assertion failed: !ret

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 7a1e025a vmm: reimplement the x86 instruction decoder
git tree: akaros
console output: https://syzkaller.appspot.com/x/log.txt?x=1396a5d0e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b018fab5edd31b3
dashboard link: https://syzkaller.appspot.com/bug?extid=638411bd4594d01e2d70

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+638411...@syzkaller.appspotmail.com

kernel panic at kern/src/syscall.c:898, from core 0: assertion failed: !ret
Stack Backtrace on Core 0:
#01 [<0xffffffffc200a7fc>] in backtrace at src/kdebug.c:235
#02 [<0xffffffffc2009f95>] in _panic at src/init.c:275
#03 [<0xffffffffc205a2f3>] in sys_fork at src/syscall.c:898
#04 [<0xffffffffc2059f29>] in syscall at src/syscall.c:2580
#05 [<0xffffffffc205aad8>] in run_local_syscall at src/syscall.c:2617
#06 [<0xffffffffc205b019>] in prep_syscalls at src/syscall.c:2637
#07 [<0xffffffffc20b6282>] in sysenter_callwrapper at arch/x86/trap.c:926


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