[syzbot] [kernel?] KMSAN: kernel-infoleak in irqentry_exit

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 670b77dfebe7 Merge tag 'usb-7.1-rc6' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10ca512e580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a0ca3b8cb3875012
dashboard link: https://syzkaller.appspot.com/bug?extid=185a631927096f9da2fc
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/30de8a17219b/disk-670b77df.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8ee3b0ab7b4b/vmlinux-670b77df.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ccbac9177b62/bzImage-670b77df.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+185a63...@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: kernel-infoleak in rseq_set_ids_get_csaddr include/linux/rseq_entry.h:502 [inline]
BUG: KMSAN: kernel-infoleak in rseq_update_usr include/linux/rseq_entry.h:536 [inline]
BUG: KMSAN: kernel-infoleak in rseq_exit_user_update include/linux/rseq_entry.h:644 [inline]
BUG: KMSAN: kernel-infoleak in __rseq_exit_to_user_mode_restart include/linux/rseq_entry.h:673 [inline]
BUG: KMSAN: kernel-infoleak in rseq_exit_to_user_mode_restart include/linux/rseq_entry.h:702 [inline]
BUG: KMSAN: kernel-infoleak in exit_to_user_mode_loop kernel/entry/common.c:100 [inline]
BUG: KMSAN: kernel-infoleak in __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
BUG: KMSAN: kernel-infoleak in irqentry_exit_to_user_mode_prepare include/linux/irq-entry-common.h:244 [inline]
BUG: KMSAN: kernel-infoleak in irqentry_exit_to_user_mode include/linux/irq-entry-common.h:315 [inline]
BUG: KMSAN: kernel-infoleak in irqentry_exit+0x48b/0xa00 kernel/entry/common.c:162
rseq_set_ids_get_csaddr include/linux/rseq_entry.h:502 [inline]
rseq_update_usr include/linux/rseq_entry.h:536 [inline]
rseq_exit_user_update include/linux/rseq_entry.h:644 [inline]
__rseq_exit_to_user_mode_restart include/linux/rseq_entry.h:673 [inline]
rseq_exit_to_user_mode_restart include/linux/rseq_entry.h:702 [inline]
exit_to_user_mode_loop kernel/entry/common.c:100 [inline]
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
irqentry_exit_to_user_mode_prepare include/linux/irq-entry-common.h:244 [inline]
irqentry_exit_to_user_mode include/linux/irq-entry-common.h:315 [inline]
irqentry_exit+0x48b/0xa00 kernel/entry/common.c:162
exc_page_fault+0x7e/0xb0 arch/x86/mm/fault.c:1530
asm_exc_page_fault+0x2b/0x30 arch/x86/include/asm/idtentry.h:618

Local variable end_time.i.i created at:
__do_sys_poll fs/select.c:1063 [inline]
__se_sys_poll fs/select.c:1060 [inline]
__x64_sys_poll+0x87/0x540 fs/select.c:1060
x64_sys_call+0x3130/0x3ea0 arch/x86/include/generated/asm/syscalls_64.h:8

Bytes 0-3 of 4 are uninitialized
Memory access of size 4 starts at ffff888119e3be88
Data copied to user address 00007fcc60203140

CPU: 1 UID: 0 PID: 5562 Comm: sshd-session Not tainted syzkaller #0 PREEMPT(lazy)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
=====================================================


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