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[129.132.161.179]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4601f3444fesm19638353f8f.20.2026.06.04.10.10.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Jun 2026 10:10:46 -0700 (PDT) From: Zijing Yin To: Thomas Gleixner , Anna-Maria Behnsen , Frederic Weisbecker Cc: Zijing Yin , linux-kernel@vger.kernel.org Subject: UBSAN: invalid-load in __remove_hrtimer Date: Thu, 4 Jun 2026 10:10:41 -0700 Message-ID: <20260604171043.995130-1-yzjaurora@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi, Fuzzing v7.1-rc1 (98878ed91b68) with a customized syzkaller on a KASAN+UBSAN build, I hit the UBSAN invalid-load below in __remove_hrtimer() (a bool field read as 255). On the same run it is immediately followed by a general protection fault on a non-canonical pointer while __remove_hrtimer() walks the timer rbtree. The syzkaller reproducer (repro.prog), a C reproducer (repro.cprog), and the kernel .config (repro.config) are attached. It reproduces when the reproducer is replayed on a KASAN+UBSAN kernel, though not on every run (roughly 1 VM in 4 within a few minutes); still reachable on the current mainline tip. I can send the full dmesg, the disk image, or test a debugging patch on request. syzkaller repro: https://bugzilla.kernel.org/attachment.cgi?id=310263 C repro: https://bugzilla.kernel.org/attachment.cgi?id=310264 .config: https://bugzilla.kernel.org/attachment.cgi?id=310265 Full splat: ------------[ cut here ]------------ UBSAN: invalid-load in kernel/time/hrtimer.c:1147:14 load of value 255 is not a valid value for type 'bool' (aka '_Bool') CPU: 0 UID: 0 PID: 1479 Comm: syz.5.22 Tainted: G B 7.1.0-rc1-g98878ed91b68-dirty #3 PREEMPT(lazy) Tainted: [B]=BAD_PAGE Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Call Trace: __dump_stack+0x21/0x30 lib/dump_stack.c:94 dump_stack_lvl+0x5f/0x8c lib/dump_stack.c:120 dump_stack+0x19/0x20 lib/dump_stack.c:129 ubsan_epilogue+0xe/0x40 lib/ubsan.c:233 __ubsan_handle_load_invalid_value+0xf2/0x100 lib/ubsan.c:527 __remove_hrtimer+0x436/0x520 kernel/time/hrtimer.c:1147 __hrtimer_run_queues+0x282/0x900 kernel/time/hrtimer.c:1910 hrtimer_run_queues+0x1a4/0x210 kernel/time/hrtimer.c:2177 update_process_times+0x34/0x2b0 kernel/time/timer.c:2420 tick_nohz_handler+0x468/0x7d0 kernel/time/tick-sched.c:298 tick_nohz_lowres_handler+0x68/0xd0 kernel/time/tick-sched.c:1531 __sysvec_apic_timer_interrupt+0x5e/0x270 arch/x86/kernel/apic/apic.c:1050 sysvec_apic_timer_interrupt+0x72/0x90 arch/x86/kernel/apic/apic.c:1061 asm_sysvec_apic_timer_interrupt+0x1f/0x30 arch/x86/include/asm/idtentry.h:697 RIP: 0010:memmove+0x1e/0x1b0 arch/x86/lib/memmove_64.S:45 Code: 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 89 f8 48 39 fe 7d 0f 49 89 f0 49 01 d0 49 39 f8 0f 8f b5 00 00 00 48 89 d1 a4 e9 96 ac d3 f8 66 2e 0f 1f 84 00 00 00 00 00 48 81 fa a8 02 RSP: 0018:ff110001273ce6c8 EFLAGS: 00000206 RAX: ff1100011372dea4 RBX: fffffffffffffff0 RCX: fffffffffd9786db RDX: fffffffffffffff0 RSI: ff11000115db57cd RDI: ff11000115db57b9 RBP: ff110001273ce6f8 R08: ff1100011372de94 R09: 0000000000000000 R10: 00000000ffffffc3 R11: 0000000000000000 R12: 0000000000000000 R13: ffffffff82759003 R14: ff1100011372deb8 R15: ff1100011372dea4 ext4_xattr_set_entry+0xc13/0x2390 fs/ext4/xattr.c:1763 ext4_xattr_ibody_set+0x29e/0x740 fs/ext4/xattr.c:2275 ext4_destroy_inline_data_nolock+0x24b/0x630 fs/ext4/inline.c:472 ext4_destroy_inline_data+0x87/0x100 fs/ext4/inline.c:1806 ext4_do_writepages+0x5c7/0x4e40 fs/ext4/inode.c:2827 ext4_writepages+0x213/0x390 fs/ext4/inode.c:3042 do_writepages+0x389/0x5c0 mm/page-writeback.c:2575 file_write_and_wait_range+0x2f6/0x390 mm/filemap.c:388 mmb_fsync_noflush+0x87/0x240 fs/buffer.c:645 ext4_sync_file+0x3aa/0xba0 fs/ext4/fsync.c:92 vfs_fsync_range+0x168/0x190 fs/sync.c:186 ext4_buffered_write_iter+0x752/0x8a0 include/linux/fs.h:2654 ext4_file_write_iter+0x707/0x1bf0 iter_file_splice_write+0xa08/0x1230 fs/splice.c:736 direct_splice_actor+0x123/0x180 fs/splice.c:936 splice_direct_to_actor+0x548/0xcf0 fs/splice.c:1103 do_splice_direct+0x192/0x290 fs/splice.c:1202 do_sendfile+0x5cf/0xae0 fs/read_write.c:1372 __se_sys_sendfile64+0x145/0x1b0 fs/read_write.c:1433 __x64_sys_sendfile64+0x9f/0xb0 fs/read_write.c:1419 x64_sys_call+0x2dce/0x3030 arch/x86/include/generated/asm/syscalls_64.h:41 do_syscall_64+0xf7/0x3e0 arch/x86/entry/syscall_64.c:63 entry_SYSCALL_64_after_hwframe+0x74/0x7c RIP: 0033:0x7f56a8a20a3d RSP: 002b:00007f56a8046048 EFLAGS: 00000212 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 00007f56a8ac4ece RCX: 00007f56a8a20a3d RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000007 RBP: 00007f56a8046080 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000100000000 R11: 0000000000000212 R12: 00007f56a80466c0 R13: ffffffffffffffb0 R14: 000000000000000b R15: 00007fff53f1de10 ---[ end trace ]--- Oops: general protection fault, probably for non-canonical address 0xf1a7c288031699ea: 0000 [#1] KASAN NOPTI KASAN: maybe wild-memory-access in range [0x8d3e344018b4cf50-0x8d3e344018b4cf57] CPU: 0 UID: 0 PID: 1479 Comm: syz.5.22 Tainted: G B 7.1.0-rc1-g98878ed91b68-dirty #3 PREEMPT(lazy) Tainted: [B]=BAD_PAGE RIP: 0010:rb_erase_linked+0x89/0x1a0 lib/rbtree.c:452 Call Trace: timerqueue_linked_del include/linux/timerqueue.h:66 [inline] __remove_hrtimer+0x162/0x520 kernel/time/hrtimer.c:1155 __hrtimer_run_queues+0x282/0x900 kernel/time/hrtimer.c:1910 hrtimer_run_queues+0x1a4/0x210 kernel/time/hrtimer.c:2177 update_process_times+0x34/0x2b0 kernel/time/timer.c:2420 tick_nohz_handler+0x468/0x7d0 kernel/time/tick-sched.c:298 tick_nohz_lowres_handler+0x68/0xd0 kernel/time/tick-sched.c:1531 __sysvec_apic_timer_interrupt+0x5e/0x270 arch/x86/kernel/apic/apic.c:1050 sysvec_apic_timer_interrupt+0x72/0x90 arch/x86/kernel/apic/apic.c:1061 ---[ end trace 0000000000000000 ]--- Thanks, Zijing Yin