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Subject[PATCH 4.1 46/65] livepatch: add module locking around kallsyms calls
Date
4.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Miroslav Benes <mbenes@suse.cz>

commit 9a1bd63cdae4b623494c4ebaf723a91c35ec49fb upstream.

The list of loaded modules is walked through in
module_kallsyms_on_each_symbol (called by kallsyms_on_each_symbol). The
module_mutex lock should be acquired to prevent potential corruptions
in the list.

This was uncovered with new lockdep asserts in module code introduced by
the commit 0be964be0d45 ("module: Sanitize RCU usage and locking") in
recent next- trees.

Signed-off-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
kernel/livepatch/core.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)

--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -179,7 +179,9 @@ static int klp_find_object_symbol(const
.count = 0
};

+ mutex_lock(&module_mutex);
kallsyms_on_each_symbol(klp_find_callback, &args);
+ mutex_unlock(&module_mutex);

if (args.count == 0)
pr_err("symbol '%s' not found in symbol table\n", name);
@@ -219,13 +221,19 @@ static int klp_verify_vmlinux_symbol(con
.name = name,
.addr = addr,
};
+ int ret;

- if (kallsyms_on_each_symbol(klp_verify_callback, &args))
- return 0;
+ mutex_lock(&module_mutex);
+ ret = kallsyms_on_each_symbol(klp_verify_callback, &args);
+ mutex_unlock(&module_mutex);
+
+ if (!ret) {
+ pr_err("symbol '%s' not found at specified address 0x%016lx, kernel mismatch?\n",
+ name, addr);
+ return -EINVAL;
+ }

- pr_err("symbol '%s' not found at specified address 0x%016lx, kernel mismatch?\n",
- name, addr);
- return -EINVAL;
+ return 0;
}

static int klp_find_verify_func_addr(struct klp_object *obj,



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