Bad virt_to_phys since commit 54c7a8916a887f35

Bad virt_to_phys since commit 54c7a8916a887f35

[Mark Rutland]

Hi,

Since commit:

  54c7a8916a887f35 ("initramfs: free initrd memory if opening /initrd.image fails")

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?

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 ]---

Re: Bad virt_to_phys since commit 54c7a8916a887f35

[Mark Rutland]

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?
> 
> 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 ]---

Re: Bad virt_to_phys since commit 54c7a8916a887f35

[Steven Price]

On 16/05/2019 14:41, 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?

Your analysis looks right to me. In my review I'd managed to spot the
change in behaviour when CONFIG_INITRAMFS_FORCE is set (the initrd is
freed), but I'd overlooked what happens if initrd_start == 0 (the
non-existent initrd is attempted to be freed).

I suspect the following is sufficient to fix the problem:

----8<-----
diff --git a/init/initramfs.c b/init/initramfs.c
index 435a428c2af1..178130fd61c2 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -669,7 +669,7 @@ static int __init populate_rootfs(void)
 	 * If the initrd region is overlapped with crashkernel reserved region,
 	 * free only memory that is not part of crashkernel region.
 	 */
-	if (!do_retain_initrd && !kexec_free_initrd())
+	if (!do_retain_initrd && initrd_start && !kexec_free_initrd())
 		free_initrd_mem(initrd_start, initrd_end);
 	initrd_start = 0;
 	initrd_end = 0;

Re: Bad virt_to_phys since commit 54c7a8916a887f35

[Mark Rutland]

On Thu, May 16, 2019 at 03:05:31PM +0100, Steven Price wrote:
> On 16/05/2019 14:41, 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?
> 
> Your analysis looks right to me. In my review I'd managed to spot the
> change in behaviour when CONFIG_INITRAMFS_FORCE is set (the initrd is
> freed), but I'd overlooked what happens if initrd_start == 0 (the
> non-existent initrd is attempted to be freed).
> 
> I suspect the following is sufficient to fix the problem:
> 
> ----8<-----
> diff --git a/init/initramfs.c b/init/initramfs.c
> index 435a428c2af1..178130fd61c2 100644
> --- a/init/initramfs.c
> +++ b/init/initramfs.c
> @@ -669,7 +669,7 @@ static int __init populate_rootfs(void)
>  	 * If the initrd region is overlapped with crashkernel reserved region,
>  	 * free only memory that is not part of crashkernel region.
>  	 */
> -	if (!do_retain_initrd && !kexec_free_initrd())
> +	if (!do_retain_initrd && initrd_start && !kexec_free_initrd())
>  		free_initrd_mem(initrd_start, initrd_end);
>  	initrd_start = 0;
>  	initrd_end = 0;

That works for me. If you spin this as a real patch:

Tested-by: Mark Rutland <mark.rutland@arm.com>

As I mentioned, initrd_start has not been initialized at all, so I
suspect we should also update its declaration in init/do_mounts_initrd.c
such that it is guaranteed to be initialized to zero. We get away with
that today, but that won't necessarily hold with LTO and so on...

Thanks,
Mark.

Re: Bad virt_to_phys since commit 54c7a8916a887f35

[Steven Price]

On 16/05/2019 15:16, Mark Rutland wrote:
> On Thu, May 16, 2019 at 03:05:31PM +0100, Steven Price wrote:
>> On 16/05/2019 14:41, 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?
>>
>> Your analysis looks right to me. In my review I'd managed to spot the
>> change in behaviour when CONFIG_INITRAMFS_FORCE is set (the initrd is
>> freed), but I'd overlooked what happens if initrd_start == 0 (the
>> non-existent initrd is attempted to be freed).
>>
>> I suspect the following is sufficient to fix the problem:
>>
>> ----8<-----
>> diff --git a/init/initramfs.c b/init/initramfs.c
>> index 435a428c2af1..178130fd61c2 100644
>> --- a/init/initramfs.c
>> +++ b/init/initramfs.c
>> @@ -669,7 +669,7 @@ static int __init populate_rootfs(void)
>>  	 * If the initrd region is overlapped with crashkernel reserved region,
>>  	 * free only memory that is not part of crashkernel region.
>>  	 */
>> -	if (!do_retain_initrd && !kexec_free_initrd())
>> +	if (!do_retain_initrd && initrd_start && !kexec_free_initrd())
>>  		free_initrd_mem(initrd_start, initrd_end);
>>  	initrd_start = 0;
>>  	initrd_end = 0;
> 
> That works for me. If you spin this as a real patch:
> 
> Tested-by: Mark Rutland <mark.rutland@arm.com>
> 
> As I mentioned, initrd_start has not been initialized at all, so I
> suspect we should also update its declaration in init/do_mounts_initrd.c
> such that it is guaranteed to be initialized to zero. We get away with
> that today, but that won't necessarily hold with LTO and so on...

Well it's a global variable, so the C standard says it should be
initialised to 0...

I'll spin a real patch and add your Tested-by

Steve

Re: Bad virt_to_phys since commit 54c7a8916a887f35

[Mark Rutland]

On Thu, May 16, 2019 at 03:20:59PM +0100, Steven Price wrote:
> On 16/05/2019 15:16, Mark Rutland wrote:
> > On Thu, May 16, 2019 at 03:05:31PM +0100, Steven Price wrote:
> >> I suspect the following is sufficient to fix the problem:
> >>
> >> ----8<-----
> >> diff --git a/init/initramfs.c b/init/initramfs.c
> >> index 435a428c2af1..178130fd61c2 100644
> >> --- a/init/initramfs.c
> >> +++ b/init/initramfs.c
> >> @@ -669,7 +669,7 @@ static int __init populate_rootfs(void)
> >>  	 * If the initrd region is overlapped with crashkernel reserved region,
> >>  	 * free only memory that is not part of crashkernel region.
> >>  	 */
> >> -	if (!do_retain_initrd && !kexec_free_initrd())
> >> +	if (!do_retain_initrd && initrd_start && !kexec_free_initrd())
> >>  		free_initrd_mem(initrd_start, initrd_end);
> >>  	initrd_start = 0;
> >>  	initrd_end = 0;
> > 
> > That works for me. If you spin this as a real patch:
> > 
> > Tested-by: Mark Rutland <mark.rutland@arm.com>
> > 
> > As I mentioned, initrd_start has not been initialized at all, so I
> > suspect we should also update its declaration in init/do_mounts_initrd.c
> > such that it is guaranteed to be initialized to zero. We get away with
> > that today, but that won't necessarily hold with LTO and so on...
> 
> Well it's a global variable, so the C standard says it should be
> initialised to 0...

For some reason I was under the impression that wasn't guaranteed, but I
see that it is. Sorry for the noise.

> I'll spin a real patch and add your Tested-by

Great; thanks!

Mark.

Re: Bad virt_to_phys since commit 54c7a8916a887f35

[Will Deacon]

Hi Steven,

On Thu, May 16, 2019 at 03:20:59PM +0100, Steven Price wrote:
> I'll spin a real patch and add your Tested-by

Did you send this out? I can't spot it in my inbox.

Cheers,

Will

Re: Bad virt_to_phys since commit 54c7a8916a887f35

[Mike Rapoport]

On Thu, May 23, 2019 at 10:31:38AM +0100, Will Deacon wrote:
> Hi Steven,
> 
> On Thu, May 16, 2019 at 03:20:59PM +0100, Steven Price wrote:
> > I'll spin a real patch and add your Tested-by
> 
> Did you send this out? I can't spot it in my inbox.
 
https://lore.kernel.org/lkml/20190516143125.48948-1-steven.price@arm.com

And Andrew already took it to the -mm tree.

> Cheers,
> 
> Will
> 

-- 
Sincerely yours,
Mike.

Re: Bad virt_to_phys since commit 54c7a8916a887f35

[Steven Price]

On 23/05/2019 10:54, Mike Rapoport wrote:
> On Thu, May 23, 2019 at 10:31:38AM +0100, Will Deacon wrote:
>> Hi Steven,
>>
>> On Thu, May 16, 2019 at 03:20:59PM +0100, Steven Price wrote:
>>> I'll spin a real patch and add your Tested-by
>>
>> Did you send this out? I can't spot it in my inbox.
>  
> https://lore.kernel.org/lkml/20190516143125.48948-1-steven.price@arm.com
> 
> And Andrew already took it to the -mm tree.

And it's made its way to Linus' tree:
commit 5d59aa8f9ce972b472201aed86e904bb75879ff0

Steve

Re: Bad virt_to_phys since commit 54c7a8916a887f35

[Will Deacon]

On Thu, May 23, 2019 at 10:58:19AM +0100, Steven Price wrote:
> On 23/05/2019 10:54, Mike Rapoport wrote:
> > On Thu, May 23, 2019 at 10:31:38AM +0100, Will Deacon wrote:
> >> Hi Steven,
> >>
> >> On Thu, May 16, 2019 at 03:20:59PM +0100, Steven Price wrote:
> >>> I'll spin a real patch and add your Tested-by
> >>
> >> Did you send this out? I can't spot it in my inbox.
> >  
> > https://lore.kernel.org/lkml/20190516143125.48948-1-steven.price@arm.com
> > 
> > And Andrew already took it to the -mm tree.
> 
> And it's made its way to Linus' tree:
> commit 5d59aa8f9ce972b472201aed86e904bb75879ff0

Perfect, thanks. Sorry for the noise.

Will

Re: Bad virt_to_phys since commit 54c7a8916a887f35

[Mike Rapoport]

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.

Re: Bad virt_to_phys since commit 54c7a8916a887f35

[Mark Rutland]

On Thu, May 16, 2019 at 05:13:14PM +0300, Mike Rapoport wrote:
> 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");
>  }

I think this should work, given Steven's patch checks the same thing.

I don't have a preference as to which patch should be taken, so I'll
leave that to Christoph.

Thanks,
Mark.

Re: Bad virt_to_phys since commit 54c7a8916a887f35

[Christoph Hellwig]

On Thu, May 16, 2019 at 03:21:19PM +0100, Mark Rutland wrote:
> >  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");
> >  }
> 
> I think this should work, given Steven's patch checks the same thing.
> 
> I don't have a preference as to which patch should be taken, so I'll
> leave that to Christoph.

We still have plenty of architectures not using the generic
free_initrd_mem, so checking it in the caller gives us better
coverage.