libceph: do not crash on large auth tickets

Large (greater than 32k, the value of PAGE_ALLOC_COSTLY_ORDER) auth
tickets will have their buffers vmalloc'ed, which leads to the
following crash in crypto:

[   28.685082] BUG: unable to handle kernel paging request at ffffeb04000032c0
[   28.686032] IP: [<ffffffff81392b42>] scatterwalk_pagedone+0x22/0x80
[   28.686032] PGD 0
[   28.688088] Oops: 0000 [#1] PREEMPT SMP
[   28.688088] Modules linked in:
[   28.688088] CPU: 0 PID: 878 Comm: kworker/0:2 Not tainted 3.17.0-vm+ #305
[   28.688088] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007
[   28.688088] Workqueue: ceph-msgr con_work
[   28.688088] task: ffff88011a7f9030 ti: ffff8800d903c000 task.ti: ffff8800d903c000
[   28.688088] RIP: 0010:[<ffffffff81392b42>]  [<ffffffff81392b42>] scatterwalk_pagedone+0x22/0x80
[   28.688088] RSP: 0018:ffff8800d903f688  EFLAGS: 00010286
[   28.688088] RAX: ffffeb04000032c0 RBX: ffff8800d903f718 RCX: ffffeb04000032c0
[   28.688088] RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff8800d903f750
[   28.688088] RBP: ffff8800d903f688 R08: 00000000000007de R09: ffff8800d903f880
[   28.688088] R10: 18df467c72d6257b R11: 0000000000000000 R12: 0000000000000010
[   28.688088] R13: ffff8800d903f750 R14: ffff8800d903f8a0 R15: 0000000000000000
[   28.688088] FS:  00007f50a41c7700(0000) GS:ffff88011fc00000(0000) knlGS:0000000000000000
[   28.688088] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[   28.688088] CR2: ffffeb04000032c0 CR3: 00000000da3f3000 CR4: 00000000000006b0
[   28.688088] Stack:
[   28.688088]  ffff8800d903f698 ffffffff81392ca8 ffff8800d903f6e8 ffffffff81395d32
[   28.688088]  ffff8800dac96000 ffff880000000000 ffff8800d903f980 ffff880119b7e020
[   28.688088]  ffff880119b7e010 0000000000000000 0000000000000010 0000000000000010
[   28.688088] Call Trace:
[   28.688088]  [<ffffffff81392ca8>] scatterwalk_done+0x38/0x40
[   28.688088]  [<ffffffff81392ca8>] scatterwalk_done+0x38/0x40
[   28.688088]  [<ffffffff81395d32>] blkcipher_walk_done+0x182/0x220
[   28.688088]  [<ffffffff813990bf>] crypto_cbc_encrypt+0x15f/0x180
[   28.688088]  [<ffffffff81399780>] ? crypto_aes_set_key+0x30/0x30
[   28.688088]  [<ffffffff8156c40c>] ceph_aes_encrypt2+0x29c/0x2e0
[   28.688088]  [<ffffffff8156d2a3>] ceph_encrypt2+0x93/0xb0
[   28.688088]  [<ffffffff8156d7da>] ceph_x_encrypt+0x4a/0x60
[   28.688088]  [<ffffffff8155b39d>] ? ceph_buffer_new+0x5d/0xf0
[   28.688088]  [<ffffffff8156e837>] ceph_x_build_authorizer.isra.6+0x297/0x360
[   28.688088]  [<ffffffff8112089b>] ? kmem_cache_alloc_trace+0x11b/0x1c0
[   28.688088]  [<ffffffff8156b496>] ? ceph_auth_create_authorizer+0x36/0x80
[   28.688088]  [<ffffffff8156ed83>] ceph_x_create_authorizer+0x63/0xd0
[   28.688088]  [<ffffffff8156b4b4>] ceph_auth_create_authorizer+0x54/0x80
[   28.688088]  [<ffffffff8155f7c0>] get_authorizer+0x80/0xd0
[   28.688088]  [<ffffffff81555a8b>] prepare_write_connect+0x18b/0x2b0
[   28.688088]  [<ffffffff81559289>] try_read+0x1e59/0x1f10

This is because we set up crypto scatterlists as if all buffers were
kmalloc'ed.  Fix it.

Cc: stable@vger.kernel.org
Signed-off-by: Ilya Dryomov <idryomov@redhat.com>
Reviewed-by: Sage Weil <sage@redhat.com>

net/ceph/crypto.c

@@ -90,11 +90,82 @@ static struct crypto_blkcipher *ceph_crypto_alloc_cipher(void)
 
 static const u8 *aes_iv = (u8 *)CEPH_AES_IV;
 
+/*
+ * Should be used for buffers allocated with ceph_kvmalloc().
+ * Currently these are encrypt out-buffer (ceph_buffer) and decrypt
+ * in-buffer (msg front).
+ *
+ * Dispose of @sgt with teardown_sgtable().
+ *
+ * @prealloc_sg is to avoid memory allocation inside sg_alloc_table()
+ * in cases where a single sg is sufficient.  No attempt to reduce the
+ * number of sgs by squeezing physically contiguous pages together is
+ * made though, for simplicity.
+ */
+static int setup_sgtable(struct sg_table *sgt, struct scatterlist *prealloc_sg,
+			 const void *buf, unsigned int buf_len)
+{
+	struct scatterlist *sg;
+	const bool is_vmalloc = is_vmalloc_addr(buf);
+	unsigned int off = offset_in_page(buf);
+	unsigned int chunk_cnt = 1;
+	unsigned int chunk_len = PAGE_ALIGN(off + buf_len);
+	int i;
+	int ret;
+
+	if (buf_len == 0) {
+		memset(sgt, 0, sizeof(*sgt));
+		return -EINVAL;
+	}
+
+	if (is_vmalloc) {
+		chunk_cnt = chunk_len >> PAGE_SHIFT;
+		chunk_len = PAGE_SIZE;
+	}
+
+	if (chunk_cnt > 1) {
+		ret = sg_alloc_table(sgt, chunk_cnt, GFP_NOFS);
+		if (ret)
+			return ret;
+	} else {
+		WARN_ON(chunk_cnt != 1);
+		sg_init_table(prealloc_sg, 1);
+		sgt->sgl = prealloc_sg;
+		sgt->nents = sgt->orig_nents = 1;
+	}
+
+	for_each_sg(sgt->sgl, sg, sgt->orig_nents, i) {
+		struct page *page;
+		unsigned int len = min(chunk_len - off, buf_len);
+
+		if (is_vmalloc)
+			page = vmalloc_to_page(buf);
+		else
+			page = virt_to_page(buf);
+
+		sg_set_page(sg, page, len, off);
+
+		off = 0;
+		buf += len;
+		buf_len -= len;
+	}
+	WARN_ON(buf_len != 0);
+
+	return 0;
+}
+
+static void teardown_sgtable(struct sg_table *sgt)
+{
+	if (sgt->orig_nents > 1)
+		sg_free_table(sgt);
+}
+
 static int ceph_aes_encrypt(const void *key, int key_len,
 			    void *dst, size_t *dst_len,
 			    const void *src, size_t src_len)
 {
-	struct scatterlist sg_in[2], sg_out[1];
+	struct scatterlist sg_in[2], prealloc_sg;
+	struct sg_table sg_out;
 	struct crypto_blkcipher *tfm = ceph_crypto_alloc_cipher();
 	struct blkcipher_desc desc = { .tfm = tfm, .flags = 0 };
 	int ret;
@@ -110,16 +181,18 @@ static int ceph_aes_encrypt(const void *key, int key_len,
 
 	*dst_len = src_len + zero_padding;
 
-	crypto_blkcipher_setkey((void *)tfm, key, key_len);
 	sg_init_table(sg_in, 2);
 	sg_set_buf(&sg_in[0], src, src_len);
 	sg_set_buf(&sg_in[1], pad, zero_padding);
-	sg_init_table(sg_out, 1);
-	sg_set_buf(sg_out, dst, *dst_len);
+	ret = setup_sgtable(&sg_out, &prealloc_sg, dst, *dst_len);
+	if (ret)
+		goto out_tfm;
+
+	crypto_blkcipher_setkey((void *)tfm, key, key_len);
 	iv = crypto_blkcipher_crt(tfm)->iv;
 	ivsize = crypto_blkcipher_ivsize(tfm);
-
 	memcpy(iv, aes_iv, ivsize);
+
 	/*
 	print_hex_dump(KERN_ERR, "enc key: ", DUMP_PREFIX_NONE, 16, 1,
 		       key, key_len, 1);
@@ -128,16 +201,22 @@ static int ceph_aes_encrypt(const void *key, int key_len,
 	print_hex_dump(KERN_ERR, "enc pad: ", DUMP_PREFIX_NONE, 16, 1,
 			pad, zero_padding, 1);
 	*/
-	ret = crypto_blkcipher_encrypt(&desc, sg_out, sg_in,
+	ret = crypto_blkcipher_encrypt(&desc, sg_out.sgl, sg_in,
 				     src_len + zero_padding);
-	crypto_free_blkcipher(tfm);
-	if (ret < 0)
+	if (ret < 0) {
 		pr_err("ceph_aes_crypt failed %d\n", ret);
+		goto out_sg;
+	}
 	/*
 	print_hex_dump(KERN_ERR, "enc out: ", DUMP_PREFIX_NONE, 16, 1,
 		       dst, *dst_len, 1);
 	*/
-	return 0;
+
+out_sg:
+	teardown_sgtable(&sg_out);
+out_tfm:
+	crypto_free_blkcipher(tfm);
+	return ret;
 }
 
 static int ceph_aes_encrypt2(const void *key, int key_len, void *dst,
@@ -145,7 +224,8 @@ static int ceph_aes_encrypt2(const void *key, int key_len, void *dst,
 			     const void *src1, size_t src1_len,
 			     const void *src2, size_t src2_len)
 {
-	struct scatterlist sg_in[3], sg_out[1];
+	struct scatterlist sg_in[3], prealloc_sg;
+	struct sg_table sg_out;
 	struct crypto_blkcipher *tfm = ceph_crypto_alloc_cipher();
 	struct blkcipher_desc desc = { .tfm = tfm, .flags = 0 };
 	int ret;
@@ -161,17 +241,19 @@ static int ceph_aes_encrypt2(const void *key, int key_len, void *dst,
 
 	*dst_len = src1_len + src2_len + zero_padding;
 
-	crypto_blkcipher_setkey((void *)tfm, key, key_len);
 	sg_init_table(sg_in, 3);
 	sg_set_buf(&sg_in[0], src1, src1_len);
 	sg_set_buf(&sg_in[1], src2, src2_len);
 	sg_set_buf(&sg_in[2], pad, zero_padding);
-	sg_init_table(sg_out, 1);
-	sg_set_buf(sg_out, dst, *dst_len);
+	ret = setup_sgtable(&sg_out, &prealloc_sg, dst, *dst_len);
+	if (ret)
+		goto out_tfm;
+
+	crypto_blkcipher_setkey((void *)tfm, key, key_len);
 	iv = crypto_blkcipher_crt(tfm)->iv;
 	ivsize = crypto_blkcipher_ivsize(tfm);
-
 	memcpy(iv, aes_iv, ivsize);
+
 	/*
 	print_hex_dump(KERN_ERR, "enc  key: ", DUMP_PREFIX_NONE, 16, 1,
 		       key, key_len, 1);
@@ -182,23 +264,30 @@ static int ceph_aes_encrypt2(const void *key, int key_len, void *dst,
 	print_hex_dump(KERN_ERR, "enc  pad: ", DUMP_PREFIX_NONE, 16, 1,
 			pad, zero_padding, 1);
 	*/
-	ret = crypto_blkcipher_encrypt(&desc, sg_out, sg_in,
+	ret = crypto_blkcipher_encrypt(&desc, sg_out.sgl, sg_in,
 				     src1_len + src2_len + zero_padding);
-	crypto_free_blkcipher(tfm);
-	if (ret < 0)
+	if (ret < 0) {
 		pr_err("ceph_aes_crypt2 failed %d\n", ret);
+		goto out_sg;
+	}
 	/*
 	print_hex_dump(KERN_ERR, "enc  out: ", DUMP_PREFIX_NONE, 16, 1,
 		       dst, *dst_len, 1);
 	*/
-	return 0;
+
+out_sg:
+	teardown_sgtable(&sg_out);
+out_tfm:
+	crypto_free_blkcipher(tfm);
+	return ret;
 }
 
 static int ceph_aes_decrypt(const void *key, int key_len,
 			    void *dst, size_t *dst_len,
 			    const void *src, size_t src_len)
 {
-	struct scatterlist sg_in[1], sg_out[2];
+	struct sg_table sg_in;
+	struct scatterlist sg_out[2], prealloc_sg;
 	struct crypto_blkcipher *tfm = ceph_crypto_alloc_cipher();
 	struct blkcipher_desc desc = { .tfm = tfm };
 	char pad[16];
@@ -210,16 +299,16 @@ static int ceph_aes_decrypt(const void *key, int key_len,
 	if (IS_ERR(tfm))
 		return PTR_ERR(tfm);
 
-	crypto_blkcipher_setkey((void *)tfm, key, key_len);
-	sg_init_table(sg_in, 1);
 	sg_init_table(sg_out, 2);
-	sg_set_buf(sg_in, src, src_len);
 	sg_set_buf(&sg_out[0], dst, *dst_len);
 	sg_set_buf(&sg_out[1], pad, sizeof(pad));
+	ret = setup_sgtable(&sg_in, &prealloc_sg, src, src_len);
+	if (ret)
+		goto out_tfm;
 
+	crypto_blkcipher_setkey((void *)tfm, key, key_len);
 	iv = crypto_blkcipher_crt(tfm)->iv;
 	ivsize = crypto_blkcipher_ivsize(tfm);
-
 	memcpy(iv, aes_iv, ivsize);
 
 	/*
@@ -228,12 +317,10 @@ static int ceph_aes_decrypt(const void *key, int key_len,
 	print_hex_dump(KERN_ERR, "dec  in: ", DUMP_PREFIX_NONE, 16, 1,
 		       src, src_len, 1);
 	*/
-
-	ret = crypto_blkcipher_decrypt(&desc, sg_out, sg_in, src_len);
-	crypto_free_blkcipher(tfm);
+	ret = crypto_blkcipher_decrypt(&desc, sg_out, sg_in.sgl, src_len);
 	if (ret < 0) {
 		pr_err("ceph_aes_decrypt failed %d\n", ret);
-		return ret;
+		goto out_sg;
 	}
 
 	if (src_len <= *dst_len)
@@ -251,7 +338,12 @@ static int ceph_aes_decrypt(const void *key, int key_len,
 	print_hex_dump(KERN_ERR, "dec out: ", DUMP_PREFIX_NONE, 16, 1,
 		       dst, *dst_len, 1);
 	*/
-	return 0;
+
+out_sg:
+	teardown_sgtable(&sg_in);
+out_tfm:
+	crypto_free_blkcipher(tfm);
+	return ret;
 }
 
 static int ceph_aes_decrypt2(const void *key, int key_len,
@@ -259,7 +351,8 @@ static int ceph_aes_decrypt2(const void *key, int key_len,
 			     void *dst2, size_t *dst2_len,
 			     const void *src, size_t src_len)
 {
-	struct scatterlist sg_in[1], sg_out[3];
+	struct sg_table sg_in;
+	struct scatterlist sg_out[3], prealloc_sg;
 	struct crypto_blkcipher *tfm = ceph_crypto_alloc_cipher();
 	struct blkcipher_desc desc = { .tfm = tfm };
 	char pad[16];
@@ -271,17 +364,17 @@ static int ceph_aes_decrypt2(const void *key, int key_len,
 	if (IS_ERR(tfm))
 		return PTR_ERR(tfm);
 
-	sg_init_table(sg_in, 1);
-	sg_set_buf(sg_in, src, src_len);
 	sg_init_table(sg_out, 3);
 	sg_set_buf(&sg_out[0], dst1, *dst1_len);
 	sg_set_buf(&sg_out[1], dst2, *dst2_len);
 	sg_set_buf(&sg_out[2], pad, sizeof(pad));
+	ret = setup_sgtable(&sg_in, &prealloc_sg, src, src_len);
+	if (ret)
+		goto out_tfm;
 
 	crypto_blkcipher_setkey((void *)tfm, key, key_len);
 	iv = crypto_blkcipher_crt(tfm)->iv;
 	ivsize = crypto_blkcipher_ivsize(tfm);
-
 	memcpy(iv, aes_iv, ivsize);
 
 	/*
@@ -290,12 +383,10 @@ static int ceph_aes_decrypt2(const void *key, int key_len,
 	print_hex_dump(KERN_ERR, "dec   in: ", DUMP_PREFIX_NONE, 16, 1,
 		       src, src_len, 1);
 	*/
-
-	ret = crypto_blkcipher_decrypt(&desc, sg_out, sg_in, src_len);
-	crypto_free_blkcipher(tfm);
+	ret = crypto_blkcipher_decrypt(&desc, sg_out, sg_in.sgl, src_len);
 	if (ret < 0) {
 		pr_err("ceph_aes_decrypt failed %d\n", ret);
-		return ret;
+		goto out_sg;
 	}
 
 	if (src_len <= *dst1_len)
@@ -325,7 +416,11 @@ static int ceph_aes_decrypt2(const void *key, int key_len,
 		       dst2, *dst2_len, 1);
 	*/
 
-	return 0;
+out_sg:
+	teardown_sgtable(&sg_in);
+out_tfm:
+	crypto_free_blkcipher(tfm);
+	return ret;
 }