In preparation to enabling -Wvla, remove VLAs and replace them
with dynamic memory allocation instead.

The use of stack Variable Length Arrays needs to be avoided, as they
can be a vector for stack exhaustion, which can be both a runtime bug
or a security flaw. Also, in general, as code evolves it is easy to
lose track of how big a VLA can get. Thus, we can end up having runtime
failures that are hard to debug.

Also, fixed as part of the directive to remove all VLAs from
the kernel: https://lkml.org/lkml/2018/3/7/621

Signed-off-by: Gustavo A. R. Silva <gust...@embeddedor.com>
---
 net/mac80211/aes_cmac.c | 36 ++++++++++++++++++++++++------------
 1 file changed, 24 insertions(+), 12 deletions(-)

diff --git a/net/mac80211/aes_cmac.c b/net/mac80211/aes_cmac.c
index 2fb6558..c9444bf 100644
--- a/net/mac80211/aes_cmac.c
+++ b/net/mac80211/aes_cmac.c
@@ -27,30 +27,42 @@ static const u8 zero[CMAC_TLEN_256];
 void ieee80211_aes_cmac(struct crypto_shash *tfm, const u8 *aad,
                        const u8 *data, size_t data_len, u8 *mic)
 {
-       SHASH_DESC_ON_STACK(desc, tfm);
+       struct shash_desc *shash;
        u8 out[AES_BLOCK_SIZE];
 
-       desc->tfm = tfm;
+       shash = kmalloc(sizeof(*shash) + crypto_shash_descsize(tfm),
+                       GFP_KERNEL);
+       if (!shash)
+               return;
 
-       crypto_shash_init(desc);
-       crypto_shash_update(desc, aad, AAD_LEN);
-       crypto_shash_update(desc, data, data_len - CMAC_TLEN);
-       crypto_shash_finup(desc, zero, CMAC_TLEN, out);
+       shash->tfm = tfm;
+
+       crypto_shash_init(shash);
+       crypto_shash_update(shash, aad, AAD_LEN);
+       crypto_shash_update(shash, data, data_len - CMAC_TLEN);
+       crypto_shash_finup(shash, zero, CMAC_TLEN, out);
 
        memcpy(mic, out, CMAC_TLEN);
+       kfree(shash);
 }
 
 void ieee80211_aes_cmac_256(struct crypto_shash *tfm, const u8 *aad,
                            const u8 *data, size_t data_len, u8 *mic)
 {
-       SHASH_DESC_ON_STACK(desc, tfm);
+       struct shash_desc *shash;
+
+       shash = kmalloc(sizeof(*shash) + crypto_shash_descsize(tfm),
+                       GFP_KERNEL);
+       if (!shash)
+               return;
 
-       desc->tfm = tfm;
+       shash->tfm = tfm;
 
-       crypto_shash_init(desc);
-       crypto_shash_update(desc, aad, AAD_LEN);
-       crypto_shash_update(desc, data, data_len - CMAC_TLEN_256);
-       crypto_shash_finup(desc, zero, CMAC_TLEN_256, mic);
+       crypto_shash_init(shash);
+       crypto_shash_update(shash, aad, AAD_LEN);
+       crypto_shash_update(shash, data, data_len - CMAC_TLEN_256);
+       crypto_shash_finup(shash, zero, CMAC_TLEN_256, mic);
+       kfree(shash);
 }
 
 struct crypto_shash *ieee80211_aes_cmac_key_setup(const u8 key[],
-- 
2.7.4

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