CVE-2024-26695 in Linux
Summary
by MITRE • 04/03/2024
In the Linux kernel, the following vulnerability has been resolved:
crypto: ccp - Fix null pointer dereference in __sev_platform_shutdown_locked
The SEV platform device can be shutdown with a null psp_master, e.g., using DEBUG_TEST_DRIVER_REMOVE. Found using KASAN:
[ 137.148210] ccp 0000:23:00.1: enabling device (0000 -> 0002)
[ 137.162647] ccp 0000:23:00.1: no command queues available
[ 137.170598] ccp 0000:23:00.1: sev enabled
[ 137.174645] ccp 0000:23:00.1: psp enabled
[ 137.178890] general protection fault, probably for non-canonical address 0xdffffc000000001e: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC KASAN NOPTI
[ 137.182693] KASAN: null-ptr-deref in range [0x00000000000000f0-0x00000000000000f7]
[ 137.182693] CPU: 93 PID: 1 Comm: swapper/0 Not tainted 6.8.0-rc1+ #311
[ 137.182693] RIP: 0010:__sev_platform_shutdown_locked+0x51/0x180
[ 137.182693] Code: 08 80 3c 08 00 0f 85 0e 01 00 00 48 8b 1d 67 b6 01 08 48 b8 00 00 00 00 00 fc ff df 48 8d bb f0 00 00 00 48 89 f9 48 c1 e9 03 3c 01 00 0f 85 fe 00 00 00 48 8b 9b f0 00 00 00 48 85 db 74 2c
[ 137.182693] RSP: 0018:ffffc900000cf9b0 EFLAGS: 00010216
[ 137.182693] RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 000000000000001e
[ 137.182693] RDX: 0000000000000000 RSI: 0000000000000008 RDI: 00000000000000f0
[ 137.182693] RBP: ffffc900000cf9c8 R08: 0000000000000000 R09: fffffbfff58f5a66
[ 137.182693] R10: ffffc900000cf9c8 R11: ffffffffac7ad32f R12: ffff8881e5052c28
[ 137.182693] R13: ffff8881e5052c28 R14: ffff8881758e43e8 R15: ffffffffac64abf8
[ 137.182693] FS: 0000000000000000(0000) GS:ffff889de7000000(0000) knlGS:0000000000000000
[ 137.182693] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 137.182693] CR2: 0000000000000000 CR3: 0000001cf7c7e000 CR4: 0000000000350ef0
[ 137.182693] Call Trace:
[ 137.182693]
[ 137.182693] ? show_regs+0x6c/0x80
[ 137.182693] ? __die_body+0x24/0x70
[ 137.182693] ? die_addr+0x4b/0x80
[ 137.182693] ? exc_general_protection+0x126/0x230
[ 137.182693] ? asm_exc_general_protection+0x2b/0x30
[ 137.182693] ? __sev_platform_shutdown_locked+0x51/0x180
[ 137.182693] sev_firmware_shutdown.isra.0+0x1e/0x80
[ 137.182693] sev_dev_destroy+0x49/0x100
[ 137.182693] psp_dev_destroy+0x47/0xb0
[ 137.182693] sp_destroy+0xbb/0x240
[ 137.182693] sp_pci_remove+0x45/0x60
[ 137.182693] pci_device_remove+0xaa/0x1d0
[ 137.182693] device_remove+0xc7/0x170
[ 137.182693] really_probe+0x374/0xbe0
[ 137.182693] ? srso_return_thunk+0x5/0x5f
[ 137.182693] __driver_probe_device+0x199/0x460
[ 137.182693] driver_probe_device+0x4e/0xd0
[ 137.182693] __driver_attach+0x191/0x3d0
[ 137.182693] ? __pfx___driver_attach+0x10/0x10
[ 137.182693] bus_for_each_dev+0x100/0x190
[ 137.182693] ? __pfx_bus_for_each_dev+0x10/0x10
[ 137.182693] ? __kasan_check_read+0x15/0x20
[ 137.182693] ? srso_return_thunk+0x5/0x5f
[ 137.182693] ? _raw_spin_unlock+0x27/0x50
[ 137.182693] driver_attach+0x41/0x60
[ 137.182693] bus_add_driver+0x2a8/0x580
[ 137.182693] driver_register+0x141/0x480
[ 137.182693] __pci_register_driver+0x1d6/0x2a0
[ 137.182693] ? srso_return_thunk+0x5/0x5f
[ 137.182693] ? esrt_sysfs_init+0x1cd/0x5d0
[ 137.182693] ? __pfx_sp_mod_init+0x10/0x10
[ 137.182693] sp_pci_init+0x22/0x30
[ 137.182693] sp_mod_init+0x14/0x30
[ 137.182693] ? __pfx_sp_mod_init+0x10/0x10
[ 137.182693] do_one_initcall+0xd1/0x470
[ 137.182693] ? __pfx_do_one_initcall+0x10/0x10
[ 137.182693] ? parameq+0x80/0xf0
[ 137.182693] ? srso_return_thunk+0x5/0x5f
[ 137.182693] ? __kmalloc+0x3b0/0x4e0
[ 137.182693] ? kernel_init_freeable+0x92d/0x1050
[ 137.182693] ? kasan_populate_vmalloc_pte+0x171/0x190
[ 137.182693] ? srso_return_thunk+0x5/0x5f
[ 137.182693] kernel_init_freeable+0xa64/0x1050
[ 137.182693] ? __pfx_kernel_init+0x10/0x10
[ 137.182693] kernel_init+0x24/0x160
[ 137.182693] ? __switch_to_asm+0x3e/0x70
[ 137.182693] ret_from_fork+0x40/0x80
[ 137.182693] ? __pfx_kernel_init+0x1
---truncated---
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Analysis
by VulDB Data Team • 08/03/2025
The vulnerability CVE-2024-26695 resides within the Linux kernel's cryptographic subsystem, specifically in the Confidential Computing Platform (CCP) driver responsible for handling AMD Secure Encrypted Virtualization (SEV) functionality. This issue manifests as a null pointer dereference during the shutdown sequence of the SEV platform device, occurring when the psp_master structure is unexpectedly null. The flaw arises in the function __sev_platform_shutdown_locked, which is invoked during device removal operations, particularly under debug configurations involving DEBUG_TEST_DRIVER_REMOVE. The kernel's memory safety checker KASAN detects this condition and reports a general protection fault due to attempting to access memory through a null pointer, indicating a critical failure in the device cleanup logic. The vulnerability is rooted in an insufficient null check before dereferencing the psp_master pointer, which should be validated before use. According to CWE-476, this represents a null pointer dereference, a common class of vulnerabilities that can lead to system crashes or potential privilege escalation. The attack surface is primarily limited to systems utilizing SEV-enabled hardware and kernel configurations that include debugging features. The call trace demonstrates that the fault originates from a chain of function calls beginning with device removal and propagating through the SEV and PSP (Platform Security Processor) subsystems, ultimately failing in the shutdown handler. This vulnerability aligns with ATT&CK technique T1068, which involves local privilege escalation through kernel exploitation, though the current impact is limited to system stability. The fix involves adding a null check for the psp_master pointer before attempting to dereference it, ensuring the driver can gracefully handle cases where the platform security master structure is not initialized. The issue is particularly concerning in virtualized environments where SEV is used for confidential computing, as it can lead to denial of service or compromise of encrypted virtual machine workloads. Mitigation efforts should include updating to a patched kernel version that includes the null pointer validation fix, disabling debug driver removal features in production systems, and monitoring for potential exploitation attempts targeting this specific kernel subsystem. The vulnerability highlights the importance of robust error handling in kernel space, particularly in cryptographic and security-sensitive components where improper resource cleanup can have cascading effects on system integrity.