[PATCH v6 kspp-next 16/22] livepatch: only match unique symbols when using fgkaslr

Alexander Lobakin
2021-08-31T14:42:53Z

From: Kristen Carlson Accardi <kristen@linux.intel.com>

If any type of function granular randomization is enabled, the sympos
algorithm will fail, as it will be impossible to resolve symbols when
there are duplicates using the previous symbol position.

Override the value of sympos to always be zero if fgkaslr is enabled for
either the core kernel or modules, forcing the algorithm
to require that only unique symbols are allowed to be patched.

Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>
---
kernel/livepatch/core.c | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 335d988bd811..852bbfa9da7b 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -169,6 +169,17 @@ static int klp_find_object_symbol(const char *objname, const char *name,
else
kallsyms_on_each_symbol(klp_find_callback, &args);

+ /*
+ * If any type of function granular randomization is enabled, it
+ * will be impossible to resolve symbols when there are duplicates
+ * using the previous symbol position (i.e. sympos != 0). Override
+ * the value of sympos to always be zero in this case. This will
+ * force the algorithm to require that only unique symbols are
+ * allowed to be patched.
+ */
+ if (IS_ENABLED(CONFIG_FG_KASLR))
+ sympos = 0;
+
/*
* Ensure an address was found. If sympos is 0, ensure symbol is unique;
* otherwise ensure the symbol position count matches sympos.
--
2.31.1