We avoid 2 VLAs[1] by always allocating MAX_BLOCKSIZE + MAX_ALIGNMASK bytes. We also check the selected cipher at instance creation time, if it doesn't comply with these limits, the creation will fail.
[1] http://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qpxydaacu1rq...@mail.gmail.com Signed-off-by: Salvatore Mesoraca <s.mesorac...@gmail.com> --- crypto/ctr.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/crypto/ctr.c b/crypto/ctr.c index 854d924..ce62552 100644 --- a/crypto/ctr.c +++ b/crypto/ctr.c @@ -20,6 +20,7 @@ #include <linux/random.h> #include <linux/scatterlist.h> #include <linux/slab.h> +#include "internal.h" struct crypto_ctr_ctx { struct crypto_cipher *child; @@ -58,7 +59,7 @@ static void crypto_ctr_crypt_final(struct blkcipher_walk *walk, unsigned int bsize = crypto_cipher_blocksize(tfm); unsigned long alignmask = crypto_cipher_alignmask(tfm); u8 *ctrblk = walk->iv; - u8 tmp[bsize + alignmask]; + u8 tmp[MAX_BLOCKSIZE + MAX_ALIGNMASK]; u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1); u8 *src = walk->src.virt.addr; u8 *dst = walk->dst.virt.addr; @@ -106,7 +107,7 @@ static int crypto_ctr_crypt_inplace(struct blkcipher_walk *walk, unsigned int nbytes = walk->nbytes; u8 *ctrblk = walk->iv; u8 *src = walk->src.virt.addr; - u8 tmp[bsize + alignmask]; + u8 tmp[MAX_BLOCKSIZE + MAX_ALIGNMASK]; u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1); do { @@ -206,6 +207,14 @@ static struct crypto_instance *crypto_ctr_alloc(struct rtattr **tb) if (alg->cra_blocksize < 4) goto out_put_alg; + /* Block size must be <= MAX_BLOCKSIZE. */ + if (alg->cra_blocksize > MAX_BLOCKSIZE) + goto out_put_alg; + + /* Alignmask must be <= MAX_ALIGNMASK. */ + if (alg->cra_alignmask > MAX_ALIGNMASK) + goto out_put_alg; + /* If this is false we'd fail the alignment of crypto_inc. */ if (alg->cra_blocksize % 4) goto out_put_alg; -- 1.9.1
