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Message-ID: <Zs1FrZVuZK14Je7z@MiWiFi-R3L-srv>
Date: Tue, 27 Aug 2024 11:19:09 +0800
From: Baoquan He <bhe@...hat.com>
To: Tom Lendacky <thomas.lendacky@....com>
Cc: linux-kernel@...r.kernel.org, noodles@...com, x86@...nel.org,
lijiang@...hat.com, dyoung@...hat.com, kexec@...ts.infradead.org
Subject: Re: [PATCH] x86/mm/sme: fix the kdump kernel breakage on SME system
when CONFIG_IMA_KEXEC=y
On 08/26/24 at 09:24am, Tom Lendacky wrote:
> On 8/25/24 21:44, 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.
> >
> > Fixes: 8f716c9b5feb ("x86/mm: Add support to access boot related data in the clear")
>
> The check that was modified was added by:
> b3c72fc9a78e ("x86/boot: Introduce setup_indirect")
>
> The SETUP_INDIRECT patches seem to be the issue here.
Hmm, I didn't check it carefully, thanks for addding this info. While
after checking commit b3c72fc9a78e, I feel the adding code was trying to
fix your original early_memremap_is_setup_data(). Even though
SETUP_INDIRECT type of setup_data has been added, the original
early_memremap_is_setup_data() only check the starting address and
the content of struct setup_data, that's obviously wrong.
arch/x86/include/uapi/asm/setup_data.h:
/* extensible setup data list node */
struct setup_data {
__u64 next;
__u32 type;
__u32 len;
__u8 data[];
};
As you can see, the zero-length will embed the carried data which is
actually expected and adjacent to its carrier, the struct setup_data.
>
> > Signed-off-by: Baoquan He <bhe@...hat.com>
> > ---
> > arch/x86/mm/ioremap.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
> > index aa7d279321ea..7953c4a1d28d 100644
> > --- a/arch/x86/mm/ioremap.c
> > +++ b/arch/x86/mm/ioremap.c
> > @@ -717,7 +717,7 @@ 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 + size + len))) {
>
> I don't think this is correct. You are adding the requested size to the
> length of the setup data element. The length is the true length of the
> setup data and should not be increased.
Please see the inline comment among code lines.
static bool __init early_memremap_is_setup_data(resource_size_t phys_addr,
unsigned long size)
{
struct setup_indirect *indirect;
struct setup_data *data;
u64 paddr, paddr_next;
paddr = boot_params.hdr.setup_data; //paddr point at struct steup_data;
while (paddr) {
unsigned int len, size;
if (phys_addr == paddr) // check the starting addr of setup_data
return true;
data = early_memremap_decrypted(paddr, sizeof(*data));
if (!data) {
pr_warn("failed to early memremap setup_data entry\n");
return false;
}
size = sizeof(*data); //size is the length of struct setup_data
paddr_next = data->next;
len = data->len; // len is the length of carried data,
//e.g sizeof(ima_setup_data) if ima_kexec buffer
// or sizeof(struct setup_indirect) if
// it's SETUP_INDIRECT type. Note that SETUP_INDIRECT
//data is also setup_data info even
//though it's intermideate info.
//Here I check if phys_addr is inside (paddr, paddr + sizeof(struct setup_data) + len)
//means it check if phys_addr is inside struct
//setup_data or struct ima_setup_data if ima_kexec case.
if ((phys_addr > paddr) && (phys_addr < (paddr + size + len))) {
early_memunmap(data, sizeof(*data));
return true;
}
if (data->type == SETUP_INDIRECT) {
......
if (indirect->type != SETUP_INDIRECT) {
paddr = indirect->addr;
len = indirect->len;
}
// it's checking the indirect dat, and the paddr
// is adjusted here. Wondering if indirect data
//can be nested, e.g
//setup_data->indirect->indirect->acutal data
}
...
}
...
}
>
> It looks like there were some major changes to this function to support
> SETUP_INDIRECT. Is the IMA log setup data marked SETUP_INDIRECT?
No, ima_kexec buffer is marked as SETUP_IMA, it's not indirect data.
arch/x86/kernel/kexec-bzimage64.c:
bzImage64_load()
->setup_boot_parameters()
->setup_ima_state()
>
> It might be helpful to instrument the code to see exactly what is
> happening during the execution of that function for the IMA log address.
I almost have printed all needed information because kexec/kdump passed
three types of setup_data, but only ima_kexec buffer is not got right.
The behaviour is very bizarre at the beginning.
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