crypto: s390 - fix des and des3_ede ctr concurrency issue

commit ee97dc7db4cbda33e4241c2d85b42d1835bc8a35 upstream.

In s390 des and 3des ctr mode there is one preallocated page
used to speed up the en/decryption. This page is not protected
against concurrent usage and thus there is a potential of data
corruption with multiple threads.

The fix introduces locking/unlocking the ctr page and a slower
fallback solution at concurrency situations.

Signed-off-by: Harald Freudenberger <freude@linux.vnet.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/arch/s390/crypto/des_s390.c b/arch/s390/crypto/des_s390.c
index 5fe77d5..991fb7d 100644 (file)
--- a/arch/s390/crypto/des_s390.c
+++ b/arch/s390/crypto/des_s390.c
@@ -25,6 +25,7 @@
 #define DES3_KEY_SIZE  (3 * DES_KEY_SIZE)
 
 static u8 *ctrblk;
+static DEFINE_SPINLOCK(ctrblk_lock);
 
 struct s390_des_ctx {
        u8 iv[DES_BLOCK_SIZE];
@@ -376,54 +377,80 @@ static struct crypto_alg cbc_des3_alg = {
        }
 };
 
+static unsigned int __ctrblk_init(u8 *ctrptr, unsigned int nbytes)
+{
+       unsigned int i, n;
+
+       /* align to block size, max. PAGE_SIZE */
+       n = (nbytes > PAGE_SIZE) ? PAGE_SIZE : nbytes & ~(DES_BLOCK_SIZE - 1);
+       for (i = DES_BLOCK_SIZE; i < n; i += DES_BLOCK_SIZE) {
+               memcpy(ctrptr + i, ctrptr + i - DES_BLOCK_SIZE, DES_BLOCK_SIZE);
+               crypto_inc(ctrptr + i, DES_BLOCK_SIZE);
+       }
+       return n;
+}
+
 static int ctr_desall_crypt(struct blkcipher_desc *desc, long func,
-                           struct s390_des_ctx *ctx, struct blkcipher_walk *walk)
+                           struct s390_des_ctx *ctx,
+                           struct blkcipher_walk *walk)
 {
        int ret = blkcipher_walk_virt_block(desc, walk, DES_BLOCK_SIZE);
-       unsigned int i, n, nbytes;
-       u8 buf[DES_BLOCK_SIZE];
-       u8 *out, *in;
+       unsigned int n, nbytes;
+       u8 buf[DES_BLOCK_SIZE], ctrbuf[DES_BLOCK_SIZE];
+       u8 *out, *in, *ctrptr = ctrbuf;
+
+       if (!walk->nbytes)
+               return ret;
 
-       memcpy(ctrblk, walk->iv, DES_BLOCK_SIZE);
+       if (spin_trylock(&ctrblk_lock))
+               ctrptr = ctrblk;
+
+       memcpy(ctrptr, walk->iv, DES_BLOCK_SIZE);
        while ((nbytes = walk->nbytes) >= DES_BLOCK_SIZE) {
                out = walk->dst.virt.addr;
                in = walk->src.virt.addr;
                while (nbytes >= DES_BLOCK_SIZE) {
-                       /* align to block size, max. PAGE_SIZE */
-                       n = (nbytes > PAGE_SIZE) ? PAGE_SIZE :
-                               nbytes & ~(DES_BLOCK_SIZE - 1);
-                       for (i = DES_BLOCK_SIZE; i < n; i += DES_BLOCK_SIZE) {
-                               memcpy(ctrblk + i, ctrblk + i - DES_BLOCK_SIZE,
-                                      DES_BLOCK_SIZE);
-                               crypto_inc(ctrblk + i, DES_BLOCK_SIZE);
-                       }
-                       ret = crypt_s390_kmctr(func, ctx->key, out, in, n, ctrblk);
-                       if (ret < 0 || ret != n)
+                       if (ctrptr == ctrblk)
+                               n = __ctrblk_init(ctrptr, nbytes);
+                       else
+                               n = DES_BLOCK_SIZE;
+                       ret = crypt_s390_kmctr(func, ctx->key, out, in,
+                                              n, ctrptr);
+                       if (ret < 0 || ret != n) {
+                               if (ctrptr == ctrblk)
+                                       spin_unlock(&ctrblk_lock);
                                return -EIO;
+                       }
                        if (n > DES_BLOCK_SIZE)
-                               memcpy(ctrblk, ctrblk + n - DES_BLOCK_SIZE,
+                               memcpy(ctrptr, ctrptr + n - DES_BLOCK_SIZE,
                                       DES_BLOCK_SIZE);
-                       crypto_inc(ctrblk, DES_BLOCK_SIZE);
+                       crypto_inc(ctrptr, DES_BLOCK_SIZE);
                        out += n;
                        in += n;
                        nbytes -= n;
                }
                ret = blkcipher_walk_done(desc, walk, nbytes);
        }
-
+       if (ctrptr == ctrblk) {
+               if (nbytes)
+                       memcpy(ctrbuf, ctrptr, DES_BLOCK_SIZE);
+               else
+                       memcpy(walk->iv, ctrptr, DES_BLOCK_SIZE);
+               spin_unlock(&ctrblk_lock);
+       }
        /* final block may be < DES_BLOCK_SIZE, copy only nbytes */
        if (nbytes) {
                out = walk->dst.virt.addr;
                in = walk->src.virt.addr;
                ret = crypt_s390_kmctr(func, ctx->key, buf, in,
-                                      DES_BLOCK_SIZE, ctrblk);
+                                      DES_BLOCK_SIZE, ctrbuf);
                if (ret < 0 || ret != DES_BLOCK_SIZE)
                        return -EIO;
                memcpy(out, buf, nbytes);
-               crypto_inc(ctrblk, DES_BLOCK_SIZE);
+               crypto_inc(ctrbuf, DES_BLOCK_SIZE);
                ret = blkcipher_walk_done(desc, walk, 0);
+               memcpy(walk->iv, ctrbuf, DES_BLOCK_SIZE);
        }
-       memcpy(walk->iv, ctrblk, DES_BLOCK_SIZE);
        return ret;
 }