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Create verifier used by FreeBSD NFS client is suboptimal because the

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first part of a verifier is set to the first IP address from
V_in_ifaddrhead list. This address is typically the loopback address
making the first part of the verifier practically non-unique. The second
part of the verifier is initialized to zero making its initial value
non-unique too.

This commit changes the strategy for create verifier initialization:
just initialize it to a random value. Also move verifier handling into
its own function and use a mutex to protect the variable.

This change is a candidate for porting to sys/nfsclient.

Reviewed by:	jhb, rmacklem
Approved by:	trasz (mentor)
This commit is contained in:
Jaakko Heinonen 2009-11-11 15:43:07 +00:00
parent a087c7295d
commit 1bb015c07c
1 changed files with 25 additions and 14 deletions
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39
sys/fs/nfsclient/nfs_clvnops.c
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@ -1365,7 +1365,30 @@ nfs_mknod(struct vop_mknod_args *ap)
return (nfs_mknodrpc(ap->a_dvp, ap->a_vpp, ap->a_cnp, ap->a_vap));
}
static u_long create_verf;
static struct mtx nfs_cverf_mtx;
MTX_SYSINIT(nfs_cverf_mtx, &nfs_cverf_mtx, "NFS create verifier mutex",
MTX_DEF);
static nfsquad_t
nfs_get_cverf(void)
{
static nfsquad_t cverf;
nfsquad_t ret;
static int cverf_initialized = 0;
mtx_lock(&nfs_cverf_mtx);
if (cverf_initialized == 0) {
cverf.lval[0] = arc4random();
cverf.lval[1] = arc4random();
cverf_initialized = 1;
} else
cverf.qval++;
ret = cverf;
mtx_unlock(&nfs_cverf_mtx);
return (ret);
}
/*
* nfs file create call
*/
@ -1405,19 +1428,7 @@ again:
}
mtx_unlock(&dnp->n_mtx);
#ifdef INET
CURVNET_SET(CRED_TO_VNET(cnp->cn_cred));
IN_IFADDR_RLOCK();
if (!TAILQ_EMPTY(&V_in_ifaddrhead))
cverf.lval[0] = IA_SIN(TAILQ_FIRST(&V_in_ifaddrhead))->sin_addr.s_addr;
else
#endif
cverf.lval[0] = create_verf;
#ifdef INET
IN_IFADDR_RUNLOCK();
CURVNET_RESTORE();
#endif
cverf.lval[1] = ++create_verf;
cverf = nfs_get_cverf();
error = nfsrpc_create(dvp, cnp->cn_nameptr, cnp->cn_namelen,
vap, cverf, fmode, cnp->cn_cred, cnp->cn_thread, &dnfsva, &nfsva,
&nfhp, &attrflag, &dattrflag, NULL);