Re: [PATCH v2] of: check previous kernel's ima-kexec-buffer against memory bounds
Thanks for looking into this patch Rob, I have addressed your review comment in v3 of the patch posted at https://lore.kernel.org/all/20220531041446.3334259-1-vaib...@linux.ibm.com/ -- Cheers ~ Vaibhav
Re: [PATCH v2] of: check previous kernel's ima-kexec-buffer against memory bounds
On Tue, May 24, 2022 at 11:20:42AM +0530, Vaibhav Jain wrote:
> Presently ima_get_kexec_buffer() doesn't check if the previous kernel's
> ima-kexec-buffer lies outside the addressable memory range. This can result
> in a kernel panic if the new kernel is booted with 'mem=X' arg and the
> ima-kexec-buffer was allocated beyond that range by the previous kernel.
> The panic is usually of the form below:
>
> $ sudo kexec --initrd initrd vmlinux --append='mem=16G'
>
>
> BUG: Unable to handle kernel data access on read at 0xc000c01fff7f
> Faulting instruction address: 0xc0837974
> Oops: Kernel access of bad area, sig: 11 [#1]
>
> NIP [c0837974] ima_restore_measurement_list+0x94/0x6c0
> LR [c083b55c] ima_load_kexec_buffer+0xac/0x160
> Call Trace:
> [c371fa80] [c083b55c] ima_load_kexec_buffer+0xac/0x160
> [c371fb00] [c20512c4] ima_init+0x80/0x108
> [c371fb70] [c20514dc] init_ima+0x4c/0x120
> [c371fbf0] [c0012240] do_one_initcall+0x60/0x2c0
> [c371fcc0] [c2004ad0] kernel_init_freeable+0x344/0x3ec
> [c371fda0] [c00128a4] kernel_init+0x34/0x1b0
> [c371fe10] [c000ce64] ret_from_kernel_thread+0x5c/0x64
> Instruction dump:
> f92100b8 f92100c0 90e10090 910100a0 4182050c 282a0017 3bc0 40810330
> 7c0802a6 fb610198 7c9b2378 f80101d0 2c090001 40820614 e9240010
> ---[ end trace ]---
>
> Fix this issue by checking returned PFN range of previous kernel's
> ima-kexec-buffer with pfn_valid to ensure correct memory bounds.
>
> Fixes: 467d27824920 ("powerpc: ima: get the kexec buffer passed by the
> previous kernel")
> Cc: Frank Rowand
> Cc: Prakhar Srivastava
> Cc: Lakshmi Ramasubramanian
> Cc: Thiago Jung Bauermann
> Cc: Rob Herring
> Signed-off-by: Vaibhav Jain
>
> ---
> Changelog
> ==
>
> v2:
> * Instead of using memblock to determine the valid bounds use pfn_valid() to
> do
> so since memblock may not be available late after the kernel init. [ Mpe ]
> * Changed the patch prefix from 'powerpc' to 'of' [ Mpe ]
> * Updated the 'Fixes' tag to point to correct commit that introduced this
> function. [ Rob ]
> * Fixed some whitespace/tab issues in the patch description [ Rob ]
> * Added another check for checking ig 'tmp_size' for ima-kexec-buffer is > 0
> ---
> drivers/of/kexec.c | 17 +
> 1 file changed, 17 insertions(+)
>
> diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
> index 8d374cc552be..879e984fe901 100644
> --- a/drivers/of/kexec.c
> +++ b/drivers/of/kexec.c
> @@ -126,6 +126,7 @@ int ima_get_kexec_buffer(void **addr, size_t *size)
> {
> int ret, len;
> unsigned long tmp_addr;
> + unsigned int start_pfn, end_pfn;
> size_t tmp_size;
> const void *prop;
>
> @@ -140,6 +141,22 @@ int ima_get_kexec_buffer(void **addr, size_t *size)
> if (ret)
> return ret;
>
> + /* Do some sanity on the returned size for the ima-kexec buffer */
> + if (!tmp_size)
> + return -ENOENT;
> +
> + /*
> + * Calculate the PFNs for the buffer and ensure
> + * they are with in addressable memory.
> + */
> + start_pfn = PHYS_PFN(tmp_addr);
> + end_pfn = PHYS_PFN(tmp_addr + tmp_size - 1);
> + if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn)) {
pfn_valid() isn't necessarily RAM, only that you have a struct page
AIUI. Maybe page_is_ram() instead?
Thanks to Robin for this.
Rob
Re: [PATCH v2] of: check previous kernel's ima-kexec-buffer against memory bounds
Hi Ritesh,
thanks for looking into this patch,
Ritesh Harjani writes:
> Just a minor nit which I noticed.
>
> On 22/05/24 11:20AM, Vaibhav Jain wrote:
>> Presently ima_get_kexec_buffer() doesn't check if the previous kernel's
>> ima-kexec-buffer lies outside the addressable memory range. This can result
>> in a kernel panic if the new kernel is booted with 'mem=X' arg and the
>> ima-kexec-buffer was allocated beyond that range by the previous kernel.
>> The panic is usually of the form below:
>>
>> $ sudo kexec --initrd initrd vmlinux --append='mem=16G'
>>
>>
>> BUG: Unable to handle kernel data access on read at 0xc000c01fff7f
>> Faulting instruction address: 0xc0837974
>> Oops: Kernel access of bad area, sig: 11 [#1]
>>
>> NIP [c0837974] ima_restore_measurement_list+0x94/0x6c0
>> LR [c083b55c] ima_load_kexec_buffer+0xac/0x160
>> Call Trace:
>> [c371fa80] [c083b55c] ima_load_kexec_buffer+0xac/0x160
>> [c371fb00] [c20512c4] ima_init+0x80/0x108
>> [c371fb70] [c20514dc] init_ima+0x4c/0x120
>> [c371fbf0] [c0012240] do_one_initcall+0x60/0x2c0
>> [c371fcc0] [c2004ad0] kernel_init_freeable+0x344/0x3ec
>> [c371fda0] [c00128a4] kernel_init+0x34/0x1b0
>> [c371fe10] [c000ce64] ret_from_kernel_thread+0x5c/0x64
>> Instruction dump:
>> f92100b8 f92100c0 90e10090 910100a0 4182050c 282a0017 3bc0 40810330
>> 7c0802a6 fb610198 7c9b2378 f80101d0 2c090001 40820614 e9240010
>> ---[ end trace ]---
>>
>> Fix this issue by checking returned PFN range of previous kernel's
>> ima-kexec-buffer with pfn_valid to ensure correct memory bounds.
>>
>> Fixes: 467d27824920 ("powerpc: ima: get the kexec buffer passed by the
>> previous kernel")
>> Cc: Frank Rowand
>> Cc: Prakhar Srivastava
>> Cc: Lakshmi Ramasubramanian
>> Cc: Thiago Jung Bauermann
>> Cc: Rob Herring
>> Signed-off-by: Vaibhav Jain
>>
>> ---
>> Changelog
>> ==
>>
>> v2:
>> * Instead of using memblock to determine the valid bounds use pfn_valid() to
>> do
>> so since memblock may not be available late after the kernel init. [ Mpe ]
>> * Changed the patch prefix from 'powerpc' to 'of' [ Mpe ]
>> * Updated the 'Fixes' tag to point to correct commit that introduced this
>> function. [ Rob ]
>> * Fixed some whitespace/tab issues in the patch description [ Rob ]
>> * Added another check for checking ig 'tmp_size' for ima-kexec-buffer is > 0
>> ---
>> drivers/of/kexec.c | 17 +
>> 1 file changed, 17 insertions(+)
>>
>> diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
>> index 8d374cc552be..879e984fe901 100644
>> --- a/drivers/of/kexec.c
>> +++ b/drivers/of/kexec.c
>> @@ -126,6 +126,7 @@ int ima_get_kexec_buffer(void **addr, size_t *size)
>> {
>> int ret, len;
>> unsigned long tmp_addr;
>> +unsigned int start_pfn, end_pfn;
>
> ^^^ Shouldn't this be unsigned long?
Thanks for catching this. Yes that should be 'unsigned long'. Will
resend the patch with this fixed.
>
> -ritesh
>
>> size_t tmp_size;
>> const void *prop;
>>
>> @@ -140,6 +141,22 @@ int ima_get_kexec_buffer(void **addr, size_t *size)
>> if (ret)
>> return ret;
>>
>> +/* Do some sanity on the returned size for the ima-kexec buffer */
>> +if (!tmp_size)
>> +return -ENOENT;
>> +
>> +/*
>> + * Calculate the PFNs for the buffer and ensure
>> + * they are with in addressable memory.
>> + */
>> +start_pfn = PHYS_PFN(tmp_addr);
>> +end_pfn = PHYS_PFN(tmp_addr + tmp_size - 1);
>> +if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn)) {
>> +pr_warn("IMA buffer at 0x%lx, size = 0x%zx beyond memory\n",
>> +tmp_addr, tmp_size);
>> +return -EINVAL;
>> +}
>> +
>> *addr = __va(tmp_addr);
>> *size = tmp_size;
>>
>> --
>> 2.35.1
>>
--
Cheers
~ Vaibhav
Re: [PATCH v2] of: check previous kernel's ima-kexec-buffer against memory bounds
Just a minor nit which I noticed.
On 22/05/24 11:20AM, Vaibhav Jain wrote:
> Presently ima_get_kexec_buffer() doesn't check if the previous kernel's
> ima-kexec-buffer lies outside the addressable memory range. This can result
> in a kernel panic if the new kernel is booted with 'mem=X' arg and the
> ima-kexec-buffer was allocated beyond that range by the previous kernel.
> The panic is usually of the form below:
>
> $ sudo kexec --initrd initrd vmlinux --append='mem=16G'
>
>
> BUG: Unable to handle kernel data access on read at 0xc000c01fff7f
> Faulting instruction address: 0xc0837974
> Oops: Kernel access of bad area, sig: 11 [#1]
>
> NIP [c0837974] ima_restore_measurement_list+0x94/0x6c0
> LR [c083b55c] ima_load_kexec_buffer+0xac/0x160
> Call Trace:
> [c371fa80] [c083b55c] ima_load_kexec_buffer+0xac/0x160
> [c371fb00] [c20512c4] ima_init+0x80/0x108
> [c371fb70] [c20514dc] init_ima+0x4c/0x120
> [c371fbf0] [c0012240] do_one_initcall+0x60/0x2c0
> [c371fcc0] [c2004ad0] kernel_init_freeable+0x344/0x3ec
> [c371fda0] [c00128a4] kernel_init+0x34/0x1b0
> [c371fe10] [c000ce64] ret_from_kernel_thread+0x5c/0x64
> Instruction dump:
> f92100b8 f92100c0 90e10090 910100a0 4182050c 282a0017 3bc0 40810330
> 7c0802a6 fb610198 7c9b2378 f80101d0 2c090001 40820614 e9240010
> ---[ end trace ]---
>
> Fix this issue by checking returned PFN range of previous kernel's
> ima-kexec-buffer with pfn_valid to ensure correct memory bounds.
>
> Fixes: 467d27824920 ("powerpc: ima: get the kexec buffer passed by the
> previous kernel")
> Cc: Frank Rowand
> Cc: Prakhar Srivastava
> Cc: Lakshmi Ramasubramanian
> Cc: Thiago Jung Bauermann
> Cc: Rob Herring
> Signed-off-by: Vaibhav Jain
>
> ---
> Changelog
> ==
>
> v2:
> * Instead of using memblock to determine the valid bounds use pfn_valid() to
> do
> so since memblock may not be available late after the kernel init. [ Mpe ]
> * Changed the patch prefix from 'powerpc' to 'of' [ Mpe ]
> * Updated the 'Fixes' tag to point to correct commit that introduced this
> function. [ Rob ]
> * Fixed some whitespace/tab issues in the patch description [ Rob ]
> * Added another check for checking ig 'tmp_size' for ima-kexec-buffer is > 0
> ---
> drivers/of/kexec.c | 17 +
> 1 file changed, 17 insertions(+)
>
> diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
> index 8d374cc552be..879e984fe901 100644
> --- a/drivers/of/kexec.c
> +++ b/drivers/of/kexec.c
> @@ -126,6 +126,7 @@ int ima_get_kexec_buffer(void **addr, size_t *size)
> {
> int ret, len;
> unsigned long tmp_addr;
> + unsigned int start_pfn, end_pfn;
^^^ Shouldn't this be unsigned long?
-ritesh
> size_t tmp_size;
> const void *prop;
>
> @@ -140,6 +141,22 @@ int ima_get_kexec_buffer(void **addr, size_t *size)
> if (ret)
> return ret;
>
> + /* Do some sanity on the returned size for the ima-kexec buffer */
> + if (!tmp_size)
> + return -ENOENT;
> +
> + /*
> + * Calculate the PFNs for the buffer and ensure
> + * they are with in addressable memory.
> + */
> + start_pfn = PHYS_PFN(tmp_addr);
> + end_pfn = PHYS_PFN(tmp_addr + tmp_size - 1);
> + if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn)) {
> + pr_warn("IMA buffer at 0x%lx, size = 0x%zx beyond memory\n",
> + tmp_addr, tmp_size);
> + return -EINVAL;
> + }
> +
> *addr = __va(tmp_addr);
> *size = tmp_size;
>
> --
> 2.35.1
>
[PATCH v2] of: check previous kernel's ima-kexec-buffer against memory bounds
Presently ima_get_kexec_buffer() doesn't check if the previous kernel's
ima-kexec-buffer lies outside the addressable memory range. This can result
in a kernel panic if the new kernel is booted with 'mem=X' arg and the
ima-kexec-buffer was allocated beyond that range by the previous kernel.
The panic is usually of the form below:
$ sudo kexec --initrd initrd vmlinux --append='mem=16G'
BUG: Unable to handle kernel data access on read at 0xc000c01fff7f
Faulting instruction address: 0xc0837974
Oops: Kernel access of bad area, sig: 11 [#1]
NIP [c0837974] ima_restore_measurement_list+0x94/0x6c0
LR [c083b55c] ima_load_kexec_buffer+0xac/0x160
Call Trace:
[c371fa80] [c083b55c] ima_load_kexec_buffer+0xac/0x160
[c371fb00] [c20512c4] ima_init+0x80/0x108
[c371fb70] [c20514dc] init_ima+0x4c/0x120
[c371fbf0] [c0012240] do_one_initcall+0x60/0x2c0
[c371fcc0] [c2004ad0] kernel_init_freeable+0x344/0x3ec
[c371fda0] [c00128a4] kernel_init+0x34/0x1b0
[c371fe10] [c000ce64] ret_from_kernel_thread+0x5c/0x64
Instruction dump:
f92100b8 f92100c0 90e10090 910100a0 4182050c 282a0017 3bc0 40810330
7c0802a6 fb610198 7c9b2378 f80101d0 2c090001 40820614 e9240010
---[ end trace ]---
Fix this issue by checking returned PFN range of previous kernel's
ima-kexec-buffer with pfn_valid to ensure correct memory bounds.
Fixes: 467d27824920 ("powerpc: ima: get the kexec buffer passed by the previous
kernel")
Cc: Frank Rowand
Cc: Prakhar Srivastava
Cc: Lakshmi Ramasubramanian
Cc: Thiago Jung Bauermann
Cc: Rob Herring
Signed-off-by: Vaibhav Jain
---
Changelog
==
v2:
* Instead of using memblock to determine the valid bounds use pfn_valid() to do
so since memblock may not be available late after the kernel init. [ Mpe ]
* Changed the patch prefix from 'powerpc' to 'of' [ Mpe ]
* Updated the 'Fixes' tag to point to correct commit that introduced this
function. [ Rob ]
* Fixed some whitespace/tab issues in the patch description [ Rob ]
* Added another check for checking ig 'tmp_size' for ima-kexec-buffer is > 0
---
drivers/of/kexec.c | 17 +
1 file changed, 17 insertions(+)
diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
index 8d374cc552be..879e984fe901 100644
--- a/drivers/of/kexec.c
+++ b/drivers/of/kexec.c
@@ -126,6 +126,7 @@ int ima_get_kexec_buffer(void **addr, size_t *size)
{
int ret, len;
unsigned long tmp_addr;
+ unsigned int start_pfn, end_pfn;
size_t tmp_size;
const void *prop;
@@ -140,6 +141,22 @@ int ima_get_kexec_buffer(void **addr, size_t *size)
if (ret)
return ret;
+ /* Do some sanity on the returned size for the ima-kexec buffer */
+ if (!tmp_size)
+ return -ENOENT;
+
+ /*
+* Calculate the PFNs for the buffer and ensure
+* they are with in addressable memory.
+*/
+ start_pfn = PHYS_PFN(tmp_addr);
+ end_pfn = PHYS_PFN(tmp_addr + tmp_size - 1);
+ if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn)) {
+ pr_warn("IMA buffer at 0x%lx, size = 0x%zx beyond memory\n",
+ tmp_addr, tmp_size);
+ return -EINVAL;
+ }
+
*addr = __va(tmp_addr);
*size = tmp_size;
--
2.35.1
