CVE-2021-47227

published 2024-05-21

CVE-2021-47227: In the Linux kernel, the following vulnerability has been resolved: x86/fpu: Prevent state corruption in __fpu__restore_sig() The non-compacted slowpath uses…

Priority P4 22 medium 5.5 CVSS 3.1

AV L AC L PR L UI N S U C N I N A H

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

x86/fpu: Prevent state corruption in __fpu__restore_sig()

The non-compacted slowpath uses __copy_from_user() and copies the entire
user buffer into the kernel buffer, verbatim. This means that the kernel
buffer may now contain entirely invalid state on which XRSTOR will #GP.
validate_user_xstate_header() can detect some of that corruption, but that
leaves the onus on callers to clear the buffer.

Prior to XSAVES support, it was possible just to reinitialize the buffer,
completely, but with supervisor states that is not longer possible as the
buffer clearing code split got it backwards. Fixing that is possible but
not corrupting the state in the first place is more robust.

Avoid corruption of the kernel XSAVE buffer by using copy_user_to_xstate()
which validates the XSAVE header contents before copying the actual states
to the kernel. copy_user_to_xstate() was previously only called for
compacted-format kernel buffers, but it works for both compacted and
non-compacted forms.

Using it for the non-compacted form is slower because of multiple
__copy_from_user() operations, but that cost is less important than robust
code in an already slow path.

[ Changelog polished by Dave Hansen ]

Affected

12 ranges

Vendor	Product	Version range	Fixed in
debian	linux	< linux 5.10.46-1 (bookworm)	linux 5.10.46-1 (bookworm)
linux	linux	—	—
linux	linux	>= b860eb8dce5906b14e3a7f3c771e0b3d6ef61b94 < 076f732b16a5bf842686e1b43ab6021a2d98233e	076f732b16a5bf842686e1b43ab6021a2d98233e
linux	linux	>= b860eb8dce5906b14e3a7f3c771e0b3d6ef61b94 < ec25ea1f3f05d6f8ee51d1277efea986eafd4f2a	ec25ea1f3f05d6f8ee51d1277efea986eafd4f2a
linux	linux	>= b860eb8dce5906b14e3a7f3c771e0b3d6ef61b94 < 484cea4f362e1eeb5c869abbfb5f90eae6421b38	484cea4f362e1eeb5c869abbfb5f90eae6421b38
linux	linux_kernel	—	—
linux	linux_kernel	>= 0 < 5.10.46-1	5.10.46-1
linux	linux_kernel	>= 0 < 5.10.46-1	5.10.46-1
linux	linux_kernel	>= 0 < 5.10.46-1	5.10.46-1
linux	linux_kernel	>= 0 < 5.10.46-1	5.10.46-1
linux	linux_kernel	>= 5.11 < 5.12.13	5.12.13
linux	linux_kernel	>= 5.8 < 5.10.46	5.10.46

CVSS provenance

nvd v3.1 5.5 MEDIUM CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

osv 5.5 MEDIUM

vendor_debian 5.5 MEDIUM

vendor_redhat 5.5 MEDIUM

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