In the Linux kernel, the following vulnerability has been resolved:
x86: fix user address masking non-canonical speculation issue
It turns out that AMD has a "Meltdown Lite(tm)" issue with non-canonical
accesses in kernel space. And so using just the high bit to decide
whether an access is in user space or kernel space ends up with the good
old "leak speculative data" if you have the right gadget using the
result:
CVE-2020-12965 “Transient Execution of Non-Canonical Accesses“
Now, the kernel surrounds the access with a STAC/CLAC pair, and those
instructions end up serializing execution on older Zen architectures,
which closes the speculation window.
But that was true only up until Zen 5, which renames the AC bit [1].
That improves performance of STAC/CLAC a lot, but also means that the
speculation window is now open.
Note that this affects not just the new address masking, but also the
regular valid_user_address() check used by access_ok(), and the asm
version of the sign bit check in the get_user() helpers.
It does not affect put_user() or clear_user() variants, since there's no
speculative result to be used in a gadget for those operations.
Metrics
Affected Vendors & Products
References
History
Tue, 12 Nov 2024 15:30:00 +0000
Type | Values Removed | Values Added |
---|---|---|
First Time appeared |
Linux
Linux linux Kernel |
|
Weaknesses | CWE-203 | |
CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.12:rc1:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.12:rc2:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.12:rc3:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.12:rc4:*:*:*:*:*:* |
|
Vendors & Products |
Linux
Linux linux Kernel |
|
Metrics |
cvssV3_1
|
cvssV3_1
|
Wed, 06 Nov 2024 13:45:00 +0000
Type | Values Removed | Values Added |
---|---|---|
References |
| |
Metrics |
threat_severity
|
cvssV3_1
|
Tue, 05 Nov 2024 17:30:00 +0000
Type | Values Removed | Values Added |
---|---|---|
Description | In the Linux kernel, the following vulnerability has been resolved: x86: fix user address masking non-canonical speculation issue It turns out that AMD has a "Meltdown Lite(tm)" issue with non-canonical accesses in kernel space. And so using just the high bit to decide whether an access is in user space or kernel space ends up with the good old "leak speculative data" if you have the right gadget using the result: CVE-2020-12965 “Transient Execution of Non-Canonical Accesses“ Now, the kernel surrounds the access with a STAC/CLAC pair, and those instructions end up serializing execution on older Zen architectures, which closes the speculation window. But that was true only up until Zen 5, which renames the AC bit [1]. That improves performance of STAC/CLAC a lot, but also means that the speculation window is now open. Note that this affects not just the new address masking, but also the regular valid_user_address() check used by access_ok(), and the asm version of the sign bit check in the get_user() helpers. It does not affect put_user() or clear_user() variants, since there's no speculative result to be used in a gadget for those operations. | |
Title | x86: fix user address masking non-canonical speculation issue | |
References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published: 2024-11-05T17:10:37.986Z
Updated: 2024-12-19T09:33:08.192Z
Reserved: 2024-10-21T19:36:19.946Z
Link: CVE-2024-50102
Vulnrichment
No data.
NVD
Status : Analyzed
Published: 2024-11-05T18:15:13.877
Modified: 2024-11-12T15:08:00.563
Link: CVE-2024-50102
Redhat