UBSan: Undefined Behavior in db_nextframe (2)

[syzbot <syzbot+d90ea4cd8be1624622e8%syzkaller.appspotmail.com@localhost>]

Hello,

syzbot found the following issue on:

HEAD commit:    f12342b7f87d dk(4): Assert about dk_openmask under the lock.
git tree:       netbsd
console output: https://syzkaller.appspot.com/x/log.txt?x=11eee50d080000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1420f906d33d9f1f
dashboard link: https://syzkaller.appspot.com/bug?extid=d90ea4cd8be1624622e8
compiler:       g++ (Debian 10.2.1-6) 10.2.1 20210110

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d90ea4cd8be1624622e8%syzkaller.appspotmail.com@localhost

[ 209.6097795] panic: LOCKDEBUG: Kernel lock error: _kernel_lock,265: spinout
[ 209.6097795] cpu0: Begin traceback...
[ 209.6271147] vpanic() at netbsd:vpanic+0x2f2 sys/kern/subr_prf.c:293
[ 209.6771185] panic() at netbsd:panic+0x49 sys/kern/subr_prf.c:1033
[ 209.7071157] lockdebug_abort1() at netbsd:lockdebug_abort1+0x194 lockdebug_abort1 sys/kern/subr_lockdebug.c:790 [inline]
[ 209.7071157] lockdebug_abort1() at netbsd:lockdebug_abort1+0x194 sys/kern/subr_lockdebug.c:772
[ 209.7471171] _kernel_lock() at netbsd:_kernel_lock+0x4e5 sys/kern/kern_lock.c:265
[ 209.7771180] intr_biglock_wrapper() at netbsd:intr_biglock_wrapper+0x23 x86_curcpu sys/arch/amd64/compile/obj/GENERIC_SYZKALLER/./machine/cpu.h:56 [inline]
[ 209.7771180] intr_biglock_wrapper() at netbsd:intr_biglock_wrapper+0x23 sys/arch/x86/x86/intr.c:661
[ 209.7977178] Skipping crash dump on recursive panic
[ 209.7977178] panic: UBSan: Undefined Behavior in /syzkaller/managers/ci2-netbsd-kubsan/kernel/sys/arch/amd64/amd64/db_machdep.c:125:24, member access within misaligned address 0x1 for type 'struct x86_64_frame' which requires 8 byte alignment

[ 209.8242758] Faulted in mid-traceback; aborting...
[ 209.8288876] fatal breakpoint trap in supervisor mode
[ 209.8288876] trap type 1 code 0 rip 0xffffffff80221ab5 cs 0x8 rflags 0x246 cr2 0x776437f32000 ilevel 0x6 rsp 0xffffd28251454fb0
[ 209.8449947] curlwp 0xffffa962cd50ba80 pid 6034.6034 lowest kstack 0xffffd282514512c0
Stopped in pid 6034.6034 (syz-executor.4) at    netbsd:breakpoint+0x5:  leave
?
breakpoint() at netbsd:breakpoint+0x5
db_panic() at netbsd:db_panic+0xec sys/ddb/db_panic.c:69
vpanic() at netbsd:vpanic+0x2f2 sys/kern/subr_prf.c:293
Report() at netbsd:Report+0x3b sys/../common/lib/libc/misc/ubsan.c:1352
HandleTypeMismatch() at netbsd:HandleTypeMismatch+0xfc sys/../common/lib/libc/misc/ubsan.c:432
db_nextframe() at netbsd:db_nextframe+0x789 sys/arch/amd64/amd64/db_machdep.c:125
db_stack_trace_print() at netbsd:db_stack_trace_print+0x281 sys/arch/x86/x86/db_trace.c:277
db_panic() at netbsd:db_panic+0x9d x86_curcpu sys/arch/amd64/compile/obj/GENERIC_SYZKALLER/./machine/cpu.h:56 [inline]
db_panic() at netbsd:db_panic+0x9d sys/ddb/db_panic.c:59
vpanic() at netbsd:vpanic+0x2f2 sys/kern/subr_prf.c:293
panic() at netbsd:panic+0x49 sys/kern/subr_prf.c:1033
lockdebug_abort1() at netbsd:lockdebug_abort1+0x194 lockdebug_abort1 sys/kern/subr_lockdebug.c:790 [inline]
lockdebug_abort1() at netbsd:lockdebug_abort1+0x194 sys/kern/subr_lockdebug.c:772
_kernel_lock() at netbsd:_kernel_lock+0x4e5 sys/kern/kern_lock.c:265
intr_biglock_wrapper() at netbsd:intr_biglock_wrapper+0x23 x86_curcpu sys/arch/amd64/compile/obj/GENERIC_SYZKALLER/./machine/cpu.h:56 [inline]
intr_biglock_wrapper() at netbsd:intr_biglock_wrapper+0x23 sys/arch/x86/x86/intr.c:661
[ 209.8526098] Skipping crash dump on recursive panic
[ 209.8526098] panic: UBSan: Undefined Behavior in /syzkaller/managers/ci2-netbsd-kubsan/kernel/sys/arch/amd64/amd64/db_machdep.c:126:14, member access within misaligned address 0x1 for type 'struct x86_64_frame' which requires 8 byte alignment

[ 209.8526098] Faulted in mid-traceback; aborting...
[ 209.8526098] fatal breakpoint trap in supervisor mode
[ 209.8526098] trap type 1 code 0 rip 0xffffffff80221ab5 cs 0x8 rflags 0x246 cr2 0x776437f32000 ilevel 0x8 rsp 0xffffd28251453cb0
[ 209.8526098] curlwp 0xffffa962cd50ba80 pid 6034.6034 lowest kstack 0xffffd282514512c0
Stopped in pid 6034.6034 (syz-executor.4) at    netbsd:breakpoint+0x5:  leave


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