exportfs crash with long path

[Ivan Romanov <drizt@land.ru>]

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Hello. I opened a bug with nfs-utils on Redhat Bugzilla. And got an
advice to email upstream. So I just repeat my bug text with a patch.

How reproducible:
always

Steps to Reproduce:
# mkdir -p /home/kudinae/Общедоступные
# echo '/home/kudinae/Общедоступные oek-1(rw,sync,no_wdelay,no_root_squash,no_subtree_check)' > /etc/exports
# exportfs -a
Segmentation fault

I've obtained the sources. So a crush happens on export.c:293. variable
pos has negative value. I think problem into strtoint and export_hash
functions. strtoint has unsigned type and always returns positive value
but export_hash impicity cast it to signed int. So it is possible to
get negative value. I wrote patch to fix this.

Original Red Hat bug
https://bugzilla.redhat.com/show_bug.cgi?id=863054

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diff --git a/support/export/export.c b/support/export/export.c
index 4fda30a..0257903 100644
--- a/support/export/export.c
+++ b/support/export/export.c
@@ -357,7 +357,7 @@ strtoint(char *str)
 static int 
 export_hash(char *str)
 {
-	int num = strtoint(str);
+	unsigned int num = strtoint(str);
 
 	return num % HASH_TABLE_SIZE;
 }