c:231 [inline] > __common_interrupt+0x64/0x100 arch/x86/kernel/irq.c:250 > common_interrupt+0x49/0xc0 arch/x86/kernel/irq.c:240 > asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:636 > > value changed: 0x00000000 -> 0x00000040 > > Reported by Kernel Concurrency Sanitizer on: > CPU: 1 PID: 14077 Comm: syz-executor.2 Not tainted 6.3.0-rc3-syzkaller-00016-g2faac9a98f01 #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023 > ================================================================== > ================================================================== > BUG: KCSAN: data-race in detach_buf_split / virtqueue_add > > read to 0xffff888101a76950 of 4 bytes by task 14131 on cpu 0: > virtqueue_add_split drivers/virtio/virtio_ring.c:553 [inline] > virtqueue_add+0x4b9/0x2130 drivers/virtio/virtio_ring.c:2117 > virtqueue_add_inbuf+0x53/0x80 drivers/virtio/virtio_ring.c:2196 > request_entropy drivers/char/hw_random/virtio-rng.c:61 [inline] > copy_data drivers/char/hw_random/virtio-rng.c:74 [inline] > virtio_read+0x1c5/0x3f0 drivers/char/hw_random/virtio-rng.c:92 > rng_get_data drivers/char/hw_random/core.c:197 [inline] > rng_dev_read+0x1a7/0x5e0 drivers/char/hw_random/core.c:234 > vfs_read+0x192/0x560 fs/read_write.c:468 > ksys_read+0xeb/0x1a0 fs/read_write.c:613 > __do_sys_read fs/read_write.c:623 [inline] > __se_sys_read fs/read_write.c:621 [inline] > __x64_sys_read+0x42/0x50 fs/read_write.c:621 > 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-write to 0xffff888101a76950 of 4 bytes by interrupt on cpu 1: > detach_buf_split+0x2fc/0x570 drivers/virtio/virtio_ring.c:757 > virtqueue_get_buf_ctx_split drivers/virtio/virtio_ring.c:835 [inline] > virtqueue_get_buf_ctx+0x3c8/0x5c0 drivers/virtio/virtio_ring.c:2311 > virtqueue_get_buf+0x1f/0x30 drivers/virtio/virtio_ring.c:2317 > random_recv_done+0x4c/0x90 drivers/char/hw_random/virtio-rng.c:42 > vring_interrupt+0x150/0x170 drivers/virtio/virtio_ring.c:2491 > __handle_irq_event_percpu+0x91/0x490 kernel/irq/handle.c:158 > handle_irq_event_percpu kernel/irq/handle.c:193 [inline] > handle_irq_event+0x64/0xf0 kernel/irq/handle.c:210 > handle_edge_irq+0x17f/0x5a0 kernel/irq/chip.c:819 > generic_handle_irq_desc include/linux/irqdesc.h:158 [inline] > handle_irq arch/x86/kernel/irq.c:231 [inline] > __common_interrupt+0x64/0x100 arch/x86/kernel/irq.c:250 > common_interrupt+0x9e/0xc0 arch/x86/kernel/irq.c:240 > asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:636 > xas_find+0x10a/0x3f0 > find_get_entry mm/filemap.c:2008 [inline] > filemap_get_folios+0xa4/0x3f0 mm/filemap.c:2174 > mpage_map_and_submit_buffers fs/ext4/inode.c:2358 [inline] > mpage_map_and_submit_extent fs/ext4/inode.c:2513 [inline] > ext4_do_writepages+0x1017/0x2140 fs/ext4/inode.c:2876 > ext4_writepages+0x127/0x250 fs/ext4/inode.c:2964 > do_writepages+0x1c5/0x340 mm/page-writeback.c:2551 > filemap_fdatawrite_wbc+0xdb/0xf0 mm/filemap.c:390 > __filemap_fdatawrite_range mm/filemap.c:423 [inline] > __filemap_fdatawrite mm/filemap.c:429 [inline] > filemap_flush+0x95/0xc0 mm/filemap.c:456 > ext4_alloc_da_blocks+0x50/0x130 fs/ext4/inode.c:3218 > ext4_release_file+0x5f/0x1c0 fs/ext4/file.c:158 > __fput+0x245/0x570 fs/file_table.c:321 > ____fput+0x15/0x20 fs/file_table.c:349 > task_work_run+0x123/0x160 kernel/task_work.c:179 > exit_task_work include/linux/task_work.h:38 [inline] > do_exit+0x600/0x1710 kernel/exit.c:869 > do_group_exit+0x101/0x150 kernel/exit.c:1019 > get_signal+0xea9/0xfe0 kernel/signal.c:2859 > arch_do_signal_or_restart+0x89/0x2b0 arch/x86/kernel/signal.c:306 > exit_to_user_mode_loop+0x6d/0xe0 kernel/entry/common.c:168 > exit_to_user_mode_prepare+0x6a/0xa0 kernel/entry/common.c:203 > irqentry_exit_to_user_mode+0x9/0x20 kernel/entry/common.c:309 > irqentry_exit+0x12/0x40 kernel/entry/common.c:412 > exc_general_protection+0x339/0x4c0 arch/x86/kernel/traps.c:728 > asm_exc_general_protection+0x26/0x30 arch/x86/include/asm/idtentry.h:564 > > value changed: 0x00000001 -> 0x00000000 > > Reported by Kernel Concurrency Sanitizer on: > CPU: 1 PID: 14098 Comm: syz-executor.1 Not tainted 6.3.0-rc3-syzkaller-00016-g2faac9a98f01 #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023 > ================================================================== > > > --- > 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.
