Re: [syzbot] [kernel?] KMSAN: uninit-value in irqentry_exit_to_kernel_mode_preempt

[syzbot <syzbot+23d7fcd204e3837866ff@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    66edb901bf87 Merge tag 'v7.1-p3' of git://git.kernel.org/p..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=107b2dba580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1c3f61154f3bb7e5
dashboard link: https://syzkaller.appspot.com/bug?extid=23d7fcd204e3837866ff
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=126caece580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11f00d06580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9014c04fc561/disk-66edb901.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a96b1e11a924/vmlinux-66edb901.xz
kernel image: https://storage.googleapis.com/syzbot-assets/680236de6331/bzImage-66edb901.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+23d7fcd204e3837866ff@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in irqentry_exit_to_kernel_mode_preempt+0xb0/0xc0 include/linux/irq-entry-common.h:472
 irqentry_exit_to_kernel_mode_preempt+0xb0/0xc0 include/linux/irq-entry-common.h:472
 irqentry_exit_to_kernel_mode include/linux/irq-entry-common.h:547 [inline]
 irqentry_exit+0x7b/0x760 kernel/entry/common.c:164
 sysvec_apic_timer_interrupt+0x52/0x90 arch/x86/kernel/apic/apic.c:1061
 asm_sysvec_apic_timer_interrupt+0x1f/0x30 arch/x86/include/asm/idtentry.h:697
 encrypted_key_alloc+0x8c9/0xa70 security/keys/encrypted-keys/encrypted.c:641
 encrypted_instantiate+0x45e/0x3220 security/keys/encrypted-keys/encrypted.c:812
 __key_instantiate_and_link+0xfe/0x5d0 security/keys/key.c:446
 __key_create_or_update+0x12c4/0x1500 security/keys/key.c:941
 key_create_or_update+0x5f/0x80 security/keys/key.c:1021
 __do_sys_add_key security/keys/keyctl.c:134 [inline]
 __se_sys_add_key+0x656/0x870 security/keys/keyctl.c:74
 __x64_sys_add_key+0xe4/0x150 security/keys/keyctl.c:74
 x64_sys_call+0xd3f/0x3ea0 arch/x86/include/generated/asm/syscalls_64.h:249
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x134/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Local variable dlen created at:
 encrypted_key_alloc+0x4f/0xa70 security/keys/encrypted-keys/encrypted.c:586
 encrypted_instantiate+0x45e/0x3220 security/keys/encrypted-keys/encrypted.c:812

CPU: 1 UID: 0 PID: 6291 Comm: syz.0.346 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
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