Invalid return value of execve() resulting in oopses

From: Alexey Kuznetsov <[email protected]>

When elf loader fails to map executable (due to memory shortage or because binary is malformed), it can return 0. Normally, this is invisible because process is killed with SIGKILL and it never returns to user space.

But if exec() is called from kernel thread (hotplug, whatever) consequences are more interesting and vary depending on architecture.

i386. Nothing especially interesting, execve() just returns

        with "success"  :-)

x86_64. Fake zero frame is used on way to caller, RSP/RIP are loaded
with zeros, ergo... double fault.

ia64. Similar to i386, but r32...r95 are corrupted. Sometimes it
oopses due to return to zero PC, sometimes it sees NaT in rXX and oopses due to NaT consumption.

---

index 67d9b31..fa8ea33 100644
@@ -871,6 +871,8 @@ static int load_elf_binary(struct linux_
 				elf_prot, elf_flags);
 		if (BAD_ADDR(error)) {
 			send_sig(SIGKILL, current, 0);
+			retval = IS_ERR((void *)error) ?
+				PTR_ERR((void*)error) : -EINVAL;
 			goto out_free_dentry;
 		}
 

@@ -900,6 +902,7 @@ static int load_elf_binary(struct linux_
 		    TASK_SIZE - elf_ppnt->p_memsz < k) {
 			/* set_brk can never work. Avoid overflows. */
 			send_sig(SIGKILL, current, 0);
+			retval = -EINVAL;
 			goto out_free_dentry;
 		}