Messages in this thread | | | From | Petr Mladek <> | Subject | [PATCH 0/2] livepatch: Allocate and free shadow variables more safely | Date | Tue, 13 Mar 2018 16:54:46 +0100 |
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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().
The patchset is against the current Linus' tree.
Petr Mladek (2): livepatch: Initialize shadow variables by init function safely livepatch: Allow to unregister or free shadow data using a custom function
Documentation/livepatch/shadow-vars.txt | 42 ++++++++++++----- include/linux/livepatch.h | 23 +++++++--- kernel/livepatch/shadow.c | 75 +++++++++++++++++++++---------- samples/livepatch/livepatch-shadow-fix1.c | 44 +++++++++++++----- samples/livepatch/livepatch-shadow-fix2.c | 33 +++++++------- 5 files changed, 150 insertions(+), 67 deletions(-)
-- 2.13.6
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