From 26349fcf80982b4d0120b73b2836e88bcf16853c Mon Sep 17 00:00:00 2001
|
From: Chris Coulson <chris.coulson@canonical.com>
|
Date: Fri, 10 Jul 2020 14:41:45 +0100
|
Subject: [PATCH] script: Avoid a use-after-free when redefining a
|
function during execution
|
MIME-Version: 1.0
|
Content-Type: text/plain; charset=UTF-8
|
Content-Transfer-Encoding: 8bit
|
|
Defining a new function with the same name as a previously defined
|
function causes the grub_script and associated resources for the
|
previous function to be freed. If the previous function is currently
|
executing when a function with the same name is defined, this results
|
in use-after-frees when processing subsequent commands in the original
|
function.
|
|
Instead, reject a new function definition if it has the same name as
|
a previously defined function, and that function is currently being
|
executed. Although a behavioural change, this should be backwards
|
compatible with existing configurations because they can't be
|
dependent on the current behaviour without being broken.
|
|
Fixes: CVE-2020-15706
|
|
Signed-off-by: Chris Coulson <chris.coulson@canonical.com>
|
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
|
Signed-off-by: Stefan Sørensen <stefan.sorensen@spectralink.com>
|
---
|
grub-core/script/execute.c | 2 ++
|
grub-core/script/function.c | 16 +++++++++++++---
|
grub-core/script/parser.y | 3 ++-
|
include/grub/script_sh.h | 2 ++
|
4 files changed, 19 insertions(+), 4 deletions(-)
|
|
diff --git a/grub-core/script/execute.c b/grub-core/script/execute.c
|
index c8d6806fe..7e028e135 100644
|
--- a/grub-core/script/execute.c
|
+++ b/grub-core/script/execute.c
|
@@ -838,7 +838,9 @@ grub_script_function_call (grub_script_function_t func, int argc, char **args)
|
old_scope = scope;
|
scope = &new_scope;
|
|
+ func->executing++;
|
ret = grub_script_execute (func->func);
|
+ func->executing--;
|
|
function_return = 0;
|
active_loops = loops;
|
diff --git a/grub-core/script/function.c b/grub-core/script/function.c
|
index d36655e51..3aad04bf9 100644
|
--- a/grub-core/script/function.c
|
+++ b/grub-core/script/function.c
|
@@ -34,6 +34,7 @@ grub_script_function_create (struct grub_script_arg *functionname_arg,
|
func = (grub_script_function_t) grub_malloc (sizeof (*func));
|
if (! func)
|
return 0;
|
+ func->executing = 0;
|
|
func->name = grub_strdup (functionname_arg->str);
|
if (! func->name)
|
@@ -60,10 +61,19 @@ grub_script_function_create (struct grub_script_arg *functionname_arg,
|
grub_script_function_t q;
|
|
q = *p;
|
- grub_script_free (q->func);
|
- q->func = cmd;
|
grub_free (func);
|
- func = q;
|
+ if (q->executing > 0)
|
+ {
|
+ grub_error (GRUB_ERR_BAD_ARGUMENT,
|
+ N_("attempt to redefine a function being executed"));
|
+ func = NULL;
|
+ }
|
+ else
|
+ {
|
+ grub_script_free (q->func);
|
+ q->func = cmd;
|
+ func = q;
|
+ }
|
}
|
else
|
{
|
diff --git a/grub-core/script/parser.y b/grub-core/script/parser.y
|
index 4f0ab8319..f80b86b6f 100644
|
--- a/grub-core/script/parser.y
|
+++ b/grub-core/script/parser.y
|
@@ -289,7 +289,8 @@ function: "function" "name"
|
grub_script_mem_free (state->func_mem);
|
else {
|
script->children = state->scripts;
|
- grub_script_function_create ($2, script);
|
+ if (!grub_script_function_create ($2, script))
|
+ grub_script_free (script);
|
}
|
|
state->scripts = $<scripts>3;
|
diff --git a/include/grub/script_sh.h b/include/grub/script_sh.h
|
index b382bcf09..6c48e0751 100644
|
--- a/include/grub/script_sh.h
|
+++ b/include/grub/script_sh.h
|
@@ -361,6 +361,8 @@ struct grub_script_function
|
|
/* The next element. */
|
struct grub_script_function *next;
|
+
|
+ unsigned executing;
|
};
|
typedef struct grub_script_function *grub_script_function_t;
|
|
--
|
2.26.2
|
