CVE-2025-39936

In the Linux kernel, the following vulnerability has been resolved:

crypto: ccp - Always pass in an error pointer to __sev_platform_shutdown_locked()

When

9770b428b1a2 ("crypto: ccp - Move dev_info/err messages for SEV/SNP init and shutdown")

moved the error messages dumping so that they don't need to be issued by

the callers, it missed the case where __sev_firmware_shutdown() calls

__sev_platform_shutdown_locked() with a NULL argument which leads to

a NULL ptr deref on the shutdown path, during suspend to disk:

#PF: supervisor read access in kernel mode

#PF: error_code(0x0000) - not-present page

PGD 0 P4D 0

Oops: Oops: 0000 [#1] SMP NOPTI

CPU: 0 UID: 0 PID: 983 Comm: hib.sh Not tainted 6.17.0-rc4+ #1 PREEMPT(voluntary)

Hardware name: Supermicro Super Server/H12SSL-i, BIOS 2.5 09/08/2022

RIP: 0010:__sev_platform_shutdown_locked.cold+0x0/0x21 [ccp]

That rIP is:

00000000000006fd <__sev_platform_shutdown_locked.cold>:

6fd: 8b 13 mov (%rbx),%edx

6ff: 48 8b 7d 00 mov 0x0(%rbp),%rdi

703: 89 c1 mov %eax,%ecx

Code: 74 05 31 ff 41 89 3f 49 8b 3e 89 ea 48 c7 c6 a0 8e 54 a0 41 bf 92 ff ff ff e8 e5 2e 09 e1 c6 05 2a d4 38 00 01 e9 26 af ff ff <8b> 13 48 8b 7d 00 89 c1 48 c7 c6 18 90 54 a0 89 44 24 04 e8 c1 2e

RSP: 0018:ffffc90005467d00 EFLAGS: 00010282

RAX: 00000000ffffff92 RBX: 0000000000000000 RCX: 0000000000000000

^^^^^^^^^^^^^^^^

and %rbx is nice and clean.

Call Trace:

<TASK>

__sev_firmware_shutdown.isra.0

sev_dev_destroy

psp_dev_destroy

sp_destroy

pci_device_shutdown

device_shutdown

kernel_power_off

hibernate.cold

state_store

kernfs_fop_write_iter

vfs_write

ksys_write

do_syscall_64

entry_SYSCALL_64_after_hwframe

Pass in a pointer to the function-local error var in the caller.

With that addressed, suspending the ccp shows the error properly at

least:

ccp 0000:47:00.1: sev command 0x2 timed out, disabling PSP

ccp 0000:47:00.1: SEV: failed to SHUTDOWN error 0x0, rc -110

SEV-SNP: Leaking PFN range 0x146800-0x146a00

SEV-SNP: PFN 0x146800 unassigned, dumping non-zero entries in 2M PFN region: [0x146800 - 0x146a00]

...

ccp 0000:47:00.1: SEV-SNP firmware shutdown failed, rc -16, error 0x0

ACPI: PM: Preparing to enter system sleep state S5

kvm: exiting hardware virtualization

reboot: Power down

Btw, this driver is crying to be cleaned up to pass in a proper I/O

struct which can be used to store information between the different

functions, otherwise stuff like that will happen in the future again.