x86/crash: fix crash_setup_memmap_entries() out-of-bounds access

x86/crash: fix crash_setup_memmap_entries() out-of-bounds access

[Mike Galbraith]

x86/crash: fix crash_setup_memmap_entries() KASAN vmalloc-out-of-bounds gripe

[   15.428011] BUG: KASAN: vmalloc-out-of-bounds in crash_setup_memmap_entries+0x17e/0x3a0
[   15.428018] Write of size 8 at addr ffffc90000426008 by task kexec/1187

(gdb) list *crash_setup_memmap_entries+0x17e
0xffffffff8107cafe is in crash_setup_memmap_entries (arch/x86/kernel/crash.c:322).
317                                      unsigned long long mend)
318     {
319             unsigned long start, end;
320
321             cmem->ranges[0].start = mstart;
322             cmem->ranges[0].end = mend;
323             cmem->nr_ranges = 1;
324
325             /* Exclude elf header region */
326             start = image->arch.elf_load_addr;
(gdb)

We're excluding two ranges, allocate the scratch space we need to do that.

Signed-off-by: Mike Galbraith <efault@gmx.de>
---
 arch/x86/kernel/crash.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -337,7 +337,7 @@ int crash_setup_memmap_entries(struct ki
 	struct crash_memmap_data cmd;
 	struct crash_mem *cmem;

-	cmem = vzalloc(sizeof(struct crash_mem));
+	cmem = vzalloc(sizeof(struct crash_mem)+(2*sizeof(struct crash_mem_range)));
 	if (!cmem)
 		return -ENOMEM;

Re: x86/crash: fix crash_setup_memmap_entries() out-of-bounds access

[Dave Young]

Hi Mike,

Thanks for the patch! I suggest always cc kexec list for kexec/kdump
patches.
On 04/15/21 at 07:56pm, Mike Galbraith wrote:
> x86/crash: fix crash_setup_memmap_entries() KASAN vmalloc-out-of-bounds gripe
> 
> [   15.428011] BUG: KASAN: vmalloc-out-of-bounds in crash_setup_memmap_entries+0x17e/0x3a0
> [   15.428018] Write of size 8 at addr ffffc90000426008 by task kexec/1187
> 
> (gdb) list *crash_setup_memmap_entries+0x17e
> 0xffffffff8107cafe is in crash_setup_memmap_entries (arch/x86/kernel/crash.c:322).
> 317                                      unsigned long long mend)
> 318     {
> 319             unsigned long start, end;
> 320
> 321             cmem->ranges[0].start = mstart;
> 322             cmem->ranges[0].end = mend;
> 323             cmem->nr_ranges = 1;
> 324
> 325             /* Exclude elf header region */
> 326             start = image->arch.elf_load_addr;
> (gdb)
> 
> We're excluding two ranges, allocate the scratch space we need to do that.

I think 1 range should be fine, have you tested 1?

The code is just excluding the elf header space which will be loaded
first before anything else so I assume it will be just at the start of
the crashkernel resource region.  Thus [a b] after exclude the start
part will be [c b].  But I have not read the code for long time, maybe I
need to double check.

But anyway 2 would be good since the code is obscure we can easily miss
it in the future.  See how other people think.

> 
> Signed-off-by: Mike Galbraith <efault@gmx.de>
> ---
>  arch/x86/kernel/crash.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- a/arch/x86/kernel/crash.c
> +++ b/arch/x86/kernel/crash.c
> @@ -337,7 +337,7 @@ int crash_setup_memmap_entries(struct ki
>  	struct crash_memmap_data cmd;
>  	struct crash_mem *cmem;
> 
> -	cmem = vzalloc(sizeof(struct crash_mem));
> +	cmem = vzalloc(sizeof(struct crash_mem)+(2*sizeof(struct crash_mem_range)));

Thanks for the patch, can you try below?
vzalloc(struct_size(cmem, ranges, 2));


>  	if (!cmem)
>  		return -ENOMEM;
> 
> 

Thanks
Dave

Re: x86/crash: fix crash_setup_memmap_entries() out-of-bounds access

[Mike Galbraith]

On Fri, 2021-04-16 at 19:07 +0800, Dave Young wrote:
>
> > We're excluding two ranges, allocate the scratch space we need to do that.
>
> I think 1 range should be fine, have you tested 1?

Have now, and vzalloc(struct_size(cmem, ranges, 1)) worked just fine.

	-Mike

Re: x86/crash: fix crash_setup_memmap_entries() out-of-bounds access

[Dave Young]

On 04/16/21 at 01:28pm, Mike Galbraith wrote:
> On Fri, 2021-04-16 at 19:07 +0800, Dave Young wrote:
> >
> > > We're excluding two ranges, allocate the scratch space we need to do that.
> >
> > I think 1 range should be fine, have you tested 1?
> 
> Have now, and vzalloc(struct_size(cmem, ranges, 1)) worked just fine.

Ok, thanks for your quick response.  Care to resend and cc x86 list and
Andrew?

Andrew usually takes core kexec/kdump fixes, x86 usually go through x86
maintainer.

Thanks
Dave

[patch] x86/crash: fix crash_setup_memmap_entries() out-of-bounds access

[Mike Galbraith]

[   15.428011] BUG: KASAN: vmalloc-out-of-bounds in crash_setup_memmap_entries+0x17e/0x3a0
[   15.428018] Write of size 8 at addr ffffc90000426008 by task kexec/1187

(gdb) list *crash_setup_memmap_entries+0x17e
0xffffffff8107cafe is in crash_setup_memmap_entries (arch/x86/kernel/crash.c:322).
317                                      unsigned long long mend)
318     {
319             unsigned long start, end;
320
321             cmem->ranges[0].start = mstart;
322             cmem->ranges[0].end = mend;
323             cmem->nr_ranges = 1;
324
325             /* Exclude elf header region */
326             start = image->arch.elf_load_addr;
(gdb)

Append missing struct crash_mem_range to cmem.

Signed-off-by: Mike Galbraith <efault@gmx.de>
---
 arch/x86/kernel/crash.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -337,7 +337,7 @@ int crash_setup_memmap_entries(struct ki
 	struct crash_memmap_data cmd;
 	struct crash_mem *cmem;

-	cmem = vzalloc(sizeof(struct crash_mem));
+	cmem = vzalloc(struct_size(cmem, ranges, 1));
 	if (!cmem)
 		return -ENOMEM;

Re: [patch] x86/crash: fix crash_setup_memmap_entries() out-of-bounds access

[Borislav Petkov]

On Fri, Apr 16, 2021 at 02:02:07PM +0200, Mike Galbraith wrote:
> [   15.428011] BUG: KASAN: vmalloc-out-of-bounds in crash_setup_memmap_entries+0x17e/0x3a0
> [   15.428018] Write of size 8 at addr ffffc90000426008 by task kexec/1187
> 
> (gdb) list *crash_setup_memmap_entries+0x17e
> 0xffffffff8107cafe is in crash_setup_memmap_entries (arch/x86/kernel/crash.c:322).
> 317                                      unsigned long long mend)
> 318     {
> 319             unsigned long start, end;
> 320
> 321             cmem->ranges[0].start = mstart;
> 322             cmem->ranges[0].end = mend;
> 323             cmem->nr_ranges = 1;
> 324
> 325             /* Exclude elf header region */
> 326             start = image->arch.elf_load_addr;
> (gdb)
> 
> Append missing struct crash_mem_range to cmem.

This is winning this year's contest for most laconic patch commit
message! :-)

Please be more verbose and structure your commit message like this:

Problem is A.

It happens because of B.

Fix it by doing C.

(Potentially do D).

For more detailed info, see
Documentation/process/submitting-patches.rst, Section "2) Describe your
changes".

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [patch] x86/crash: fix crash_setup_memmap_entries() out-of-bounds access

[Mike Galbraith]

On Fri, 2021-04-16 at 14:16 +0200, Borislav Petkov wrote:
>
> Please be more verbose and structure your commit message like this:

Hrmph, I thought it was too verbose for dinky one-liner if anything.  I
showed the complaint along with an 8x10 color glossy crime scene photo,
then explained why it happened and what to do about it with a perhaps
terse but perfectly clear sentence.

	-Mike

Re: [patch] x86/crash: fix crash_setup_memmap_entries() out-of-bounds access

[Borislav Petkov]

On Fri, Apr 16, 2021 at 03:16:07PM +0200, Mike Galbraith wrote:
> On Fri, 2021-04-16 at 14:16 +0200, Borislav Petkov wrote:
> >
> > Please be more verbose and structure your commit message like this:
> 
> Hrmph, I thought it was too verbose for dinky one-liner if anything. 

Please look at how other commit messages in tip have free text - not
only tools output.

Also, this looks like a fix for some previous commit. Please dig out
which commit introduced the issue and put its commit ID in a Fixes: tag
above your S-o-B.

If you don't have time or desire to do that, you can say so and I'll do
it myself when I get a chance.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [patch] x86/crash: fix crash_setup_memmap_entries() out-of-bounds access

[Mike Galbraith]

On Fri, 2021-04-16 at 16:44 +0200, Borislav Petkov wrote:
> On Fri, Apr 16, 2021 at 03:16:07PM +0200, Mike Galbraith wrote:
> > On Fri, 2021-04-16 at 14:16 +0200, Borislav Petkov wrote:
> > >
> > > Please be more verbose and structure your commit message like this:
> >
> > Hrmph, I thought it was too verbose for dinky one-liner if anything.
>
> Please look at how other commit messages in tip have free text - not
> only tools output.
>
> Also, this looks like a fix for some previous commit. Please dig out
> which commit introduced the issue and put its commit ID in a Fixes: tag
> above your S-o-B.
>
> If you don't have time or desire to do that, you can say so and I'll do
> it myself when I get a chance.

Ok, bin it for the nonce.

	-Mike

Re: [patch] x86/crash: fix crash_setup_memmap_entries() out-of-bounds access

[Thomas Gleixner]

On Fri, Apr 16 2021 at 17:13, Mike Galbraith wrote:
> On Fri, 2021-04-16 at 16:44 +0200, Borislav Petkov wrote:
>> On Fri, Apr 16, 2021 at 03:16:07PM +0200, Mike Galbraith wrote:
>> > On Fri, 2021-04-16 at 14:16 +0200, Borislav Petkov wrote:
>> > >
>> > > Please be more verbose and structure your commit message like this:
>> >
>> > Hrmph, I thought it was too verbose for dinky one-liner if anything.
>>
>> Please look at how other commit messages in tip have free text - not
>> only tools output.
>>
>> Also, this looks like a fix for some previous commit. Please dig out
>> which commit introduced the issue and put its commit ID in a Fixes: tag
>> above your S-o-B.
>>
>> If you don't have time or desire to do that, you can say so and I'll do
>> it myself when I get a chance.
>
> Ok, bin it for the nonce.

Can all of you involved stop this sandpit fight and do something useful
to fix that obvious bug already?

OMG

Re: [patch] x86/crash: fix crash_setup_memmap_entries() out-of-bounds access

[Mike Galbraith]

On Fri, 2021-04-16 at 23:44 +0200, Thomas Gleixner wrote:
>
> Can all of you involved stop this sandpit fight and do something useful
> to fix that obvious bug already?

?? We're not fighting afaik.  Boris hated my changelog enough to offer
to write a better one, and I'm fine with that.  It's a seven year old
*latent* buglet of microscopic proportions, hardly a pressing issue.

	-Mike

Re: [patch] x86/crash: fix crash_setup_memmap_entries() out-of-bounds access

[Borislav Petkov]

Here's an attempt to explain what this fixes:

---
From: Mike Galbraith <efault@gmx.de>
Date: Fri, 16 Apr 2021 14:02:07 +0200
Subject: [PATCH] x86/crash: Fix crash_setup_memmap_entries() out-of-bounds
 access

Commit in Fixes: added support for kexec-ing a kernel on panic using a
new system call. As part of it, it does prepare a memory map for the new
kernel.

However, while doing so, it wrongly accesses memory it has not
allocated: it accesses the first element of the cmem->ranges[] array in
memmap_exclude_ranges() but it has not allocated the memory for it in
crash_setup_memmap_entries(). As KASAN reports:

  BUG: KASAN: vmalloc-out-of-bounds in crash_setup_memmap_entries+0x17e/0x3a0
  Write of size 8 at addr ffffc90000426008 by task kexec/1187

  (gdb) list *crash_setup_memmap_entries+0x17e
  0xffffffff8107cafe is in crash_setup_memmap_entries (arch/x86/kernel/crash.c:322).
  317                                      unsigned long long mend)
  318     {
  319             unsigned long start, end;
  320
  321             cmem->ranges[0].start = mstart;
  322             cmem->ranges[0].end = mend;
  323             cmem->nr_ranges = 1;
  324
  325             /* Exclude elf header region */
  326             start = image->arch.elf_load_addr;
  (gdb)

Make sure the ranges array becomes a single element allocated.

 [ bp: Write a proper commit message. ]

Fixes: dd5f726076cc ("kexec: support for kexec on panic using new system call")
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/725fa3dc1da2737f0f6188a1a9701bead257ea9d.camel@gmx.de
---
 arch/x86/kernel/crash.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index a8f3af257e26..b1deacbeb266 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -337,7 +337,7 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params)
 	struct crash_memmap_data cmd;
 	struct crash_mem *cmem;
 
-	cmem = vzalloc(sizeof(struct crash_mem));
+	cmem = vzalloc(struct_size(cmem, ranges, 1));
 	if (!cmem)
 		return -ENOMEM;
 
-- 
2.29.2

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [patch] x86/crash: fix crash_setup_memmap_entries() out-of-bounds access

[DaveYoung]

On 04/19/21 at 10:52am, Borislav Petkov wrote:
> Here's an attempt to explain what this fixes:
> 
> ---
> From: Mike Galbraith <efault@gmx.de>
> Date: Fri, 16 Apr 2021 14:02:07 +0200
> Subject: [PATCH] x86/crash: Fix crash_setup_memmap_entries() out-of-bounds
>  access
> 
> Commit in Fixes: added support for kexec-ing a kernel on panic using a
> new system call. As part of it, it does prepare a memory map for the new
> kernel.
> 
> However, while doing so, it wrongly accesses memory it has not
> allocated: it accesses the first element of the cmem->ranges[] array in
> memmap_exclude_ranges() but it has not allocated the memory for it in
> crash_setup_memmap_entries(). As KASAN reports:
> 
>   BUG: KASAN: vmalloc-out-of-bounds in crash_setup_memmap_entries+0x17e/0x3a0
>   Write of size 8 at addr ffffc90000426008 by task kexec/1187
> 
>   (gdb) list *crash_setup_memmap_entries+0x17e
>   0xffffffff8107cafe is in crash_setup_memmap_entries (arch/x86/kernel/crash.c:322).
>   317                                      unsigned long long mend)
>   318     {
>   319             unsigned long start, end;
>   320
>   321             cmem->ranges[0].start = mstart;
>   322             cmem->ranges[0].end = mend;
>   323             cmem->nr_ranges = 1;
>   324
>   325             /* Exclude elf header region */
>   326             start = image->arch.elf_load_addr;
>   (gdb)
> 
> Make sure the ranges array becomes a single element allocated.
> 
>  [ bp: Write a proper commit message. ]

Reviewed-by: Dave Young <dyoung@redhat.com>

> 
> Fixes: dd5f726076cc ("kexec: support for kexec on panic using new system call")
> Signed-off-by: Mike Galbraith <efault@gmx.de>
> Signed-off-by: Borislav Petkov <bp@suse.de>
> Link: https://lkml.kernel.org/r/725fa3dc1da2737f0f6188a1a9701bead257ea9d.camel@gmx.de
> ---
>  arch/x86/kernel/crash.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> index a8f3af257e26..b1deacbeb266 100644
> --- a/arch/x86/kernel/crash.c
> +++ b/arch/x86/kernel/crash.c
> @@ -337,7 +337,7 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params)
>  	struct crash_memmap_data cmd;
>  	struct crash_mem *cmem;
>  
> -	cmem = vzalloc(sizeof(struct crash_mem));
> +	cmem = vzalloc(struct_size(cmem, ranges, 1));
>  	if (!cmem)
>  		return -ENOMEM;
>  
> -- 
> 2.29.2
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> https://people.kernel.org/tglx/notes-about-netiquette
> 

Thanks
Dave

[tip: x86/urgent] x86/crash: Fix crash_setup_memmap_entries() out-of-bounds access

[tip-bot2 for Mike Galbraith]

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     5849cdf8c120e3979c57d34be55b92d90a77a47e
Gitweb:        https://git.kernel.org/tip/5849cdf8c120e3979c57d34be55b92d90a77a47e
Author:        Mike Galbraith <efault@gmx.de>
AuthorDate:    Fri, 16 Apr 2021 14:02:07 +02:00
Committer:     Borislav Petkov <bp@suse.de>
CommitterDate: Tue, 20 Apr 2021 17:32:46 +02:00

x86/crash: Fix crash_setup_memmap_entries() out-of-bounds access

Commit in Fixes: added support for kexec-ing a kernel on panic using a
new system call. As part of it, it does prepare a memory map for the new
kernel.

However, while doing so, it wrongly accesses memory it has not
allocated: it accesses the first element of the cmem->ranges[] array in
memmap_exclude_ranges() but it has not allocated the memory for it in
crash_setup_memmap_entries(). As KASAN reports:

  BUG: KASAN: vmalloc-out-of-bounds in crash_setup_memmap_entries+0x17e/0x3a0
  Write of size 8 at addr ffffc90000426008 by task kexec/1187

  (gdb) list *crash_setup_memmap_entries+0x17e
  0xffffffff8107cafe is in crash_setup_memmap_entries (arch/x86/kernel/crash.c:322).
  317                                      unsigned long long mend)
  318     {
  319             unsigned long start, end;
  320
  321             cmem->ranges[0].start = mstart;
  322             cmem->ranges[0].end = mend;
  323             cmem->nr_ranges = 1;
  324
  325             /* Exclude elf header region */
  326             start = image->arch.elf_load_addr;
  (gdb)

Make sure the ranges array becomes a single element allocated.

 [ bp: Write a proper commit message. ]

Fixes: dd5f726076cc ("kexec: support for kexec on panic using new system call")
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Dave Young <dyoung@redhat.com>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/725fa3dc1da2737f0f6188a1a9701bead257ea9d.camel@gmx.de
---
 arch/x86/kernel/crash.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index a8f3af2..b1deacb 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -337,7 +337,7 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params)
 	struct crash_memmap_data cmd;
 	struct crash_mem *cmem;
 
-	cmem = vzalloc(sizeof(struct crash_mem));
+	cmem = vzalloc(struct_size(cmem, ranges, 1));
 	if (!cmem)
 		return -ENOMEM;