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BUG: KCSAN: data-race in iov_iter_copy_from_user_atomic / memcmp

write to 0xffff8880965a3000 of 4096 bytes by task 24107 on cpu 1:
 instrument_copy_from_user include/linux/instrumented.h:136 [inline]
 copyin lib/iov_iter.c:156 [inline]
 iov_iter_copy_from_user_atomic+0x33b/0x830 lib/iov_iter.c:991
 generic_perform_write+0x1e4/0x3a0 mm/filemap.c:3583
 ext4_buffered_write_iter+0x2e5/0x3e0 fs/ext4/file.c:269
 ext4_file_write_iter+0x48a/0x10b0 fs/ext4/file.c:502
 call_write_iter include/linux/fs.h:1977 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x6f9/0x7e0 fs/read_write.c:605
 ksys_write+0xce/0x180 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:667
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff8880965a34b2 of 1 bytes by task 24114 on cpu 0:
 memcmp+0x33/0x60 lib/string.c:939
 memcmp_pages+0x99/0x140
 pages_identical include/linux/mm.h:3154 [inline]
 uprobe_write_opcode+0x6ab/0xd60 kernel/events/uprobes.c:533
 set_orig_insn+0x2c/0x40
 remove_breakpoint kernel/events/uprobes.c:926 [inline]
 register_for_each_vma+0x7ae/0x890 kernel/events/uprobes.c:1073
 uprobe_apply+0x8b/0x260 kernel/events/uprobes.c:1229
 uprobe_perf_close+0x2e8/0x350 kernel/trace/trace_uprobe.c:1292
 trace_uprobe_register+0x13f/0x410 kernel/trace/trace_uprobe.c:1471
 perf_trace_event_close kernel/trace/trace_event_perf.c:192 [inline]
 perf_uprobe_destroy+0x58/0x90 kernel/trace/trace_event_perf.c:348
 _free_event+0x867/0xbb0 kernel/events/core.c:4863
 free_event kernel/events/core.c:4898 [inline]
 __do_sys_perf_event_open kernel/events/core.c:12213 [inline]
 __se_sys_perf_event_open+0x1d90/0x25d0 kernel/events/core.c:11775
 __x64_sys_perf_event_open+0x63/0x70 kernel/events/core.c:11775
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 24114 Comm: syz-executor.0 Tainted: G        W         5.12.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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