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fs: nfsd: Fix signedness bug in compare_blob

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Bugs similar to the one in acbbe6fbb2 (kcmp: fix standard comparison
bug) are in rich supply.

In this variant, the problem is that struct xdr_netobj::len has type
unsigned int, so the expression o1->len - o2->len _also_ has type
unsigned int; it has completely well-defined semantics, and the result
is some non-negative integer, which is always representable in a long
long. But this means that if the conditional triggers, we are
guaranteed to return a positive value from compare_blob.

In this case it could be fixed by

-       res = o1->len - o2->len;
+       res = (long long)o1->len - (long long)o2->len;

but I'd rather eliminate the usually broken 'return a - b;' idiom.

Reviewed-by: Jeff Layton <jlayton@primarydata.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
Rasmus Villemoes 2014-12-05 16:40:07 +01:00 committed by J. Bruce Fields
parent 83a712e0af
commit ef17af2a81
1 changed files with 7 additions and 8 deletions
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15
fs/nfsd/nfs4state.c
View file

@ -1714,15 +1714,14 @@ static int copy_cred(struct svc_cred *target, struct svc_cred *source)
return 0;
}
static long long
static int
compare_blob(const struct xdr_netobj *o1, const struct xdr_netobj *o2)
{
long long res;
res = o1->len - o2->len;
if (res)
return res;
return (long long)memcmp(o1->data, o2->data, o1->len);
if (o1->len < o2->len)
return -1;
if (o1->len > o2->len)
return 1;
return memcmp(o1->data, o2->data, o1->len);
}
static int same_name(const char *n1, const char *n2)
@ -1910,7 +1909,7 @@ add_clp_to_name_tree(struct nfs4_client *new_clp, struct rb_root *root)
static struct nfs4_client *
find_clp_in_name_tree(struct xdr_netobj *name, struct rb_root *root)
{
long long cmp;
int cmp;
struct rb_node *node = root->rb_node;
struct nfs4_client *clp;