Re: [PATCH] sunrpc: don't pass on-stack memory to sg_set_buf

[Fields Bruce James <bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org>]

On Tue, Oct 25, 2016 at 09:47:16PM +0000, Trond Myklebust wrote:
> 
> > On Oct 25, 2016, at 15:59, Fields Bruce James <bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org> wrote:
> > 
> > On Tue, Oct 25, 2016 at 07:34:43PM +0000, Trond Myklebust wrote:
> >> NACK…  I agree that there may already be borkage in RPCSEC_GSS-land, but that’s not a reason to be adding to the pile of things that need to be fixed… The allocations that lie in the RPC client’s encode/decode path do need to be GFP_NOFS….
> > 
> > OK.  Any disadvantage to keeping this patch with just GFP_NOFS
> > allocations everywhere that might be in the write path?
> 
> It’s what we have to do everywhere else in the RPC client, so I can’t see why it should be a problem.

OK, the below is what I intend to merge if nobody spots another problem.

--b.

commit 2876a34466ce
Author: J. Bruce Fields <bfields-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Date:   Tue Oct 18 16:30:09 2016 -0400

    sunrpc: don't pass on-stack memory to sg_set_buf
    
    As of ac4e97abce9b "scatterlist: sg_set_buf() argument must be in linear
    mapping", sg_set_buf hits a BUG when make_checksum_v2->xdr_process_buf,
    among other callers, passes it memory on the stack.
    
    We only need a scatterlist to pass this to the crypto code, and it seems
    like overkill to require kmalloc'd memory just to encrypt a few bytes,
    but for now this seems the best fix.
    
    Many of these callers are in the NFS write paths, so we allocate with
    GFP_NOFS.  It might be possible to do without allocations here entirely,
    but that would probably be a bigger project.
    
    Cc: Rusty Russell <rusty-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
    Signed-off-by: J. Bruce Fields <bfields-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
index d8bd97a5a7c9..3dfd769dc5b5 100644
--- a/net/sunrpc/auth_gss/auth_gss.c
+++ b/net/sunrpc/auth_gss/auth_gss.c
@@ -1616,7 +1616,7 @@ gss_validate(struct rpc_task *task, __be32 *p)
 {
 	struct rpc_cred *cred = task->tk_rqstp->rq_cred;
 	struct gss_cl_ctx *ctx = gss_cred_get_ctx(cred);
-	__be32		seq;
+	__be32		*seq = NULL;
 	struct kvec	iov;
 	struct xdr_buf	verf_buf;
 	struct xdr_netobj mic;
@@ -1631,9 +1631,12 @@ gss_validate(struct rpc_task *task, __be32 *p)
 		goto out_bad;
 	if (flav != RPC_AUTH_GSS)
 		goto out_bad;
-	seq = htonl(task->tk_rqstp->rq_seqno);
-	iov.iov_base = &seq;
-	iov.iov_len = sizeof(seq);
+	seq = kmalloc(4, GFP_NOFS);
+	if (!seq)
+		goto out_bad;
+	*seq = htonl(task->tk_rqstp->rq_seqno);
+	iov.iov_base = seq;
+	iov.iov_len = 4;
 	xdr_buf_from_iov(&iov, &verf_buf);
 	mic.data = (u8 *)p;
 	mic.len = len;
@@ -1653,11 +1656,13 @@ gss_validate(struct rpc_task *task, __be32 *p)
 	gss_put_ctx(ctx);
 	dprintk("RPC: %5u %s: gss_verify_mic succeeded.\n",
 			task->tk_pid, __func__);
+	kfree(seq);
 	return p + XDR_QUADLEN(len);
 out_bad:
 	gss_put_ctx(ctx);
 	dprintk("RPC: %5u %s failed ret %ld.\n", task->tk_pid, __func__,
 		PTR_ERR(ret));
+	kfree(seq);
 	return ret;
 }
 
diff --git a/net/sunrpc/auth_gss/gss_krb5_crypto.c b/net/sunrpc/auth_gss/gss_krb5_crypto.c
index 244245bcbbd2..90115ceefd49 100644
--- a/net/sunrpc/auth_gss/gss_krb5_crypto.c
+++ b/net/sunrpc/auth_gss/gss_krb5_crypto.c
@@ -166,8 +166,8 @@ make_checksum_hmac_md5(struct krb5_ctx *kctx, char *header, int hdrlen,
 		       unsigned int usage, struct xdr_netobj *cksumout)
 {
 	struct scatterlist              sg[1];
-	int err;
-	u8 checksumdata[GSS_KRB5_MAX_CKSUM_LEN];
+	int err = -1;
+	u8 *checksumdata;
 	u8 rc4salt[4];
 	struct crypto_ahash *md5;
 	struct crypto_ahash *hmac_md5;
@@ -187,23 +187,22 @@ make_checksum_hmac_md5(struct krb5_ctx *kctx, char *header, int hdrlen,
 		return GSS_S_FAILURE;
 	}
 
+	checksumdata = kmalloc(GSS_KRB5_MAX_CKSUM_LEN, GFP_NOFS);
+	if (!checksumdata)
+		return GSS_S_FAILURE;
+
 	md5 = crypto_alloc_ahash("md5", 0, CRYPTO_ALG_ASYNC);
 	if (IS_ERR(md5))
-		return GSS_S_FAILURE;
+		goto out_free_cksum;
 
 	hmac_md5 = crypto_alloc_ahash(kctx->gk5e->cksum_name, 0,
 				      CRYPTO_ALG_ASYNC);
-	if (IS_ERR(hmac_md5)) {
-		crypto_free_ahash(md5);
-		return GSS_S_FAILURE;
-	}
+	if (IS_ERR(hmac_md5))
+		goto out_free_md5;
 
 	req = ahash_request_alloc(md5, GFP_KERNEL);
-	if (!req) {
-		crypto_free_ahash(hmac_md5);
-		crypto_free_ahash(md5);
-		return GSS_S_FAILURE;
-	}
+	if (!req)
+		goto out_free_hmac_md5;
 
 	ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL, NULL);
 
@@ -232,11 +231,8 @@ make_checksum_hmac_md5(struct krb5_ctx *kctx, char *header, int hdrlen,
 
 	ahash_request_free(req);
 	req = ahash_request_alloc(hmac_md5, GFP_KERNEL);
-	if (!req) {
-		crypto_free_ahash(hmac_md5);
-		crypto_free_ahash(md5);
-		return GSS_S_FAILURE;
-	}
+	if (!req)
+		goto out_free_hmac_md5;
 
 	ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL, NULL);
 
@@ -258,8 +254,12 @@ make_checksum_hmac_md5(struct krb5_ctx *kctx, char *header, int hdrlen,
 	cksumout->len = kctx->gk5e->cksumlength;
 out:
 	ahash_request_free(req);
-	crypto_free_ahash(md5);
+out_free_hmac_md5:
 	crypto_free_ahash(hmac_md5);
+out_free_md5:
+	crypto_free_ahash(md5);
+out_free_cksum:
+	kfree(checksumdata);
 	return err ? GSS_S_FAILURE : 0;
 }
 
@@ -276,8 +276,8 @@ make_checksum(struct krb5_ctx *kctx, char *header, int hdrlen,
 	struct crypto_ahash *tfm;
 	struct ahash_request *req;
 	struct scatterlist              sg[1];
-	int err;
-	u8 checksumdata[GSS_KRB5_MAX_CKSUM_LEN];
+	int err = -1;
+	u8 *checksumdata;
 	unsigned int checksumlen;
 
 	if (kctx->gk5e->ctype == CKSUMTYPE_HMAC_MD5_ARCFOUR)
@@ -291,15 +291,17 @@ make_checksum(struct krb5_ctx *kctx, char *header, int hdrlen,
 		return GSS_S_FAILURE;
 	}
 
+	checksumdata = kmalloc(GSS_KRB5_MAX_CKSUM_LEN, GFP_NOFS);
+	if (checksumdata == NULL)
+		return GSS_S_FAILURE;
+
 	tfm = crypto_alloc_ahash(kctx->gk5e->cksum_name, 0, CRYPTO_ALG_ASYNC);
 	if (IS_ERR(tfm))
-		return GSS_S_FAILURE;
+		goto out_free_cksum;
 
 	req = ahash_request_alloc(tfm, GFP_KERNEL);
-	if (!req) {
-		crypto_free_ahash(tfm);
-		return GSS_S_FAILURE;
-	}
+	if (!req)
+		goto out_free_ahash;
 
 	ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL, NULL);
 
@@ -349,7 +351,10 @@ make_checksum(struct krb5_ctx *kctx, char *header, int hdrlen,
 	cksumout->len = kctx->gk5e->cksumlength;
 out:
 	ahash_request_free(req);
+out_free_ahash:
 	crypto_free_ahash(tfm);
+out_free_cksum:
+	kfree(checksumdata);
 	return err ? GSS_S_FAILURE : 0;
 }
 
@@ -368,8 +373,8 @@ make_checksum_v2(struct krb5_ctx *kctx, char *header, int hdrlen,
 	struct crypto_ahash *tfm;
 	struct ahash_request *req;
 	struct scatterlist sg[1];
-	int err;
-	u8 checksumdata[GSS_KRB5_MAX_CKSUM_LEN];
+	int err = -1;
+	u8 *checksumdata;
 	unsigned int checksumlen;
 
 	if (kctx->gk5e->keyed_cksum == 0) {
@@ -383,16 +388,18 @@ make_checksum_v2(struct krb5_ctx *kctx, char *header, int hdrlen,
 		return GSS_S_FAILURE;
 	}
 
+	checksumdata = kmalloc(GSS_KRB5_MAX_CKSUM_LEN, GFP_NOFS);
+	if (!checksumdata)
+		return GSS_S_FAILURE;
+
 	tfm = crypto_alloc_ahash(kctx->gk5e->cksum_name, 0, CRYPTO_ALG_ASYNC);
 	if (IS_ERR(tfm))
-		return GSS_S_FAILURE;
+		goto out_free_cksum;
 	checksumlen = crypto_ahash_digestsize(tfm);
 
 	req = ahash_request_alloc(tfm, GFP_KERNEL);
-	if (!req) {
-		crypto_free_ahash(tfm);
-		return GSS_S_FAILURE;
-	}
+	if (!req)
+		goto out_free_ahash;
 
 	ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL, NULL);
 
@@ -433,7 +440,10 @@ make_checksum_v2(struct krb5_ctx *kctx, char *header, int hdrlen,
 	}
 out:
 	ahash_request_free(req);
+out_free_ahash:
 	crypto_free_ahash(tfm);
+out_free_cksum:
+	kfree(checksumdata);
 	return err ? GSS_S_FAILURE : 0;
 }
 
@@ -666,14 +676,17 @@ gss_krb5_cts_crypt(struct crypto_skcipher *cipher, struct xdr_buf *buf,
 	u32 ret;
 	struct scatterlist sg[1];
 	SKCIPHER_REQUEST_ON_STACK(req, cipher);
-	u8 data[GSS_KRB5_MAX_BLOCKSIZE * 2];
+	u8 *data;
 	struct page **save_pages;
 	u32 len = buf->len - offset;
 
-	if (len > ARRAY_SIZE(data)) {
+	if (len > GSS_KRB5_MAX_BLOCKSIZE * 2) {
 		WARN_ON(0);
 		return -ENOMEM;
 	}
+	data = kmalloc(GSS_KRB5_MAX_BLOCKSIZE * 2, GFP_NOFS);
+	if (!data)
+		return -ENOMEM;
 
 	/*
 	 * For encryption, we want to read from the cleartext
@@ -708,6 +721,7 @@ gss_krb5_cts_crypt(struct crypto_skcipher *cipher, struct xdr_buf *buf,
 	ret = write_bytes_to_xdr_buf(buf, offset, data, len);
 
 out:
+	kfree(data);
 	return ret;
 }
 
diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
index d67f7e1bc82d..45662d7f0943 100644
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -718,30 +718,37 @@ gss_write_null_verf(struct svc_rqst *rqstp)
 static int
 gss_write_verf(struct svc_rqst *rqstp, struct gss_ctx *ctx_id, u32 seq)
 {
-	__be32			xdr_seq;
+	__be32			*xdr_seq;
 	u32			maj_stat;
 	struct xdr_buf		verf_data;
 	struct xdr_netobj	mic;
 	__be32			*p;
 	struct kvec		iov;
+	int err = -1;
 
 	svc_putnl(rqstp->rq_res.head, RPC_AUTH_GSS);
-	xdr_seq = htonl(seq);
+	xdr_seq = kmalloc(4, GFP_KERNEL);
+	if (!xdr_seq)
+		return -1;
+	*xdr_seq = htonl(seq);
 
-	iov.iov_base = &xdr_seq;
-	iov.iov_len = sizeof(xdr_seq);
+	iov.iov_base = xdr_seq;
+	iov.iov_len = 4;
 	xdr_buf_from_iov(&iov, &verf_data);
 	p = rqstp->rq_res.head->iov_base + rqstp->rq_res.head->iov_len;
 	mic.data = (u8 *)(p + 1);
 	maj_stat = gss_get_mic(ctx_id, &verf_data, &mic);
 	if (maj_stat != GSS_S_COMPLETE)
-		return -1;
+		goto out;
 	*p++ = htonl(mic.len);
 	memset((u8 *)p + mic.len, 0, round_up_to_quad(mic.len) - mic.len);
 	p += XDR_QUADLEN(mic.len);
 	if (!xdr_ressize_check(rqstp, p))
-		return -1;
-	return 0;
+		goto out;
+	err = 0;
+out:
+	kfree(xdr_seq);
+	return err;
 }
 
 struct gss_domain {
--
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