[BUG] uml panics with "Segfault with no mm" in v3.19-rc

From: Miklos Szeredi
Date: Wed Dec 10 2014 - 05:46:12 EST

The guilty commit is:

00f634bc522d "asm-generic: add generic futex for !CONFIG_SMP"

And the backtrace:

#0 0x00007ffff7866457 in kill () from /lib64/libc.so.6
#1 0x000000006002a454 in uml_abort () at arch/um/os-Linux/util.c:93
#2 0x000000006002a7e5 in os_dump_core () at arch/um/os-Linux/util.c:148
#3 0x000000006001b48a in panic_exit (self=<optimized out>, unused1=<optimized out>, unused2=<optimized out>) at arch/um/kernel/um_arch.c:240
#4 0x000000006004e4df in notifier_call_chain (nl=<optimized out>, val=6, v=0xffffffff, nr_to_call=-1, nr_calls=0x0) at kernel/notifier.c:93
#5 0x000000006004e558 in __atomic_notifier_call_chain (nr_calls=<optimized out>, nr_to_call=<optimized out>, v=<optimized out>, val=<optimized out>, nh=<optimized out>) at kernel/notifier.c:183
#6 atomic_notifier_call_chain (nh=<optimized out>, val=<optimized out>, v=<optimized out>) at kernel/notifier.c:193
#7 0x0000000060238570 in panic (fmt=<optimized out>) at kernel/panic.c:133
#8 0x000000006001ad91 in segv (fi=..., ip=1610803493, is_user=<optimized out>, regs=0x602c1840 <cpu0_irqstack+6208>) at arch/um/kernel/trap.c:218
#9 0x000000006001b0f8 in segv_handler (sig=<optimized out>, unused_si=<optimized out>, regs=<optimized out>) at arch/um/kernel/trap.c:191
#10 0x0000000060029238 in sig_handler_common (sig=11, si=0x602c1d30 <cpu0_irqstack+7472>, mc=<optimized out>) at arch/um/os-Linux/signal.c:44
#11 0x0000000060029304 in sig_handler (sig=<optimized out>, si=<optimized out>, mc=<optimized out>) at arch/um/os-Linux/signal.c:231
#12 0x0000000060028dfd in hard_handler (sig=<optimized out>, si=0x6, p=<optimized out>) at arch/um/os-Linux/signal.c:165
#13 <signal handler called>
#14 memcpy () at arch/x86/um/../lib/memcpy_64.S:160
#15 0x000000006001c13d in copy_from_user (to=0x61c49e28, from=<optimized out>, n=<optimized out>) at arch/um/kernel/skas/uaccess.c:145
#16 0x0000000060072618 in futex_atomic_cmpxchg_inatomic (newval=<optimized out>, oldval=<optimized out>, uaddr=<optimized out>, uval=<optimized out>) at include/asm-generic/futex.h:109
#17 cmpxchg_futex_value_locked (curval=0x61c49e28, uaddr=0x0, uval=<optimized out>, newval=<optimized out>) at kernel/futex.c:596
#18 0x0000000060008b70 in futex_detect_cmpxchg () at kernel/futex.c:3020
#19 futex_init () at kernel/futex.c:3043
#20 0x00000000600166ba in do_one_initcall (fn=0x60008adf <futex_init>) at init/main.c:791

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