Nikolai started to use shadow variables and found that list_head
is not initialized correctly using the existing API.
The problem is that LIST_HEAD_INIT() set pointers to itself.
klp_shadow_alloc() then copies these pointers to another location.
It would be possible to solve this by a late initialization. But
this does not work well with klp_shadow_get_or_alloc(). Also this
behavior is error prone. Note that list_head might be hidden in
another structure, for example mutex.
I suggest to change the API and allow to initialize the shadow
variables using a custom callback. I think that we have already
talked about this but we decided to go the easier way. It seems
that it was a bad decision.
I send also patch that add a symmetric callback to the klp_shadow_free()
functions. It might be handy especially for klp_shadow_free_all().
Changes against v2:
+ Use pr_err() instead of WARN() when ctor() fails [Josh]
+ Some typos [Mirek]
Changes against v1:
+ Rename init/free callbacks to ctor/dtor
+ Misc update of comments and commit messages
+ Fix sizeof() in the sample code in shadow-vars.txt
Petr Mladek (2):
livepatch: Initialize shadow variables safely by a custom callback
livepatch: Allow to call a custom callback when freeing shadow
variables
Documentation/livepatch/shadow-vars.txt | 41 ++++++++----
include/linux/livepatch.h | 19 ++++--
kernel/livepatch/shadow.c | 108 ++++++++++++++++++++----------
samples/livepatch/livepatch-shadow-fix1.c | 43 +++++++++---
samples/livepatch/livepatch-shadow-fix2.c | 33 ++++-----
5 files changed, 163 insertions(+), 81 deletions(-)
--
2.13.6
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