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BUG: KCSAN: data-race in _prb_read_valid / data_alloc

write to 0xffffffff86c78d08 of 8 bytes by task 32419 on cpu 1:
 data_alloc+0x310/0x390 kernel/printk/printk_ringbuffer.c:1129
 prb_reserve+0x8d7/0xae0 kernel/printk/printk_ringbuffer.c:1724
 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
 batadv_tt_local_add+0x14ba/0x1720 net/batman-adv/translation-table.c:666
 batadv_interface_tx+0x42b/0xae0 net/batman-adv/mesh-interface.c:236
 __netdev_start_xmit include/linux/netdevice.h:5325 [inline]
 netdev_start_xmit include/linux/netdevice.h:5334 [inline]
 xmit_one net/core/dev.c:3888 [inline]
 dev_hard_start_xmit+0x136/0x3f0 net/core/dev.c:3904
 __dev_queue_xmit+0xd9a/0x1f20 net/core/dev.c:4854
 dev_queue_xmit include/linux/netdevice.h:3385 [inline]
 __bpf_tx_skb net/core/filter.c:2152 [inline]
 __bpf_redirect_common net/core/filter.c:2196 [inline]
 __bpf_redirect+0x862/0x990 net/core/filter.c:2203
 ____bpf_clone_redirect net/core/filter.c:2493 [inline]
 bpf_clone_redirect+0x20c/0x290 net/core/filter.c:2456
 bpf_prog_ba7156dd260b21a3+0x62/0x6b
 bpf_dispatcher_nop_func include/linux/bpf.h:1402 [inline]
 __bpf_prog_run include/linux/filter.h:723 [inline]
 bpf_prog_run include/linux/filter.h:730 [inline]
 bpf_test_run+0x29d/0x620 net/bpf/test_run.c:423
 bpf_prog_test_run_skb+0x9a4/0xef0 net/bpf/test_run.c:1159
 bpf_prog_test_run+0x204/0x340 kernel/bpf/syscall.c:4743
 __sys_bpf+0x52e/0x7e0 kernel/bpf/syscall.c:6267
 __do_sys_bpf kernel/bpf/syscall.c:6362 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:6360 [inline]
 __x64_sys_bpf+0x41/0x50 kernel/bpf/syscall.c:6360
 x64_sys_call+0x10cb/0x3020 arch/x86/include/generated/asm/syscalls_64.h:322
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86c78d08 of 16 bytes by task 2988 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:496 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1931 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1979 [inline]
 _prb_read_valid+0x1bc/0x950 kernel/printk/printk_ringbuffer.c:2170
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2242
 syslog_print+0x258/0x560 kernel/printk/printk.c:1628
 do_syslog+0x52b/0x7f0 kernel/printk/printk.c:1763
 __do_sys_syslog kernel/printk/printk.c:1855 [inline]
 __se_sys_syslog kernel/printk/printk.c:1853 [inline]
 __x64_sys_syslog+0x41/0x50 kernel/printk/printk.c:1853
 x64_sys_call+0x2b9e/0x3020 arch/x86/include/generated/asm/syscalls_64.h:104
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 2988 Comm: klogd Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
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