[ 025/143] crypto: api - Fix race condition in larval lookup

[Willy Tarreau]

2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------

From: Nikola Pajkovsky <npajkovs@xxxxxxxxxx>

https://bugzilla.redhat.com/1016108

64z is missing rhel6 commit 3af031a395c0 ("[crypto] algboss: Hold ref
count on larval") which is causing cosmetic fuzz, because crypto_alg_get
was move from crypto/api.c to crypto/internal.h.

From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>

[ upstream commit 77dbd7a95e4a4f15264c333a9e9ab97ee27dc2aa ]

crypto_larval_lookup should only return a larval if it created one.
Any larval created by another entity must be processed through
crypto_larval_wait before being returned.

Otherwise this will lead to a larval being killed twice, which
will most likely lead to a crash.

Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Kees Cook <keescook@xxxxxxxxxxxx>
Tested-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Nikola Pajkovsky <npajkovs@xxxxxxxxxx>
Signed-off-by: Willy Tarreau <w@xxxxxx>
---
 crypto/api.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/crypto/api.c b/crypto/api.c
index 798526d..f4be65f 100644
--- a/crypto/api.c
+++ b/crypto/api.c
@@ -40,6 +40,8 @@ static inline struct crypto_alg *crypto_alg_get(struct crypto_alg *alg)
 	return alg;
 }
 
+static struct crypto_alg *crypto_larval_wait(struct crypto_alg *alg);
+
 struct crypto_alg *crypto_mod_get(struct crypto_alg *alg)
 {
 	return try_module_get(alg->cra_module) ? crypto_alg_get(alg) : NULL;
@@ -150,8 +152,11 @@ static struct crypto_alg *crypto_larval_add(const char *name, u32 type,
 	}
 	up_write(&crypto_alg_sem);
 
-	if (alg != &larval->alg)
+	if (alg != &larval->alg) {
 		kfree(larval);
+		if (crypto_is_larval(alg))
+			alg = crypto_larval_wait(alg);
+	}
 
 	return alg;
 }
-- 
1.7.12.2.21.g234cd45.dirty



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