[PATCH] fix to oopsable race in binfmt_elf.c

[Alexander Viro]

	Changing current->fs requires task_lock(current) if old value
is non-NULL.  Otherwise we are risking oops on access to /proc/<pid>/{cwd,root}

diff -urN C2-pre3/fs/binfmt_elf.c C2-pre3-fs/fs/binfmt_elf.c
--- C2-pre3/fs/binfmt_elf.c	Sat Oct 20 22:16:59 2001
+++ C2-pre3-fs/fs/binfmt_elf.c	Sat Dec 29 15:14:18 2001
@@ -517,11 +517,13 @@
 				set_personality(PER_SVR4);
 				interpreter = open_exec(elf_interpreter);
 
+				task_lock(current);
 				new_domain = current->exec_domain;
 				new_fs = current->fs;
 				current->personality = old_pers;
 				current->exec_domain = old_domain;
 				current->fs = old_fs;
+				task_unlock(current);
 				put_exec_domain(new_domain);
 				put_fs_struct(new_fs);
 			} else