kobject_uevent: Fix OOB access within zap_modalias_env()
commit dd6e9894b451e7c85cceb8e9dc5432679a70e7dc upstream.
zap_modalias_env() wrongly calculates size of memory block to move, so
will cause OOB memory access issue if variable MODALIAS is not the last
one within its @env parameter, fixed by correcting size to memmove.
Fixes: 9b3fa47d4a76 ("kobject: fix suppressing modalias in uevents delivered over netlink")
Cc: [email protected]
Signed-off-by: Zijun Hu <[email protected]>
Reviewed-by: Lk Sii <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
index 7c44b7a..d397b1a 100644
--- a/lib/kobject_uevent.c
+++ b/lib/kobject_uevent.c
@@ -432,8 +432,23 @@ static void zap_modalias_env(struct kobj_uevent_env *env)
len = strlen(env->envp[i]) + 1;
if (i != env->envp_idx - 1) {
+ /* @env->envp[] contains pointers to @env->buf[]
+ * with @env->buflen chars, and we are removing
+ * variable MODALIAS here pointed by @env->envp[i]
+ * with length @len as shown below:
+ *
+ * 0 @env->buf[] @env->buflen
+ * ---------------------------------------------
+ * ^ ^ ^ ^
+ * | |-> @len <-| target block |
+ * @env->envp[0] @env->envp[i] @env->envp[i + 1]
+ *
+ * so the "target block" indicated above is moved
+ * backward by @len, and its right size is
+ * @env->buflen - (@env->envp[i + 1] - @env->envp[0]).
+ */
memmove(env->envp[i], env->envp[i + 1],
- env->buflen - len);
+ env->buflen - (env->envp[i + 1] - env->envp[0]));
for (j = i; j < env->envp_idx - 1; j++)
env->envp[j] = env->envp[j + 1] - len;
