[PATCH] Reset current->pdeath_signal on SUID binary execution (CVE-2007-3848)

This fixes a vulnerability in the "parent process death signal"
implementation discoverd by Wojciech Purczynski of COSEINC PTE Ltd.
and iSEC Security Research.

http://marc.info/?l=bugtraq&m=118711306802632&w=2Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Willy Tarreau <w@1wt.eu>

fs/exec.c

@@ -881,9 +881,12 @@ int flush_old_exec(struct linux_binprm * bprm)
 	 */
 	current->mm->task_size = TASK_SIZE;
 
-	if (bprm->e_uid != current->euid || bprm->e_gid != current->egid || 
-	    file_permission(bprm->file, MAY_READ) ||
-	    (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)) {
+	if (bprm->e_uid != current->euid || bprm->e_gid != current->egid) {
+		suid_keys(current);
+		current->mm->dumpable = suid_dumpable;
+		current->pdeath_signal = 0;
+	} else if (file_permission(bprm->file, MAY_READ) ||
+			(bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)) {
 		suid_keys(current);
 		current->mm->dumpable = suid_dumpable;
 	}
@@ -974,8 +977,10 @@ void compute_creds(struct linux_binprm *bprm)
 {
 	int unsafe;
 
-	if (bprm->e_uid != current->uid)
+	if (bprm->e_uid != current->uid) {
 		suid_keys(current);
+		current->pdeath_signal = 0;
+	}
 	exec_keys(current);
 
 	task_lock(current);