3.16.79-rc1 review patch. If anyone has any objections, please let me know.
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From: Herbert Xu herbert@gondor.apana.org.au
commit 016baaa1183bb0c5fb2a7de42413bba8a51c1bc8 upstream.
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 herbert@gondor.apana.org.au [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- crypto/crypto_user.c | 39 +++++++++++++++++++++++++++++---------- 1 file changed, 29 insertions(+), 10 deletions(-)
--- a/crypto/crypto_user.c +++ b/crypto/crypto_user.c @@ -65,10 +65,14 @@ static struct crypto_alg *crypto_alg_mat 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); @@ -211,9 +215,10 @@ static int crypto_report(struct sk_buff 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; @@ -221,6 +226,10 @@ static int crypto_report(struct sk_buff info.nlmsg_flags = 0;
err = crypto_report_alg(alg, &info); + +drop_alg: + crypto_mod_put(alg); + if (err) return err;
@@ -293,6 +302,7 @@ static int crypto_update_alg(struct sk_b
up_write(&crypto_alg_sem);
+ crypto_mod_put(alg); crypto_remove_final(&list);
return 0; @@ -303,6 +313,7 @@ static int crypto_del_alg(struct sk_buff { struct crypto_alg *alg; struct crypto_user_alg *p = nlmsg_data(nlh); + int err;
if (!netlink_capable(skb, CAP_NET_ADMIN)) return -EPERM; @@ -319,13 +330,19 @@ static int crypto_del_alg(struct sk_buff * 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(alg); + err = crypto_unregister_instance(alg); + +drop_alg: + crypto_mod_put(alg); + return err; }
static struct crypto_alg *crypto_user_skcipher_alg(const char *name, u32 type, @@ -404,8 +421,10 @@ static int crypto_add_alg(struct sk_buff 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;