** Description changed:
- Upstream's Spectre v1 mitigation prevents speculation on a user
- controlled pointer. This part of the Spectre v1 patchset was never
- backported to 4.4 (for unknown reasons) so Xenial is lacking it as well.
- All the other stable upstream kernels include it, so add it to Xenial.
- Specifically, the following patches are needed:
+ == SRU Justification ==
+ Upstream's Spectre v1 mitigation prevents speculation on a user controlled
pointer. This part of the Spectre v1 patchset was never backported to 4.4 (for
unknown reasons) so Xenial/Trusty/Precise are lacking it as well. All the other
stable upstream kernels include it, so add it to our older kernels.
- c7f631cb07e7 x86/get_user: Use pointer masking to limit speculation
- 304ec1b05031 x86/uaccess: Use __uaccess_begin_nospec() and uaccess_try_nospec
- b5c4ae4f3532 x86/usercopy: Replace open coded stac/clac with
__uaccess_{begin, end}
- b3bbfb3fb5d2 x86: Introduce __uaccess_begin_nospec() and uaccess_try_nospec
+ == Fix ==
+ Backport the following patches:
+ x86/uaccess: Use __uaccess_begin_nospec() and uaccess_try_nospec
+ x86/usercopy: Replace open coded stac/clac with __uaccess_{begin, end}
+ x86: Introduce __uaccess_begin_nospec() and uaccess_try_nospec
+
+ == Regression Potential ==
+ Low. Patches have been in upstream (and other distro kernels) for quite a
while now and the changes only introduce a barrier on copy_from_user operations.
+
+ == Test Case ==
+ TBD.
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https://bugs.launchpad.net/bugs/1775137
Title:
Prevent speculation on user controlled pointer
Status in linux package in Ubuntu:
Incomplete
Bug description:
== SRU Justification ==
Upstream's Spectre v1 mitigation prevents speculation on a user controlled
pointer. This part of the Spectre v1 patchset was never backported to 4.4 (for
unknown reasons) so Xenial/Trusty/Precise are lacking it as well. All the other
stable upstream kernels include it, so add it to our older kernels.
== Fix ==
Backport the following patches:
x86/uaccess: Use __uaccess_begin_nospec() and uaccess_try_nospec
x86/usercopy: Replace open coded stac/clac with __uaccess_{begin, end}
x86: Introduce __uaccess_begin_nospec() and uaccess_try_nospec
== Regression Potential ==
Low. Patches have been in upstream (and other distro kernels) for quite a
while now and the changes only introduce a barrier on copy_from_user operations.
== Test Case ==
TBD.
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