linux-kernel - [PATCH 4.18 078/145] livepatch: Validate module/old func name length

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Date:   Fri,  7 Sep 2018 23:09:04 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jiri Kosina <jkosina@...e.cz>
Subject: [PATCH 4.18 078/145] livepatch: Validate module/old func name length

4.18-stable review patch.  If anyone has any objections, please let me know.

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

From: Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>

commit 6e9df95b76cad18f7b217bdad7bb8a26d63b8c47 upstream.

livepatch module author can pass module name/old function name with more
than the defined character limit. With obj->name length greater than
MODULE_NAME_LEN, the livepatch module gets loaded but waits forever on
the module specified by obj->name to be loaded. It also populates a /sys
directory with an untruncated object name.

In the case of funcs->old_name length greater then KSYM_NAME_LEN, it
would not match against any of the symbol table entries. Instead loop
through the symbol table comparing them against a nonexisting function,
which can be avoided.

The same issues apply, to misspelled/incorrect names. At least gatekeep
the modules with over the limit string length, by checking for their
length during livepatch module registration.

Cc: stable@...r.kernel.org
Signed-off-by: Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>
Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>
Signed-off-by: Jiri Kosina <jkosina@...e.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/livepatch/core.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -678,6 +678,9 @@ static int klp_init_func(struct klp_obje
 	if (!func->old_name || !func->new_func)
 		return -EINVAL;

+	if (strlen(func->old_name) >= KSYM_NAME_LEN)
+		return -EINVAL;
+
 	INIT_LIST_HEAD(&func->stack_node);
 	func->patched = false;
 	func->transition = false;
@@ -751,6 +754,9 @@ static int klp_init_object(struct klp_pa
 	if (!obj->funcs)
 		return -EINVAL;

+	if (klp_is_module(obj) && strlen(obj->name) >= MODULE_NAME_LEN)
+		return -EINVAL;
+
 	obj->patched = false;
 	obj->mod = NULL;