From 016baaa1183bb0c5fb2a7de42413bba8a51c1bc8 Mon Sep 17 00:00:00 2001 From: Herbert Xu Date: Tue, 7 Apr 2015 21:27:01 +0800 Subject: crypto: user - Fix crypto_alg_match race The function crypto_alg_match returns an algorithm without taking any references on it. This means that the algorithm can be freed at any time, therefore all users of crypto_alg_match are buggy. This patch fixes this by taking a reference count on the algorithm to prevent such races. Signed-off-by: Herbert Xu --- crypto/crypto_user.c | 39 +++++++++++++++++++++++++++++---------- 1 file changed, 29 insertions(+), 10 deletions(-) (limited to 'crypto') diff --git a/crypto/crypto_user.c b/crypto/crypto_user.c index eab249723830..41dfe762b7fb 100644 --- a/crypto/crypto_user.c +++ b/crypto/crypto_user.c @@ -62,10 +62,14 @@ static struct crypto_alg *crypto_alg_match(struct crypto_user_alg *p, int exact) else if (!exact) match = !strcmp(q->cra_name, p->cru_name); - if (match) { - alg = q; - break; - } + if (!match) + continue; + + if (unlikely(!crypto_mod_get(q))) + continue; + + alg = q; + break; } up_read(&crypto_alg_sem); @@ -205,9 +209,10 @@ static int crypto_report(struct sk_buff *in_skb, struct nlmsghdr *in_nlh, if (!alg) return -ENOENT; + err = -ENOMEM; skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_ATOMIC); if (!skb) - return -ENOMEM; + goto drop_alg; info.in_skb = in_skb; info.out_skb = skb; @@ -215,6 +220,10 @@ static int crypto_report(struct sk_buff *in_skb, struct nlmsghdr *in_nlh, info.nlmsg_flags = 0; err = crypto_report_alg(alg, &info); + +drop_alg: + crypto_mod_put(alg); + if (err) return err; @@ -284,6 +293,7 @@ static int crypto_update_alg(struct sk_buff *skb, struct nlmsghdr *nlh, up_write(&crypto_alg_sem); + crypto_mod_put(alg); crypto_remove_final(&list); return 0; @@ -294,6 +304,7 @@ static int crypto_del_alg(struct sk_buff *skb, struct nlmsghdr *nlh, { struct crypto_alg *alg; struct crypto_user_alg *p = nlmsg_data(nlh); + int err; if (!netlink_capable(skb, CAP_NET_ADMIN)) return -EPERM; @@ -310,13 +321,19 @@ static int crypto_del_alg(struct sk_buff *skb, struct nlmsghdr *nlh, * if we try to unregister. Unregistering such an algorithm without * removing the module is not possible, so we restrict to crypto * instances that are build from templates. */ + err = -EINVAL; if (!(alg->cra_flags & CRYPTO_ALG_INSTANCE)) - return -EINVAL; + goto drop_alg; - if (atomic_read(&alg->cra_refcnt) != 1) - return -EBUSY; + err = -EBUSY; + if (atomic_read(&alg->cra_refcnt) > 2) + goto drop_alg; - return crypto_unregister_instance((struct crypto_instance *)alg); + err = crypto_unregister_instance((struct crypto_instance *)alg); + +drop_alg: + crypto_mod_put(alg); + return err; } static struct crypto_alg *crypto_user_skcipher_alg(const char *name, u32 type, @@ -395,8 +412,10 @@ static int crypto_add_alg(struct sk_buff *skb, struct nlmsghdr *nlh, return -EINVAL; alg = crypto_alg_match(p, exact); - if (alg) + if (alg) { + crypto_mod_put(alg); return -EEXIST; + } if (strlen(p->cru_driver_name)) name = p->cru_driver_name; -- cgit v1.2.3-59-g8ed1b