syzbot

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BUG: KCSAN: data-race in ktime_get_coarse_real_ts64 / timekeeping_update_from_shadow

write to 0xffffffff893ae488 of 304 bytes by interrupt on cpu 0:
 timekeeping_update_from_shadow+0x40d/0x440 kernel/time/timekeeping.c:829
 __timekeeping_advance+0xa5d/0xc10 kernel/time/timekeeping.c:2532
 timekeeping_advance kernel/time/timekeeping.c:2540 [inline]
 update_wall_time+0x21/0x50 kernel/time/timekeeping.c:2550
 tick_do_update_jiffies64+0x169/0x1c0 kernel/time/tick-sched.c:149
 tick_sched_do_timer kernel/time/tick-sched.c:253 [inline]
 tick_nohz_handler+0x8d/0x3d0 kernel/time/tick-sched.c:312
 __run_hrtimer kernel/time/hrtimer.c:1930 [inline]
 __hrtimer_run_queues+0x276/0x4f0 kernel/time/hrtimer.c:1994
 hrtimer_interrupt+0x261/0x850 kernel/time/hrtimer.c:2113
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
 __sysvec_apic_timer_interrupt+0x5f/0x1c0 arch/x86/kernel/apic/apic.c:1067
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1061 [inline]
 sysvec_apic_timer_interrupt+0x6f/0x80 arch/x86/kernel/apic/apic.c:1061
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
 kcsan_setup_watchpoint+0x404/0x410 kernel/kcsan/core.c:705
 lowmem_page_address include/linux/mm.h:2973 [inline]
 folio_address include/linux/mm.h:2984 [inline]
 slab_address mm/slab.h:153 [inline]
 obj_to_index mm/slab.h:305 [inline]
 __memcg_slab_free_hook+0x99/0x2c0 mm/memcontrol.c:3528
 memcg_slab_free_hook mm/slub.c:2488 [inline]
 slab_free mm/slub.c:6248 [inline]
 kfree+0x291/0x370 mm/slub.c:6566
 skb_kfree_head net/core/skbuff.c:1075 [inline]
 skb_free_head+0x53/0x220 net/core/skbuff.c:1087
 skb_release_data+0x5c4/0x600 net/core/skbuff.c:1114
 skb_release_all net/core/skbuff.c:1189 [inline]
 __kfree_skb+0x44/0x150 net/core/skbuff.c:1203
 consume_skb+0x4b/0x130 net/core/skbuff.c:1436
 skb_free_datagram+0x15/0x20 net/core/datagram.c:324
 __unix_dgram_recvmsg+0x784/0x870 net/unix/af_unix.c:2669
 unix_dgram_recvmsg+0x7e/0x90 net/unix/af_unix.c:2686
 sock_recvmsg_nosec net/socket.c:1137 [inline]
 sock_recvmsg+0xf5/0x120 net/socket.c:1159
 sock_read_iter+0x169/0x1b0 net/socket.c:1229
 new_sync_read fs/read_write.c:493 [inline]
 vfs_read+0x6c0/0x7f0 fs/read_write.c:574
 ksys_read+0xdc/0x1a0 fs/read_write.c:717
 __do_sys_read fs/read_write.c:726 [inline]
 __se_sys_read fs/read_write.c:724 [inline]
 __x64_sys_read+0x40/0x50 fs/read_write.c:724
 x64_sys_call+0x2886/0x3020 arch/x86/include/generated/asm/syscalls_64.h:1
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff893ae4f8 of 4 bytes by task 3023 on cpu 1:
 tk_xtime_coarse kernel/time/timekeeping.c:212 [inline]
 ktime_get_coarse_real_ts64+0x6b/0xf0 kernel/time/timekeeping.c:2583
 audit_get_stamp kernel/audit.c:1892 [inline]
 audit_log_start+0x5b7/0x730 kernel/audit.c:1970
 common_lsm_audit+0x65/0x230 security/lsm_audit.c:442
 slow_avc_audit+0x14c/0x190 security/selinux/avc.c:779
 avc_audit security/selinux/include/avc.h:131 [inline]
 avc_has_perm+0x144/0x190 security/selinux/avc.c:1198
 sock_has_perm security/selinux/hooks.c:4928 [inline]
 selinux_socket_recvmsg+0x1ab/0x1e0 security/selinux/hooks.c:5275
 security_socket_recvmsg+0x4c/0x90 security/security.c:4330
 sock_recvmsg+0x38/0x120 net/socket.c:1157
 ____sys_recvmsg+0xf5/0x280 net/socket.c:2918
 ___sys_recvmsg+0x11f/0x3b0 net/socket.c:2960
 __sys_recvmsg net/socket.c:2993 [inline]
 __do_sys_recvmsg net/socket.c:2999 [inline]
 __se_sys_recvmsg net/socket.c:2996 [inline]
 __x64_sys_recvmsg+0xd1/0x160 net/socket.c:2996
 x64_sys_call+0x2b1a/0x3020 arch/x86/include/generated/asm/syscalls_64.h:48
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x1c09ccd9 -> 0x1c9887ea

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3023 Comm: dhcpcd Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
==================================================================
audit: audit_backlog=65 > audit_backlog_limit=64
audit: audit_lost=1327 audit_rate_limit=0 audit_backlog_limit=64
audit: backlog limit exceeded
audit: audit_backlog=65 > audit_backlog_limit=64
audit: audit_lost=1328 audit_rate_limit=0 audit_backlog_limit=64
audit: audit_backlog=65 > audit_backlog_limit=64
audit: audit_lost=1537 audit_rate_limit=0 audit_backlog_limit=64
audit: backlog limit exceeded
audit: audit_backlog=65 > audit_backlog_limit=64
audit: audit_lost=1538 audit_rate_limit=0 audit_backlog_limit=64