[EXT4 FS bs=1024, gc=1, bpg=131072, ipg=32, mo=e84ce028, mo2=0000]
==================================================================
BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff86cbc918 of 88 bytes by task 1897 on cpu 1:
 prb_reserve+0x6fb/0xaf0 kernel/printk/printk_ringbuffer.c:1693
 vprintk_store+0x54a/0x910 kernel/printk/printk.c:2354
 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2455
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2494
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2504
 __netdev_printk+0x310/0x370 net/core/dev.c:12972
 netdev_info+0xa6/0xd0 net/core/dev.c:13019
 __dev_set_promiscuity+0x1e5/0x3c0 net/core/dev.c:9620
 __dev_change_flags+0x266/0x490 net/core/dev.c:9769
 netif_change_flags+0x53/0xc0 net/core/dev.c:9823
 dev_change_flags+0xbc/0x180 net/core/dev_api.c:68
 dev_ifsioc+0x439/0xfc0 net/core/dev_ioctl.c:555
 dev_ioctl+0x709/0x960 net/core/dev_ioctl.c:816
 sock_do_ioctl+0x1aa/0x230 net/socket.c:1314
 sock_ioctl+0x439/0x610 net/socket.c:1421
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xce/0x140 fs/ioctl.c:583
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:583
 x64_sys_call+0x1563/0x3020 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86cbc918 of 8 bytes by task 1891 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:500 [inline]
 prb_first_seq kernel/printk/printk_ringbuffer.c:2017 [inline]
 _prb_read_valid+0x325/0x930 kernel/printk/printk_ringbuffer.c:2174
 desc_update_last_finalized+0x8f/0x170 kernel/printk/printk_ringbuffer.c:1573
 prb_final_commit+0x111/0x150 kernel/printk/printk_ringbuffer.c:1842
 vprintk_store+0x88b/0x910 kernel/printk/printk.c:2381
 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2455
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2494
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2504
 ext4_setup_super+0x572/0x580 fs/ext4/super.c:3155
 __ext4_fill_super fs/ext4/super.c:5622 [inline]
 ext4_fill_super+0x29ab/0x3760 fs/ext4/super.c:5828
 get_tree_bdev_flags+0x291/0x300 fs/super.c:1634
 get_tree_bdev+0x1f/0x30 fs/super.c:1657
 ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5860
 vfs_get_tree+0x57/0x1d0 fs/super.c:1694
 fc_mount fs/namespace.c:1198 [inline]
 do_new_mount_fc fs/namespace.c:3765 [inline]
 do_new_mount+0x288/0x8d0 fs/namespace.c:3841
 path_mount+0x4ad/0xb90 fs/namespace.c:4161
 do_mount fs/namespace.c:4174 [inline]
 __do_sys_mount fs/namespace.c:4390 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4367
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4367
 x64_sys_call+0x2d61/0x3020 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000002753 -> 0x0000000000004753

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 1891 Comm: syz.6.9151 Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
==================================================================
System zones: 0-1, 3-12
EXT4-fs error (device loop6): ext4_map_blocks:833: inode #3: block 1: comm syz.6.9151: lblock 1 mapped to illegal pblock 1 (length 1)
loop6: lost file I/O error report for ino 3 type 5 pos 0x0 len 0x0 error -117
EXT4-fs (loop6): Remounting filesystem read-only
EXT4-fs (loop6): 1 orphan inode deleted
EXT4-fs (loop6): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: writeback.
netlink: 28 bytes leftover after parsing attributes in process `syz.6.9151'.