From 625146d9fbb74651e6158af7db0e76b899c39c9e Mon Sep 17 00:00:00 2001 From: Matt Caswell Date: Thu, 12 Nov 2015 10:52:30 +0000 Subject: [PATCH] Fix async deadlock problem The rand code can aquire locks and then attempt crypto operations. This can end up in a deadlock if we are using an async engine, because control returns back to the user code whilst still holding the lock. We need to force synchronous operation for these sections of code. Reviewed-by: Rich Salz --- crypto/rand/md_rand.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/crypto/rand/md_rand.c b/crypto/rand/md_rand.c index 0eaaf62863..698a63892e 100644 --- a/crypto/rand/md_rand.c +++ b/crypto/rand/md_rand.c @@ -130,6 +130,7 @@ #include #include +#include #include "rand_lcl.h" #include @@ -432,6 +433,11 @@ static int rand_bytes(unsigned char *buf, int num, int pseudo) */ CRYPTO_w_lock(CRYPTO_LOCK_RAND); + /* + * We could end up in an async engine while holding this lock so ensure + * we don't pause and cause a deadlock + */ + ASYNC_block_pause(); /* prevent rand_bytes() from trying to obtain the lock again */ CRYPTO_w_lock(CRYPTO_LOCK_RAND2); @@ -510,6 +516,7 @@ static int rand_bytes(unsigned char *buf, int num, int pseudo) /* before unlocking, we must clear 'crypto_lock_rand' */ crypto_lock_rand = 0; + ASYNC_unblock_pause(); CRYPTO_w_unlock(CRYPTO_LOCK_RAND); while (num > 0) { @@ -576,10 +583,15 @@ static int rand_bytes(unsigned char *buf, int num, int pseudo) || !MD_Update(&m, local_md, MD_DIGEST_LENGTH)) goto err; CRYPTO_w_lock(CRYPTO_LOCK_RAND); + /* + * Prevent deadlocks if we end up in an async engine + */ + ASYNC_block_pause(); if (!MD_Update(&m, md, MD_DIGEST_LENGTH) || !MD_Final(&m, md)) { CRYPTO_w_unlock(CRYPTO_LOCK_RAND); goto err; } + ASYNC_unblock_pause(); CRYPTO_w_unlock(CRYPTO_LOCK_RAND); EVP_MD_CTX_cleanup(&m); @@ -635,6 +647,10 @@ static int rand_status(void) if (!do_not_lock) { CRYPTO_w_lock(CRYPTO_LOCK_RAND); + /* + * Prevent deadlocks in case we end up in an async engine + */ + ASYNC_block_pause(); /* * prevent rand_bytes() from trying to obtain the lock again @@ -656,6 +672,7 @@ static int rand_status(void) /* before unlocking, we must clear 'crypto_lock_rand' */ crypto_lock_rand = 0; + ASYNC_unblock_pause(); CRYPTO_w_unlock(CRYPTO_LOCK_RAND); } -- 2.25.1