Public bug reported:
[Impact]
In order to support Rust in the kernel starting with Lunar we had to
apply the following UBUNTU SAUCE patch:
27c4fe11712c ("UBUNTU: SAUCE: modpost: support arbitrary symbol length
in modversion")
This patch can potentially introduce a user-space regression, because it alters
how the module names are stored in the modversion_info area. Realistically it
doesn't break anything, since this area is used only by the kmod tools (and
they've been verified to work fine also with this change applied).
However, to be 100% that we don't introduce regressions it is safer to
simply revert this patch, considering that we don't provide kernel Rust
support in Jammy and without Rust this patch doesn't provide any
benefit.
[Fix]
In order to fix this we need to explicitly revert the patch in all the
Jammy kernels that are derived from any Lunar kernel.
To do so, after `cranky rebase`, run:
git revert -s 27c4fe11712c
The comment for the revert should report something like this:
```
Revert "UBUNTU: SAUCE: modpost: support arbitrary symbol length in
modversion"
This patch is required by Rust and it can potentially break user-space.
It is safer to revert this in all the kernel backported to old releases.
```
[Regression potential]
This revert is not very critical, realistically even with the variable
modversions patch applied we won't regress any known tool, however we
don't to risk to introduce potential user-space ABI changes. Fixing this
requires a slightly different action, respect to our usual workflow, so
if some kernels are shipped with the variable modversion patch (for any
reason), we may experience regressions with kmod-related tools (e.g.,
scripts that are using modinfo, modprobe and similar or custom tools
that are parsing .ko sections directly).
** Affects: linux-hwe-6.2 (Ubuntu)
Importance: Undecided
Status: Fix Committed
** Affects: linux-lowlatency-hwe-6.2 (Ubuntu)
Importance: Undecided
Status: Fix Committed
** Also affects: linux (Ubuntu Jammy)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2025134
Title:
Revert variable symbol length modversion in all the jammy kernels
Status in linux-hwe-6.2 package in Ubuntu:
Fix Committed
Status in linux-lowlatency-hwe-6.2 package in Ubuntu:
Fix Committed
Bug description:
[Impact]
In order to support Rust in the kernel starting with Lunar we had to
apply the following UBUNTU SAUCE patch:
27c4fe11712c ("UBUNTU: SAUCE: modpost: support arbitrary symbol
length in modversion")
This patch can potentially introduce a user-space regression, because it
alters how the module names are stored in the modversion_info area.
Realistically it doesn't break anything, since this area is used only by the
kmod tools (and they've been verified to work fine also with this change
applied).
However, to be 100% that we don't introduce regressions it is safer to
simply revert this patch, considering that we don't provide kernel
Rust support in Jammy and without Rust this patch doesn't provide any
benefit.
[Fix]
In order to fix this we need to explicitly revert the patch in all the
Jammy kernels that are derived from any Lunar kernel.
To do so, after `cranky rebase`, run:
git revert -s 27c4fe11712c
The comment for the revert should report something like this:
```
Revert "UBUNTU: SAUCE: modpost: support arbitrary symbol length in
modversion"
This patch is required by Rust and it can potentially break user-space.
It is safer to revert this in all the kernel backported to old releases.
```
[Regression potential]
This revert is not very critical, realistically even with the variable
modversions patch applied we won't regress any known tool, however we
don't to risk to introduce potential user-space ABI changes. Fixing
this requires a slightly different action, respect to our usual
workflow, so if some kernels are shipped with the variable modversion
patch (for any reason), we may experience regressions with kmod-
related tools (e.g., scripts that are using modinfo, modprobe and
similar or custom tools that are parsing .ko sections directly).
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux-hwe-6.2/+bug/2025134/+subscriptions
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