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authorHerbert Xu <herbert@gondor.apana.org.au>2020-06-08 16:48:43 +1000
committerHerbert Xu <herbert@gondor.apana.org.au>2020-06-18 17:09:54 +1000
commit34c86f4c4a7be3b3e35aa48bd18299d4c756064d (patch)
treef228827d837f16799bbab27d118d1f1fd373c799 /crypto/algif_hash.c
parent819966c06b759022e9932f328284314d9272b9f3 (diff)
downloadlwn-34c86f4c4a7be3b3e35aa48bd18299d4c756064d.tar.gz
lwn-34c86f4c4a7be3b3e35aa48bd18299d4c756064d.zip
crypto: af_alg - fix use-after-free in af_alg_accept() due to bh_lock_sock()
The locking in af_alg_release_parent is broken as the BH socket lock can only be taken if there is a code-path to handle the case where the lock is owned by process-context. Instead of adding such handling, we can fix this by changing the ref counts to atomic_t. This patch also modifies the main refcnt to include both normal and nokey sockets. This way we don't have to fudge the nokey ref count when a socket changes from nokey to normal. Credits go to Mauricio Faria de Oliveira who diagnosed this bug and sent a patch for it: https://lore.kernel.org/linux-crypto/20200605161657.535043-1-mfo@canonical.com/ Reported-by: Brian Moyles <bmoyles@netflix.com> Reported-by: Mauricio Faria de Oliveira <mfo@canonical.com> Fixes: 37f96694cf73 ("crypto: af_alg - Use bh_lock_sock in...") Cc: <stable@vger.kernel.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'crypto/algif_hash.c')
-rw-r--r--crypto/algif_hash.c9
1 files changed, 3 insertions, 6 deletions
diff --git a/crypto/algif_hash.c b/crypto/algif_hash.c
index da1ffa4f7f8d..e71727c25a7d 100644
--- a/crypto/algif_hash.c
+++ b/crypto/algif_hash.c
@@ -301,7 +301,7 @@ static int hash_check_key(struct socket *sock)
struct alg_sock *ask = alg_sk(sk);
lock_sock(sk);
- if (ask->refcnt)
+ if (!atomic_read(&ask->nokey_refcnt))
goto unlock_child;
psk = ask->parent;
@@ -313,11 +313,8 @@ static int hash_check_key(struct socket *sock)
if (crypto_ahash_get_flags(tfm) & CRYPTO_TFM_NEED_KEY)
goto unlock;
- if (!pask->refcnt++)
- sock_hold(psk);
-
- ask->refcnt = 1;
- sock_put(psk);
+ atomic_dec(&pask->nokey_refcnt);
+ atomic_set(&ask->nokey_refcnt, 0);
err = 0;