From: Ralph Boehme <slow@samba.org>
Date: Fri, 25 Oct 2019 13:21:32 +0000 (+0200)
Subject: lib/adouble: drop ad_data reallocate logic
X-Git-Tag: talloc-2.3.1~206
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9a3da6bebcdb924ca2027337544d79ac2088677e;p=thirdparty%2Fsamba.git

lib/adouble: drop ad_data reallocate logic

Simply set the buffer size to AD_XATTR_MAX_HDR_SIZE. When reading the
AppleDouble file, read up to AD_XATTR_MAX_HDR_SIZE from the file.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14171

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
---

diff --git a/source3/lib/adouble.c b/source3/lib/adouble.c
index ff3ba0dc48a..49ab8865d6a 100644
--- a/source3/lib/adouble.c
+++ b/source3/lib/adouble.c
@@ -2151,8 +2151,7 @@ static ssize_t ad_read_rsrc_adouble(vfs_handle_struct *handle,
 				    struct adouble *ad,
 				    const struct smb_filename *smb_fname)
 {
-	char *p_ad = NULL;
-	size_t size;
+	size_t to_read;
 	ssize_t len;
 	int ret;
 	bool ok;
@@ -2164,32 +2163,17 @@ static ssize_t ad_read_rsrc_adouble(vfs_handle_struct *handle,
 		return -1;
 	}
 
-	/*
-	 * AppleDouble file header content and size, two cases:
-	 *
-	 * - without xattrs it is exactly AD_DATASZ_DOT_UND (82) bytes large
-	 * - with embedded xattrs it can be larger, up to AD_XATTR_MAX_HDR_SIZE
-	 *
-	 * Read as much as we can up to AD_XATTR_MAX_HDR_SIZE.
-	 */
-	size = ad->ad_fsp->fsp_name->st.st_ex_size;
-	if (size > talloc_array_length(ad->ad_data)) {
-		if (size > AD_XATTR_MAX_HDR_SIZE) {
-			size = AD_XATTR_MAX_HDR_SIZE;
-		}
-		p_ad = talloc_realloc(ad, ad->ad_data, char, size);
-		if (p_ad == NULL) {
-			return -1;
-		}
-		ad->ad_data = p_ad;
+	to_read = ad->ad_fsp->fsp_name->st.st_ex_size;
+	if (to_read > AD_XATTR_MAX_HDR_SIZE) {
+		to_read = AD_XATTR_MAX_HDR_SIZE;
 	}
 
 	len = SMB_VFS_NEXT_PREAD(handle,
 				 ad->ad_fsp,
 				 ad->ad_data,
-				 talloc_array_length(ad->ad_data),
+				 to_read,
 				 0);
-	if (len != talloc_array_length(ad->ad_data)) {
+	if (len != to_read)  {
 		DBG_NOTICE("%s %s: bad size: %zd\n",
 			   smb_fname->base_name, strerror(errno), len);
 		return -1;
@@ -2287,7 +2271,23 @@ static struct adouble *ad_alloc(TALLOC_CTX *ctx,
 		adsize = AD_DATASZ_XATTR;
 		break;
 	case ADOUBLE_RSRC:
-		adsize = AD_DATASZ_DOT_UND;
+		/*
+		 * AppleDouble ._ file case, optimize for fewer (but larger)
+		 * IOs. Two cases:
+		 *
+		 * - without xattrs size of the header is exactly
+		 *   AD_DATASZ_DOT_UND (82) bytes
+		 *
+		 * - with embedded xattrs it can be larger, up to
+		 *   AD_XATTR_MAX_HDR_SIZE
+		 *
+		 * Larger headers are not supported, but this is a reasonable
+		 * limit that is also employed by the macOS client.
+		 *
+		 * We used the largest possible size to be able to read the full
+		 * header with one IO.
+		 */
+		adsize = AD_XATTR_MAX_HDR_SIZE;
 		break;
 	default:
 		return NULL;