[Bug 2003374] Re: Undefined Behavior Sanitizer (UBSAN) causes failure to match symbols

** Changed in: dh-kpatches
Status: Unknown => Fix Released

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https://bugs.launchpad.net/bugs/2003374

Title:
Undefined Behavior Sanitizer (UBSAN) causes failure to match symbols

Status in dh-kpatches:
Fix Released
Status in Ubuntu on IBM z Systems:
Fix Committed
Status in kpatch package in Ubuntu:
In Progress
Status in linux package in Ubuntu:
Fix Released
Status in kpatch source package in Jammy:
In Progress
Status in linux source package in Jammy:
Fix Released
Status in kpatch source package in Kinetic:
Won't Fix

Bug description:
[ Impact ]

 * When UBSAN is enabled in an s390x kernel configuration, kpatch-
build can fail to find matching symbols in the vmlinux symbol table
(see attached example_livepatch.patch). This was discovered in both
Jammy 5.15 and Kinetic 5.19 kernels, where UBSAN was first enabled
(releases up to Focal did not enable UBSAN). See attached kpatch-build
console output (output.log) and kpatch-build log (build.log).

* Disabling UBSAN in s390x kernel configurations resolved the issue
for both Jammy 5.15 and Kinetic 5.19. Possibly this could be fixed in
kpatch/kpatch-build to continue to enable UBSAN while still allowing
Livepatch functionality.

[ Test Plan ]

 * Use kpatch-build testcases to build and load a fs/proc/meminfo.c
Livepatch on s390x kernel (see attached example_livepatch.patch). This
should be successful.

[ Where problems could occur ]

 * A fix in kpatch/kpatch-build to properly handle UBSAN objects
shouldn't yield any regressions. If UBSAN is disabled to ultimately
get past this issue, it could lead to undefined behavior not being
caught.

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