From e0523d622cdf5b96575ce025221ec2533a6b4454 Mon Sep 17 00:00:00 2001
From: Mike Frysinger <vapier@gentoo.org>
Date: Wed, 9 Jan 2008 05:49:44 +0000
Subject: Daniel Jacobowitz writes: MontaVista noticed that when their kernels
were configured to trap on unaligned access gethostbyname_r could
mysteriously crash. I tracked this down to an unaligned buffer being passed
to gethostbyname_r from some other part of uClibc (afraid I don't remember
where from any more). We have to pad the beginning of the buffer to a
pointer alignment before we store pointers in it.
---
libc/inet/resolv.c | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
(limited to 'libc/inet')
diff --git a/libc/inet/resolv.c b/libc/inet/resolv.c
index 7f9d7d536..591106a24 100644
--- a/libc/inet/resolv.c
+++ b/libc/inet/resolv.c
@@ -234,6 +234,14 @@ libc_hidden_proto(__ctype_b)
#define DPRINTF(X,args...)
#endif /* DEBUG */
+/* Make sure the incoming char * buffer is aligned enough to handle our random
+ * structures. This define is the same as we use for malloc alignment (which
+ * has same requirements). The offset is the number of bytes we need to adjust
+ * in order to attain desired alignment.
+ */
+#define ALIGN_ATTR __alignof__(double __attribute_aligned__ (sizeof(size_t)))
+#define ALIGN_BUFFER_OFFSET(buf) ((ALIGN_ATTR - ((size_t)buf % ALIGN_ATTR)) % ALIGN_ATTR)
+
/* Global stuff (stuff needing to be locked to be thread safe)... */
extern int __nameservers attribute_hidden;
@@ -1534,6 +1542,15 @@ int attribute_hidden __read_etc_hosts_r(FILE * fp, const char * name, int type,
char *cp, **alias;
int aliases, i, ret = HOST_NOT_FOUND;
+ /* make sure user char * is aligned */
+ i = ALIGN_BUFFER_OFFSET(buf);
+ if (unlikely(i)) {
+ if (buflen < i)
+ return ERANGE;
+ buf += i;
+ buflen -= i;
+ }
+
if (buflen < sizeof(char *)*(ALIAS_DIM))
return ERANGE;
alias = (char **)buf;
@@ -2029,6 +2046,15 @@ int gethostbyname_r(const char * name,
DPRINTF("Nothing found in /etc/hosts\n");
+ /* make sure user char * is aligned */
+ i = ALIGN_BUFFER_OFFSET(buf);
+ if (unlikely(i)) {
+ if (buflen < i)
+ return ERANGE;
+ buf += i;
+ buflen -= i;
+ }
+
*h_errnop = NETDB_INTERNAL;
if (buflen < sizeof(*in))
return ERANGE;
--
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