[PATCH] resolv: fix unaligned tmp buffer corner-case

Alexey Brodkin Alexey.Brodkin at synopsys.com
Wed Mar 11 23:21:12 UTC 2015

On execution of "inet/gethost_r-align" test I noticed failure due
to unaligned access (instaed of 4-byte aligned 1-byte aligned
address was attempted to be accessed).

Further investigation confirmed this nice and helpful test failure.
Following commit removed usage of ALIGN_BUFFER_OFFSET on entry to

So indeed if target architecture doesn't allow unaligned access
and provided tmp buffer is not word aligned (and we will deal with pointers
which means word-sized data units), then CPU will fail during execution.

In case of ARC we'll see "Unaligned access" exception like this:
 # potentially unexpected fatal signal 7.
 Path: /root/uClibc/test/inet/gethost_r-align
 CPU: 0 PID: 5514 Comm: gethost_r-align Not tainted 3.13.11 #2
 task: 8f42a580 ti: 8f40e000 task.ti: 8f40e000

 [ECR   ]: 0x00230400 => Misaligned r/w from 0x5fdab341
 [EFA   ]: 0x5fdab341
 [BLINK ]: 0x20032a18
 [ERET  ]: 0x20032a3c
     @off 0x12a3c in [/lib/libuClibc-0.9.34-git.so]
     VMA: 0x20020000 to 0x20062000
 [STAT32]: 0x00000086 : U         E2 E1
 BTA: 0x20046014  SP: 0x5fdab260  FP: 0x00000000
 LPS: 0x20046064 LPE: 0x20046068 LPC: 0x00000000
 r00: 0x5fdab341 r01: 0x00000005 r02: 0x00000015
 r03: 0x00000000 r04: 0x5fdab358 r05: 0x00000000
 r06: 0x0a0a0a00 r07: 0x00000000 r08: 0x0000003f
 r09: 0x20067050 r10: 0x00000000 r11: 0x00000014
 r12: 0x00000001 r13: 0x00000000 r14: 0x20060660
 r15: 0x20060661 r16: 0x00000006 r17: 0x5fdab371
 r18: 0x00000018 r19: 0x5fdab2b4 r20: 0x00020000
 r21: 0x00000000 r22: 0x00029068 r23: 0x5fdab371
 r24: 0x00010000 r25: 0x00000000

To fix this problem we'll re-introduce tmp buffer force alignment
before config parser invocation.

Signed-off-by: Alexey Brodkin <abrodkin at synopsys.com>
Cc: Vineet Gupta <vgupta at synopsys.com>
Cc: Waldemar Brodkorb <wbx at openadk.org>
 libc/inet/resolv.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/libc/inet/resolv.c b/libc/inet/resolv.c
index cfc1eee..7c678ce 100644
--- a/libc/inet/resolv.c
+++ b/libc/inet/resolv.c
@@ -1614,7 +1614,7 @@ int __read_etc_hosts_r(
 							sizeof(struct in_addr)
-	int ret = HOST_NOT_FOUND;
+	int i, ret = HOST_NOT_FOUND;
 	*h_errnop = NETDB_INTERNAL;
 	if (buflen < aliaslen
@@ -1626,6 +1626,12 @@ int __read_etc_hosts_r(
 		*result = NULL;
 		return errno;
+	/* make sure pointer is aligned */
+	buf += i;
+	buflen -= i;
 	/* Layout in buf:
 	 * char *alias[MAXTOKENS]  = {address, name, aliases...}
 	 * char **h_addr_list[1]   = {*in[6]_addr, NULL}

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