Fix a problem where zero-length RDATA fields can cause named(8) to crash.

[12:03]

Correct a privilege escalation when returning from kernel if
running FreeBSD/amd64 on non-AMD processors. [12:04]

Fix reference count errors in IPv6 code. [EN-12:02]

Security:	CVE-2012-1667
Security:	FreeBSD-SA-12:03.bind
Security:	CVE-2012-0217
Security:	FreeBSD-SA-12:04.sysret
Security:	FreeBSD-EN-12:02.ipv6refcount
Approved by:	so (simon, bz)

1 files changed, 17 insertions, 0 deletions

diff --git a/sys/amd64/amd64/trap.c b/sys/amd64/amd64/trap.c
index ffacb87..4216fd3 100644
--- a/sys/amd64/amd64/trap.c
+++ b/sys/amd64/amd64/trap.c
@@ -972,4 +972,21 @@ amd64_syscall(struct thread *td, int traced)
 	     syscallname(td->td_proc, sa.code)));
 
 	syscallret(td, error, &sa);
+
+	/*
+	 * If the user-supplied value of %rip is not a canonical
+	 * address, then some CPUs will trigger a ring 0 #GP during
+	 * the sysret instruction.  However, the fault handler would
+	 * execute with the user's %gs and %rsp in ring 0 which would
+	 * not be safe.  Instead, preemptively kill the thread with a
+	 * SIGBUS.
+	 */
+	if (td->td_frame->tf_rip >= VM_MAXUSER_ADDRESS) {
+		ksiginfo_init_trap(&ksi);
+		ksi.ksi_signo = SIGBUS;
+		ksi.ksi_code = BUS_OBJERR;
+		ksi.ksi_trapno = T_PROTFLT;
+		ksi.ksi_addr = (void *)td->td_frame->tf_rip;
+		trapsignal(td, &ksi);
+	}
 }