HIGH
crypto CCP PDH Export Overflow
CVE-2026-31698
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
KernelScan AI7.1HIGH
01Description
In the Linux kernel, the following vulnerability has been resolved: crypto: ccp: Don't attempt to copy PDH cert to userspace if PSP command failed When retrieving the PDH cert, don't attempt to copy the blobs to userspace if the firmware command failed. If the failure was due to an invalid length, i.e. the userspace buffer+length was too small, copying the number of bytes _firmware_ requires will overflow the kernel-allocated buffer and leak data to userspace. BUG: KASAN: slab-out-of-bounds in instrument_copy_to_user ../include/linux/instrumented.h:129 [inline] BUG: KASAN: slab-out-of-bounds in _inline_copy_to_user ../include/linux/uaccess.h:205 [inline] BUG: KASAN: slab-out-of-bounds in _copy_to_user+0x66/0xa0 ../lib/usercopy.c:26 Read of size 2084 at addr ffff8885c4ab8aa0 by task syz.0.186/21033 CPU: 51 UID: 0 PID: 21033 Comm: syz.0.186 Tainted: G U O 7.0.0-smp-DEV #28 PREEMPTLAZY Tainted: [U]=USER, [O]=OOT_MODULE Hardware name: Google, Inc. Arcadia_IT_80/Arcadia_IT_80, BIOS 34.84.12-0 11/17/2025 Call Trace: <TASK> dump_stack_lvl+0xc5/0x110 ../lib/dump_stack.c:120 print_address_description ../mm/kasan/report.c:378 [inline] print_report+0xbc/0x260 ../mm/kasan/report.c:482 kasan_report+0xa2/0xe0 ../mm/kasan/report.c:595 check_region_inline ../mm/kasan/generic.c:-1 [inline] kasan_check_range+0x264/0x2c0 ../mm/kasan/generic.c:200 instrument_copy_to_user ../include/linux/instrumented.h:129 [inline] _inline_copy_to_user ../include/linux/uaccess.h:205 [inline] _copy_to_user+0x66/0xa0 ../lib/usercopy.c:26 copy_to_user ../include/linux/uaccess.h:236 [inline] sev_ioctl_do_pdh_export+0x3d3/0x7c0 ../drivers/crypto/ccp/sev-dev.c:2347 sev_ioctl+0x2a2/0x490 ../drivers/crypto/ccp/sev-dev.c:2568 vfs_ioctl ../fs/ioctl.c:51 [inline] __do_sys_ioctl ../fs/ioctl.c:597 [inline] __se_sys_ioctl+0x11d/0x1b0 ../fs/ioctl.c:583 do_syscall_x64 ../arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xe0/0x800 ../arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x76/0x7e </TASK> WARN if the driver says the command succeeded, but the firmware error code says otherwise, as __sev_do_cmd_locked() is expected to return -EIO on any firwmware error.
02KernelScan AI Analysis
Risk summary
An attacker with local access to the SEV device can trigger a buffer overflow by providing an undersized buffer to the PDH certificate export operation. This can lead to kernel memory disclosure to userspace, potentially exposing sensitive kernel data. The attack requires local access and the ability to interact with the SEV cryptographic coprocessor device.
Vulnerability analysis
Root Cause: The sev_ioctl_do_pdh_export function attempts to copy firmware response data to userspace even when the PSP firmware command fails. When the failure is due to insufficient buffer size, the firmware returns the required buffer size, but the kernel still tries to copy that many bytes from its smaller allocated buffer, causing an out-of-bounds read and potential information leak.
Attack Surface: Local attack surface through ioctl interface. Requires access to the SEV device file (/dev/sev) and ability to call the SEV_PDH_CERT_EXPORT ioctl. The vulnerability is triggered by providing an undersized buffer to the ioctl call.
Fix Mechanism: The patch adds a check to prevent copying data to userspace if the PSP command failed (ret != 0) or if there's a firmware error (argp->error != 0). It also adds a WARN_ON_ONCE to catch inconsistent states where the driver reports success but firmware reports an error.
03Fix Versions
| Branch | Fixed in | Patch commit |
|---|---|---|
| 5.10 | 5.10.258 | af67d35da744 |
| 5.15 | 5.15.209 | 854d7846e1d2 |
| 6.1 | 6.1.175 | 25d9b3446001 |
| 6.12 | 6.12.84 | 78b97e43d0b3 |
| 6.18 | 6.18.25 | 051e51aa55fd |
| 6.6 | 6.6.136 | b5c14bd4da1f |
| 7.0 | 7.0.2 | 50808c13452d |
| mainline | 7.1-rc1 | e76239fed3cf |