WARNING in fpu__copy

[syzbot]

Hello,

syzkaller hit the following crash on
6084b576dca2e898f5c101baef151f7bfdbb606d
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.

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


netlink: 'syz-executor4': attribute type 2 has an invalid length.
device gre0 entered promiscuous mode
WARNING: CPU: 1 PID: 7913 at ./arch/x86/include/asm/fpu/internal.h:340
copy_xregs_to_kernel arch/x86/include/asm/fpu/internal.h:340 [inline]
WARNING: CPU: 1 PID: 7913 at ./arch/x86/include/asm/fpu/internal.h:340
copy_fpregs_to_fpstate arch/x86/include/asm/fpu/internal.h:413 [inline]
WARNING: CPU: 1 PID: 7913 at ./arch/x86/include/asm/fpu/internal.h:340
fpu__copy+0x385/0x390 arch/x86/kernel/fpu/core.c:212
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 7913 Comm: syz-executor2 Not tainted 4.15.0-rc3-next-20171214+
#67
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0xe9/0x14b lib/dump_stack.c:53
panic+0x10e/0x2f8 kernel/panic.c:183
__warn+0x14e/0x150 kernel/panic.c:547
report_bug+0x11e/0x1a0 lib/bug.c:184
fixup_bug.part.11+0x17/0x30 arch/x86/kernel/traps.c:177
fixup_bug arch/x86/kernel/traps.c:246 [inline]
do_error_trap+0x14a/0x180 arch/x86/kernel/traps.c:295
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:314
invalid_op+0x22/0x40 arch/x86/entry/entry_64.S:1079
RIP: 0010:copy_xregs_to_kernel arch/x86/include/asm/fpu/internal.h:340
[inline]
RIP: 0010:copy_fpregs_to_fpstate arch/x86/include/asm/fpu/internal.h:413
[inline]
RIP: 0010:fpu__copy+0x385/0x390 arch/x86/kernel/fpu/core.c:212
RSP: 0018:ffffc90000dc7d18 EFLAGS: 00010293
RAX: ffff88021516c380 RBX: ffff8801e1735580 RCX: ffffffff810d6e85
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8801e17355c0
RBP: ffffc90000dc7d38 R08: 000000000002dd38 R09: ffff8801e17355c0
R10: 0000000000000000 R11: 0000000000000000 R12: ffff88021516d780
R13: ffff8801e17355c0 R14: ffffc90000d94000 R15: ffff8801de73ea00
arch_dup_task_struct+0x27/0x30 arch/x86/kernel/process.c:100
dup_task_struct kernel/fork.c:786 [inline]
copy_process.part.35+0x161/0x2240 kernel/fork.c:1639
copy_process kernel/fork.c:1614 [inline]
_do_fork+0x122/0x880 kernel/fork.c:2095
SYSC_clone kernel/fork.c:2202 [inline]
SyS_clone+0x37/0x50 kernel/fork.c:2196
do_syscall_64+0x7f/0x270 arch/x86/entry/common.c:285
entry_SYSCALL64_slow_path+0x25/0x25
RIP: 0033:0x455399
RSP: 002b:0000000000a2f748 EFLAGS: 00000202 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007fcf3c9d9700 RCX: 0000000000455399
RDX: 00007fcf3c9d99d0 RSI: 00007fcf3c9d8db0 RDI: 00000000003d0f00
RBP: 0000000000a2f880 R08: 00007fcf3c9d9700 R09: 00007fcf3c9d9700
R10: 00007fcf3c9d99d0 R11: 0000000000000202 R12: 0000000000000000
R13: 0000000000a2f7ff R14: 00007fcf3c9d99c0 R15: 0000000000000002
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


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[Eric Biggers]

This last occurred on 10a7e9d849150a2879efc0b04d8a51068c9dd0c5 which was missing
commit 5663d8f9bbe4, so I'm guessing that fixed it:

#syz fix: kvm: x86: fix WARN due to uninitialized guest FPU state