Re: [PATCH v2 2/2] x86/mm/sme: fix the kdump kernel breakage on SME system when CONFIG_IMA_KEXEC=y

From: Tom Lendacky
Date: Mon Sep 09 2024 - 10:54:02 EST

On 8/29/24 05:40, Baoquan He wrote:
> Recently, it's reported that kdump kernel is broken during bootup on
> SME system when CONFIG_IMA_KEXEC=y. When debugging, I noticed this
> can be traced back to commit ("b69a2afd5afc x86/kexec: Carry forward
> IMA measurement log on kexec"). Just nobody ever tested it on SME
> system when enabling CONFIG_IMA_KEXEC.
>
> --------------------------------------------------
> ima: No TPM chip found, activating TPM-bypass!
> Loading compiled-in module X.509 certificates
> Loaded X.509 cert 'Build time autogenerated kernel key: 18ae0bc7e79b64700122bb1d6a904b070fef2656'
> ima: Allocated hash algorithm: sha256
> Oops: general protection fault, probably for non-canonical address 0xcfacfdfe6660003e: 0000 [#1] PREEMPT SMP NOPTI
> CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.11.0-rc2+ #14
> Hardware name: Dell Inc. PowerEdge R7425/02MJ3T, BIOS 1.20.0 05/03/2023
> RIP: 0010:ima_restore_measurement_list+0xdc/0x420
> Code: ff 48 c7 85 10 ff ff ff 00 00 00 00 48 c7 85 18 ff ff ff 00 00 00 00 48 85 f6 0f 84 09 03 00 00 48 83 fa 17 0f 86 ff 02 00 00 <66> 83 3e 01 49 89 f4 0f 85 90 94 7d 00 48 83 7e 10 ff 0f 84 74 94
> RSP: 0018:ffffc90000053c80 EFLAGS: 00010286
> RAX: 0000000000000000 RBX: ffffc90000053d03 RCX: 0000000000000000
> RDX: e48066052d5df359 RSI: cfacfdfe6660003e RDI: cfacfdfe66600056
> RBP: ffffc90000053d80 R08: 0000000000000000 R09: ffffffff82de1a88
> R10: ffffc90000053da0 R11: 0000000000000003 R12: 00000000000001a4
> R13: ffffc90000053df0 R14: 0000000000000000 R15: 0000000000000000
> FS: 0000000000000000(0000) GS:ffff888040200000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f2c744050e8 CR3: 000080004110e000 CR4: 00000000003506b0
> Call Trace:
> <TASK>
> ? show_trace_log_lvl+0x1b0/0x2f0
> ? show_trace_log_lvl+0x1b0/0x2f0
> ? ima_load_kexec_buffer+0x6e/0xf0
> ? __die_body.cold+0x8/0x12
> ? die_addr+0x3c/0x60
> ? exc_general_protection+0x178/0x410
> ? asm_exc_general_protection+0x26/0x30
> ? ima_restore_measurement_list+0xdc/0x420
> ? vprintk_emit+0x1f0/0x270
> ? ima_load_kexec_buffer+0x6e/0xf0
> ima_load_kexec_buffer+0x6e/0xf0
> ima_init+0x52/0xb0
> ? __pfx_init_ima+0x10/0x10
> init_ima+0x26/0xc0
> ? __pfx_init_ima+0x10/0x10
> do_one_initcall+0x5b/0x300
> do_initcalls+0xdf/0x100
> ? __pfx_kernel_init+0x10/0x10
> kernel_init_freeable+0x147/0x1a0
> kernel_init+0x1a/0x140
> ret_from_fork+0x34/0x50
> ? __pfx_kernel_init+0x10/0x10
> ret_from_fork_asm+0x1a/0x30
> </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:ima_restore_measurement_list+0xdc/0x420
> Code: ff 48 c7 85 10 ff ff ff 00 00 00 00 48 c7 85 18 ff ff ff 00 00 00 00 48 85 f6 0f 84 09 03 00 00 48 83 fa 17 0f 86 ff 02 00 00 <66> 83 3e 01 49 89 f4 0f 85 90 94 7d 00 48 83 7e 10 ff 0f 84 74 94
> RSP: 0018:ffffc90000053c80 EFLAGS: 00010286
> RAX: 0000000000000000 RBX: ffffc90000053d03 RCX: 0000000000000000
> RDX: e48066052d5df359 RSI: cfacfdfe6660003e RDI: cfacfdfe66600056
> RBP: ffffc90000053d80 R08: 0000000000000000 R09: ffffffff82de1a88
> R10: ffffc90000053da0 R11: 0000000000000003 R12: 00000000000001a4
> R13: ffffc90000053df0 R14: 0000000000000000 R15: 0000000000000000
> FS: 0000000000000000(0000) GS:ffff888040200000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f2c744050e8 CR3: 000080004110e000 CR4: 00000000003506b0
> Kernel panic - not syncing: Fatal exception
> Kernel Offset: disabled
> Rebooting in 10 seconds..
>
> From debugging printing, the stored addr and size of ima_kexec buffer
> are not decrypted correctly like:
> ------
> ima: ima_load_kexec_buffer, buffer:0xcfacfdfe6660003e, size:0xe48066052d5df359
> ------
>
> There are three pieces of setup_data info passed to kexec/kdump kernel:
> SETUP_EFI, SETUP_IMA and SETUP_RNG_SEED. However, among them, only
> ima_kexec buffer suffered from the incorrect decryption. After
> debugging, it's because of the code bug in early_memremap_is_setup_data()
> where checking the embedded content inside setup_data takes wrong range
> calculation.
>
> The length of efi data, rng_seed and ima_kexec are 0x70, 0x20, 0x10,
> and the length of setup_data is 0x10. When checking if data is inside
> the embedded conent of setup_data, the starting address of efi data and
> rng_seed happened to land in the wrong calculated range. While the
> ima_kexec's starting address unluckily doesn't pass the checking, then
> error occurred.
>
> Here fix the code bug to make kexec/kdump kernel boot up successfully.
>
> And also fix the similar buggy code in memremap_is_setup_data() which
> are found out during code reviewing.

I think you should add something along the lines that the "len" variable
in struct setup_data is the length of the "data" field and does not
include the size of the struct, which is the reason for the miscalculation.

Otherwise:

Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx>

>
> Fixes: b3c72fc9a78e ("x86/boot: Introduce setup_indirect")
> Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
> ---
> arch/x86/mm/ioremap.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
> index f1ee8822ddf1..4cadc7ef1cb4 100644
> --- a/arch/x86/mm/ioremap.c
> +++ b/arch/x86/mm/ioremap.c
> @@ -657,7 +657,7 @@ static bool memremap_is_setup_data(resource_size_t phys_addr,
> paddr_next = data->next;
> len = data->len;
>
> - if ((phys_addr > paddr) && (phys_addr < (paddr + len))) {
> + if ((phys_addr > paddr) && (phys_addr < (paddr + sd_size + len))) {
> memunmap(data);
> return true;
> }
> @@ -721,7 +721,7 @@ static bool __init early_memremap_is_setup_data(resource_size_t phys_addr,
> paddr_next = data->next;
> len = data->len;
>
> - if ((phys_addr > paddr) && (phys_addr < (paddr + len))) {
> + if ((phys_addr > paddr) && (phys_addr < (paddr + sd_size + len))) {
> early_memunmap(data, sizeof(*data));
> return true;
> }