From: Lidong Chen <lidong.c...@oracle.com>
The test_parse() evaluates test expression recursively. Due to lack of
recursion depth check a specially crafted expression may cause a stack
overflow. The recursion is only triggered by the parentheses usage and
it can be unlimited. However, sensible expressions are unlikely to
contain more than a few parentheses. So, this patch limits the recursion
depth to 100, which should be sufficient.
Reported-by: Nils Langius <n...@langius.de>
Signed-off-by: Lidong Chen <lidong.c...@oracle.com>
Reviewed-by: Daniel Kiper <daniel.ki...@oracle.com>
---
grub-core/commands/test.c | 21 ++++++++++++++++++---
1 file changed, 18 insertions(+), 3 deletions(-)
diff --git a/grub-core/commands/test.c b/grub-core/commands/test.c
index 62d3fb398..b585c3d70 100644
--- a/grub-core/commands/test.c
+++ b/grub-core/commands/test.c
@@ -29,6 +29,9 @@
GRUB_MOD_LICENSE ("GPLv3+");
+/* Set a limit on recursion to avoid stack overflow. */
+#define MAX_TEST_RECURSION_DEPTH 100
+
/* A simple implementation for signed numbers. */
static int
grub_strtosl (char *arg, const char ** const end, int base)
@@ -150,7 +153,7 @@ get_fileinfo (char *path, struct test_parse_ctx *ctx)
/* Parse a test expression starting from *argn. */
static int
-test_parse (char **args, int *argn, int argc)
+test_parse (char **args, int *argn, int argc, int *depth)
{
struct test_parse_ctx ctx = {
.and = 1,
@@ -387,13 +390,24 @@ test_parse (char **args, int *argn, int argc)
if (grub_strcmp (args[*argn], ")") == 0)
{
(*argn)++;
+ if (*depth > 0)
+ (*depth)--;
+
return ctx.or || ctx.and;
}
/* Recursively invoke if parenthesis. */
if (grub_strcmp (args[*argn], "(") == 0)
{
(*argn)++;
- update_val (test_parse (args, argn, argc), &ctx);
+
+ if (++(*depth) > MAX_TEST_RECURSION_DEPTH)
+ {
+ grub_error (GRUB_ERR_OUT_OF_RANGE, N_("max recursion depth
exceeded"));
+ depth--;
+ return ctx.or || ctx.and;
+ }
+
+ update_val (test_parse (args, argn, argc, depth), &ctx);
continue;
}
@@ -428,11 +442,12 @@ grub_cmd_test (grub_command_t cmd __attribute__
((unused)),
int argc, char **args)
{
int argn = 0;
+ int depth = 0;
if (argc >= 1 && grub_strcmp (args[argc - 1], "]") == 0)
argc--;
- return test_parse (args, &argn, argc) ? GRUB_ERR_NONE
+ return test_parse (args, &argn, argc, &depth) ? GRUB_ERR_NONE
: grub_error (GRUB_ERR_TEST_FAILURE, N_("false"));
}
--
2.11.0
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