syzbot

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BUG: KCSAN: data-race in random_recv_done / virtio_read

read to 0xffff88810123e0cc of 4 bytes by task 15589 on cpu 0:
 copy_data drivers/char/hw_random/virtio-rng.c:70 [inline]
 virtio_read+0xc2/0x450 drivers/char/hw_random/virtio-rng.c:92
 rng_get_data drivers/char/hw_random/core.c:192 [inline]
 rng_dev_read+0x1b4/0x630 drivers/char/hw_random/core.c:229
 do_loop_readv_writev fs/read_write.c:746 [inline]
 do_iter_read+0x370/0x5d0 fs/read_write.c:788
 vfs_readv fs/read_write.c:906 [inline]
 do_preadv+0x159/0x240 fs/read_write.c:998
 __do_sys_preadv fs/read_write.c:1048 [inline]
 __se_sys_preadv fs/read_write.c:1043 [inline]
 __x64_sys_preadv+0x54/0x60 fs/read_write.c:1043
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

write to 0xffff88810123e0cc of 4 bytes by interrupt on cpu 1:
 random_recv_done+0x58/0x80 drivers/char/hw_random/virtio-rng.c:45
 vring_interrupt+0x15d/0x180 drivers/virtio/virtio_ring.c:2165
 __handle_irq_event_percpu+0x92/0x450 kernel/irq/handle.c:158
 handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
 handle_irq_event+0x7b/0x110 kernel/irq/handle.c:210
 handle_edge_irq+0x18e/0x5f0 kernel/irq/chip.c:820
 generic_handle_irq_desc include/linux/irqdesc.h:158 [inline]
 handle_irq arch/x86/kernel/irq.c:231 [inline]
 __common_interrupt+0x60/0x100 arch/x86/kernel/irq.c:250
 common_interrupt+0x9a/0xc0 arch/x86/kernel/irq.c:240
 asm_common_interrupt+0x1e/0x40
 __tsan_read8+0xe/0x180 kernel/kcsan/core.c:1014
 avc_has_perm_noaudit+0x6b/0x270 security/selinux/avc.c:1152
 selinux_inode_permission+0x2da/0x3f0 security/selinux/hooks.c:3155
 security_inode_permission+0x72/0xc0 security/security.c:1317
 inode_permission fs/namei.c:532 [inline]
 may_lookup fs/namei.c:1733 [inline]
 link_path_walk+0x1e2/0x990 fs/namei.c:2289
 path_lookupat+0x8b/0x3d0 fs/namei.c:2498
 filename_lookup+0x130/0x310 fs/namei.c:2528
 user_path_at_empty+0x3e/0x110 fs/namei.c:2851
 do_readlinkat+0x97/0x210 fs/stat.c:443
 __do_sys_readlink fs/stat.c:476 [inline]
 __se_sys_readlink fs/stat.c:473 [inline]
 __x64_sys_readlink+0x43/0x50 fs/stat.c:473
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000000 -> 0x00000040

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 1440 Comm: udevd Not tainted 5.17.0-rc4-syzkaller-00217-g7993e65fdd0f-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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virtio_rng virtio3: input:id 0 is not a head!