[PATCH 4.14] sunrpc: fix 4 more call sites that were using stack memory with a scatterlist

[Scott Mayhew <smayhew@xxxxxxxxxx>]

(cherry picked from commit e7afe6c1d486b516ed586dcc10b3e7e3e85a9c2b)

While trying to reproduce a reported kernel panic on arm64, I discovered
that AUTH_GSS basically doesn't work at all with older enctypes on arm64
systems with CONFIG_VMAP_STACK enabled.  It turns out there still a few
places using stack memory with scatterlists, causing krb5_encrypt() and
krb5_decrypt() to produce incorrect results (or a BUG if CONFIG_DEBUG_SG
is enabled).

Tested with cthon on v4.0/v4.1/v4.2 with krb5/krb5i/krb5p using
des3-cbc-sha1 and arcfour-hmac-md5.

Signed-off-by: Scott Mayhew <smayhew@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>

Conflicts:
	net/sunrpc/auth_gss/gss_krb5_seqnum.c
---
 net/sunrpc/auth_gss/gss_krb5_seqnum.c | 49 +++++++++++++++++++++++++++--------
 1 file changed, 38 insertions(+), 11 deletions(-)

diff --git a/net/sunrpc/auth_gss/gss_krb5_seqnum.c b/net/sunrpc/auth_gss/gss_krb5_seqnum.c
index c8b9082..2d2ed67 100644
--- a/net/sunrpc/auth_gss/gss_krb5_seqnum.c
+++ b/net/sunrpc/auth_gss/gss_krb5_seqnum.c
@@ -44,7 +44,7 @@
 		      unsigned char *cksum, unsigned char *buf)
 {
 	struct crypto_skcipher *cipher;
-	unsigned char plain[8];
+	unsigned char *plain;
 	s32 code;
 
 	dprintk("RPC:       %s:\n", __func__);
@@ -53,6 +53,10 @@
 	if (IS_ERR(cipher))
 		return PTR_ERR(cipher);
 
+	plain = kmalloc(8, GFP_NOFS);
+	if (!plain)
+		return -ENOMEM;
+
 	plain[0] = (unsigned char) ((seqnum >> 24) & 0xff);
 	plain[1] = (unsigned char) ((seqnum >> 16) & 0xff);
 	plain[2] = (unsigned char) ((seqnum >> 8) & 0xff);
@@ -69,6 +73,7 @@
 	code = krb5_encrypt(cipher, cksum, plain, buf, 8);
 out:
 	crypto_free_skcipher(cipher);
+	kfree(plain);
 	return code;
 }
 s32
@@ -78,12 +83,17 @@
 		u32 seqnum,
 		unsigned char *cksum, unsigned char *buf)
 {
-	unsigned char plain[8];
+	unsigned char *plain;
+	s32 code;
 
 	if (kctx->enctype == ENCTYPE_ARCFOUR_HMAC)
 		return krb5_make_rc4_seq_num(kctx, direction, seqnum,
 					     cksum, buf);
 
+	plain = kmalloc(8, GFP_NOFS);
+	if (!plain)
+		return -ENOMEM;
+
 	plain[0] = (unsigned char) (seqnum & 0xff);
 	plain[1] = (unsigned char) ((seqnum >> 8) & 0xff);
 	plain[2] = (unsigned char) ((seqnum >> 16) & 0xff);
@@ -94,7 +104,9 @@
 	plain[6] = direction;
 	plain[7] = direction;
 
-	return krb5_encrypt(key, cksum, plain, buf, 8);
+	code = krb5_encrypt(key, cksum, plain, buf, 8);
+	kfree(plain);
+	return code;
 }
 
 static s32
@@ -102,7 +114,7 @@
 		     unsigned char *buf, int *direction, s32 *seqnum)
 {
 	struct crypto_skcipher *cipher;
-	unsigned char plain[8];
+	unsigned char *plain;
 	s32 code;
 
 	dprintk("RPC:       %s:\n", __func__);
@@ -115,20 +127,28 @@
 	if (code)
 		goto out;
 
+	plain = kmalloc(8, GFP_NOFS);
+	if (!plain) {
+		code = -ENOMEM;
+		goto out;
+	}
+
 	code = krb5_decrypt(cipher, cksum, buf, plain, 8);
 	if (code)
-		goto out;
+		goto out_plain;
 
 	if ((plain[4] != plain[5]) || (plain[4] != plain[6])
 				   || (plain[4] != plain[7])) {
 		code = (s32)KG_BAD_SEQ;
-		goto out;
+		goto out_plain;
 	}
 
 	*direction = plain[4];
 
 	*seqnum = ((plain[0] << 24) | (plain[1] << 16) |
 					(plain[2] << 8) | (plain[3]));
+out_plain:
+	kfree(plain);
 out:
 	crypto_free_skcipher(cipher);
 	return code;
@@ -141,26 +161,33 @@
 	       int *direction, u32 *seqnum)
 {
 	s32 code;
-	unsigned char plain[8];
 	struct crypto_skcipher *key = kctx->seq;
+	unsigned char *plain;
 
 	dprintk("RPC:       krb5_get_seq_num:\n");
 
 	if (kctx->enctype == ENCTYPE_ARCFOUR_HMAC)
 		return krb5_get_rc4_seq_num(kctx, cksum, buf,
 					    direction, seqnum);
+	plain = kmalloc(8, GFP_NOFS);
+	if (!plain)
+		return -ENOMEM;
 
 	if ((code = krb5_decrypt(key, cksum, buf, plain, 8)))
-		return code;
+		goto out;
 
 	if ((plain[4] != plain[5]) || (plain[4] != plain[6]) ||
-	    (plain[4] != plain[7]))
-		return (s32)KG_BAD_SEQ;
+	    (plain[4] != plain[7])) {
+		code = (s32)KG_BAD_SEQ;
+		goto out;
+	}
 
 	*direction = plain[4];
 
 	*seqnum = ((plain[0]) |
 		   (plain[1] << 8) | (plain[2] << 16) | (plain[3] << 24));
 
-	return 0;
+out:
+	kfree(plain);
+	return code;
 }
-- 
1.8.3.1