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

Baoquan He
2024-08-27T03:19:45Z

On 08/27/24 at 09:41am, Dave Young wrote:
> On Tue, 27 Aug 2024 at 09:39, Dave Young <dyoung@redhat.com> wrote:
> >
> > On Mon, 26 Aug 2024 at 22:24, Tom Lendacky <thomas.lendacky@amd.com> 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.
> > >
> > > > Signed-off-by: Baoquan He <bhe@redhat.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.
> >
> > I think here size should be sizeof(struct setup_data) instead like below:
> > if ((phys_addr > paddr) && (phys_addr < (paddr + sizeof(struct
> > setup_data) + len)))
>
> Hmm, strictly it should be (webmail wrapped the line, please ignore that):
> if ((phys_addr >= paddr) && (phys_addr < (paddr + sizeof(struct
> setup_data) + len)))
>
> >
> > Baoquan, does the above work?

Both of my change and above change work because they are almost equal. I
changed like below at the very beginning, but using 'size' is simpler.
Please see below comment.

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;
while (paddr) {
......
size = sizeof(*data); // size = sizeof(stuct setup_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?
> > >
> > > 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.
> > >
> > > Thanks,
> > > Tom
> > >
> > > > early_memunmap(data, sizeof(*data));
> > > > return true;
> > > > }
> > >
>