CVE-2015-1781: resolv/nss_dns/dns-host.c buffer overflow [BZ#18287]

diff --git a/ChangeLog b/ChangeLog
index 7c3e625..26dcfc7 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2015-04-21  Arjun Shankar  <arjun.is@lostca.se>
+
+       [BZ #18287]
+       * resolv/nss_dns/dns-host.c (getanswer_r): Adjust buffer length
+       based on padding.  (CVE-2015-1781)
+
 2015-04-20  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
 
        * nptl/pthread_cond_timedwait.c: Change include bits/libc-vdso.h to just

diff --git a/NEWS b/NEWS
index 2bbd6a3..ccc4d13 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -16,7 +16,14 @@ Version 2.22
   17969, 17978, 17987, 17991, 17996, 17998, 17999, 18019, 18020, 18029,
   18030, 18032, 18036, 18038, 18039, 18042, 18043, 18046, 18047, 18068,
   18080, 18093, 18100, 18104, 18110, 18111, 18128, 18138, 18185, 18197,
-  18206, 18210, 18211, 18247.
+  18206, 18210, 18211, 18247, 18287.
+
+* A buffer overflow in gethostbyname_r and related functions performing DNS
+  requests has been fixed.  If the NSS functions were called with a
+  misaligned buffer, the buffer length change due to pointer alignment was
+  not taken into account.  This could result in application crashes or,
+  potentially arbitrary code execution, using crafted, but syntactically
+  valid DNS responses.  (CVE-2015-1781)
 
 * A powerpc and powerpc64 optimization for TLS, similar to TLS descriptors
   for LD and GD on x86 and x86-64, has been implemented.  You will need

diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c
index b16b0dd..d8c5579 100644 (file)
--- a/resolv/nss_dns/dns-host.c
+++ b/resolv/nss_dns/dns-host.c
@@ -615,7 +615,8 @@ getanswer_r (const querybuf *answer, int anslen, const char *qname, int qtype,
   int have_to_map = 0;
   uintptr_t pad = -(uintptr_t) buffer % __alignof__ (struct host_data);
   buffer += pad;
-  if (__glibc_unlikely (buflen < sizeof (struct host_data) + pad))
+  buflen = buflen > pad ? buflen - pad : 0;
+  if (__glibc_unlikely (buflen < sizeof (struct host_data)))
     {
       /* The buffer is too small.  */
     too_small: