Re: Bad virt_to_phys since commit 54c7a8916a887f35
From: Mike Rapoport
Date: Thu May 16 2019 - 10:15:24 EST
On Thu, May 16, 2019 at 02:41:06PM +0100, Mark Rutland wrote:
> On Thu, May 16, 2019 at 02:38:20PM +0100, Mark Rutland wrote:
> > Hi,
> >
> > Since commit:
> >
> > 54c7a8916a887f35 ("initramfs: free initrd memory if opening /initrd.image fails")
>
> Ugh, I dropped a paragarph here.
>
> Since that commit, I'm seeing a boot-time splat on arm64 when using
> CONFIG_DEBUG_VIRTUAL. I'm running an arm64 syzkaller instance, and this
> kills the VM, preventing further testing, which is unfortunate.
>
> Mark.
>
> > IIUC prior to that commit, we'd only attempt to free an intird if we had
> > one, whereas now we do so unconditionally. AFAICT, in this case
> > initrd_start has not been initialized (I'm not using an initrd or
> > initramfs on my system), so we end up trying virt_to_phys() on a bogus
> > VA in free_initrd_mem().
> >
> > Any ideas on the right way to fix this?
If I remember correctly, initrd_start would be 0 unless explicitly set by
the arch setup code, so something like this could work:
diff --git a/init/initramfs.c b/init/initramfs.c
index 435a428c2af1..05fe60437796 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -529,6 +529,9 @@ extern unsigned long __initramfs_size;
void __weak free_initrd_mem(unsigned long start, unsigned long end)
{
+ if (!start)
+ return;
+
free_reserved_area((void *)start, (void *)end, POISON_FREE_INITMEM,
"initrd");
}
> >
> > Thanks,
> > Mark.
> >
> > [ 5.251023][ T1] ------------[ cut here ]------------
> > [ 5.252465][ T1] virt_to_phys used for non-linear address: (____ptrval____) (0x0)
> > [ 5.254388][ T1] WARNING: CPU: 0 PID: 1 at arch/arm64/mm/physaddr.c:15 __virt_to_phys+0x88/0xb8
> > [ 5.256473][ T1] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.1.0-11058-g83f3ef3 #4
> > [ 5.258513][ T1] Hardware name: linux,dummy-virt (DT)
> > [ 5.259923][ T1] pstate: 80400005 (Nzcv daif +PAN -UAO)
> > [ 5.261375][ T1] pc : __virt_to_phys+0x88/0xb8
> > [ 5.262623][ T1] lr : __virt_to_phys+0x88/0xb8
> > [ 5.263879][ T1] sp : ffff80000be4fc60
> > [ 5.264941][ T1] x29: ffff80000be4fc60 x28: 0000000040000000
> > [ 5.266522][ T1] x27: ffff200015445000 x26: 0000000000000000
> > [ 5.268112][ T1] x25: 0000000000000000 x24: ffff2000163e0000
> > [ 5.269691][ T1] x23: ffff2000163e0440 x22: ffff2000163e0000
> > [ 5.271270][ T1] x21: ffff2000163e0400 x20: 0000000000000000
> > [ 5.272860][ T1] x19: 0000000000000000 x18: ffff200016aa0f80
> > [ 5.274430][ T1] x17: ffff2000153a0000 x16: 00000000f2000000
> > [ 5.276018][ T1] x15: 1fffe40002d5560d x14: 1ffff00007716109
> > [ 5.277596][ T1] x13: ffff200016e17000 x12: ffff040002a83fd9
> > [ 5.279179][ T1] x11: 1fffe40002a83fd8 x10: ffff040002a83fd8
> > [ 5.280765][ T1] x9 : 1fffe40002a83fd8 x8 : dfff200000000000
> > [ 5.282343][ T1] x7 : ffff040002a83fd9 x6 : ffff20001541fec0
> > [ 5.283929][ T1] x5 : ffff80003b8b0040 x4 : 0000000000000000
> > [ 5.285509][ T1] x3 : ffff2000102c6504 x2 : ffff1000017c9f54
> > [ 5.287091][ T1] x1 : 15eab2dadba38000 x0 : 0000000000000000
> > [ 5.288678][ T1] Call trace:
> > [ 5.289532][ T1] __virt_to_phys+0x88/0xb8
> > [ 5.290701][ T1] free_initrd_mem+0x3c/0x50
> > [ 5.291894][ T1] populate_rootfs+0x2f4/0x358
> > [ 5.293123][ T1] do_one_initcall+0x568/0xb94
> > [ 5.294349][ T1] kernel_init_freeable+0xd44/0xe2c
> > [ 5.295695][ T1] kernel_init+0x14/0x1c0
> > [ 5.296814][ T1] ret_from_fork+0x10/0x1c
> > [ 5.297947][ T1] irq event stamp: 288672
> > [ 5.299069][ T1] hardirqs last enabled at (288671): [<ffff2000102c4cac>] console_unlock+0x89c/0xe50
> > [ 5.301521][ T1] hardirqs last disabled at (288672): [<ffff2000100823e0>] do_debug_exception+0x268/0x3e0
> > [ 5.304061][ T1] softirqs last enabled at (288668): [<ffff2000100835e0>] __do_softirq+0xa38/0xf48
> > [ 5.306457][ T1] softirqs last disabled at (288653): [<ffff2000101ac994>] irq_exit+0x2a4/0x318
> > [ 5.308777][ T1] ---[ end trace 3cf83e3c184a4d3e ]---
>
--
Sincerely yours,
Mike.