Re: [PATCH] livepatch: Fix leak on klp_init_patch_early failure path

Josh Poimboeuf [off-list ref] wrote on Mon [2021-Dec-13 12:10:22 -0800]:

The patch description needs a few tweaks.  In the kernel we don't use
Markdown for patch descriptions.

A function can be postfixed with a trailing pair of parentheses, like
klp_enable_patch().

Other symbols can be enclosed with single quotes, like 'struct
klp_object'.

I'd also recommend avoiding the excessive use of "we", in favor of more
imperative-type language.

See Documentation/process/submitting-patches.rst for more details.  It's
also a good idea to look at some kernel commit logs to get a general
idea of the kernel patch description style.

Understood, I'll take a read through and re-submit the patch to honor the
norms for Linux kernel patches. My sincere apologies for the noise, and
thank you for the positive and constructive suggestions.

I don't think the fix will be quite that simple.  For example, if
klp_init_patch_early() fails, that means try_module_get() hasn't been
done, so klp_free_patch_finish() will wrongly do a module_put().

Ugh, good point and thank you for catching that. Another problem with the
current patch is that we'll call kobject_put() on the patch even if we
never call kobject_init on the patch due to patch->objs being NULL.

Perhaps we should pull try_module_get() and the NULL check for patch->objs
out of klp_init_patch_early()? It feels a bit more intuitive to me if
klp_init_patch_early() were only be responsible for initializing kobjects
for the patch and its objects / funcs anyways.

Testing it locally seems to work fine. Let me know if this sounds
reasonable to you, and I'll send out a v2 patch with the fixes to both the
patch description, and logic.

- David