---

yaml
---
r: 319875
b: refs/heads/master
c: 9520628
h: refs/heads/master
i:
  319873: fc7c92e
  319871: d1f6efd
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 779302e67835fe9a6b74327e54969ba59cb3478a
+refs/heads/master: 9520628e8ceb69fa9a4aee6b57f22675d9e1b709

trunk/Documentation/sysctl/fs.txt

@@ -163,16 +163,22 @@ This value can be used to query and set the core dump mode for setuid
 or otherwise protected/tainted binaries. The modes are
 
 0 - (default) - traditional behaviour. Any process which has changed
-	privilege levels or is execute only will not be dumped
+	privilege levels or is execute only will not be dumped.
 1 - (debug) - all processes dump core when possible. The core dump is
 	owned by the current user and no security is applied. This is
 	intended for system debugging situations only. Ptrace is unchecked.
+	This is insecure as it allows regular users to examine the memory
+	contents of privileged processes.
 2 - (suidsafe) - any binary which normally would not be dumped is dumped
-	readable by root only. This allows the end user to remove
-	such a dump but not access it directly. For security reasons
-	core dumps in this mode will not overwrite one another or
-	other files. This mode is appropriate when administrators are
-	attempting to debug problems in a normal environment.
+	anyway, but only if the "core_pattern" kernel sysctl is set to
+	either a pipe handler or a fully qualified path. (For more details
+	on this limitation, see CVE-2006-2451.) This mode is appropriate
+	when administrators are attempting to debug problems in a normal
+	environment, and either have a core dump pipe handler that knows
+	to treat privileged core dumps with care, or specific directory
+	defined for catching core dumps. If a core dump happens without
+	a pipe handler or fully qualifid path, a message will be emitted
+	to syslog warning about the lack of a correct setting.
 
 ==============================================================
 

trunk/fs/exec.c

@@ -2111,6 +2111,7 @@ void do_coredump(long signr, int exit_code, struct pt_regs *regs)
 	int retval = 0;
 	int flag = 0;
 	int ispipe;
+	bool need_nonrelative = false;
 	static atomic_t core_dump_count = ATOMIC_INIT(0);
 	struct coredump_params cprm = {
 		.signr = signr,
@@ -2136,14 +2137,16 @@ void do_coredump(long signr, int exit_code, struct pt_regs *regs)
 	if (!cred)
 		goto fail;
 	/*
-	 *	We cannot trust fsuid as being the "true" uid of the
-	 *	process nor do we know its entire history. We only know it
-	 *	was tainted so we dump it as root in mode 2.
+	 * We cannot trust fsuid as being the "true" uid of the process
+	 * nor do we know its entire history. We only know it was tainted
+	 * so we dump it as root in mode 2, and only into a controlled
+	 * environment (pipe handler or fully qualified path).
 	 */
 	if (__get_dumpable(cprm.mm_flags) == 2) {
 		/* Setuid core dump mode */
 		flag = O_EXCL;		/* Stop rewrite attacks */
 		cred->fsuid = GLOBAL_ROOT_UID;	/* Dump root private */
+		need_nonrelative = true;
 	}
 
 	retval = coredump_wait(exit_code, &core_state);
@@ -2223,6 +2226,14 @@ void do_coredump(long signr, int exit_code, struct pt_regs *regs)
 		if (cprm.limit < binfmt->min_coredump)
 			goto fail_unlock;
 
+		if (need_nonrelative && cn.corename[0] != '/') {
+			printk(KERN_WARNING "Pid %d(%s) can only dump core "\
+				"to fully qualified path!\n",
+				task_tgid_vnr(current), current->comm);
+			printk(KERN_WARNING "Skipping core dump\n");
+			goto fail_unlock;
+		}
+
 		cprm.file = filp_open(cn.corename,
 				 O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
 				 0600);