From af49b10669467685a03ca860dd9d7c5fc3a590b5 Mon Sep 17 00:00:00 2001
From: Nathan Wagner <nw@hydaspes.if.org>
Date: Sun, 28 Oct 2018 16:25:25 +0000
Subject: [PATCH] fix readlink bug in syncfs

---
 zpm-syncfs.c | 39 ++++++++++++++++++++++++++++++++++++---
 1 file changed, 36 insertions(+), 3 deletions(-)

diff --git a/zpm-syncfs.c b/zpm-syncfs.c
index ecc66c8..ff80041 100644
--- a/zpm-syncfs.c
+++ b/zpm-syncfs.c
@@ -334,19 +334,35 @@ static int remove_files(void *f, int ncols, char **vals, char **cols) {
 
 #define MARK fprintf(stderr, "%s %d: mark\n", __func__, __LINE__)
 
+/* file does not exist */
 #define D_NOEXIST 0x1
+/* files are different types */
 #define D_TYPE 0x2
+/* metadata is different */
 #define D_MD 0x4
+/* content or link target is different */
 #define D_HASH 0x8
+/* file to be installed is a directory */
 #define D_ISDIR  0x10
+/* path on disk is a directory */
 #define D_EISDIR 0x20
+/* usernames different */
 #define D_UID 0x40
+/* group names different */
 #define D_GID 0x80
+/* file mode is different */
 #define D_MODE 0x100
+/* mtimes are different */
 #define D_MTIME 0x200
+/* the hash of the file we are supposedly replacing is different than
+ * the the hash of the file on disk
+ */
 #define D_OHASH 0x400
+/* an error occurred trying to compare the file (other than it doesn't exist */
 #define D_ERROR 0x1000
+/* there was a stat error */
 #define D_STATERROR 0x2000
+/* there was an error calling readlink */
 #define D_RLERROR 0x4000
 
 /* 1 = file doesn't exist, 2 = file is a directory, target isn't */
@@ -388,11 +404,15 @@ static unsigned int file_compare(struct nitem *n, struct stat *st) {
 		}
 		if (n->hash && etype == S_IFLNK && stat_type == S_IFLNK) {
 			lsize = readlink(n->dest, link, sizeof link);
+
 			if (lsize == -1 || lsize == sizeof link) {
 				diff |= D_RLERROR;
 				diff |= D_ERROR;
-			} else if (strcmp(n->target, link) != 0) {
-				diff |= D_HASH;
+			} else {
+				link[lsize] = 0;
+				if (strcmp(n->target, link) != 0) {
+					diff |= D_HASH;
+				}
 			}
 		}
 		if (n->uid != st->st_uid) {
@@ -956,7 +976,20 @@ static int install_files(void *f, int ncols, char **vals, char **cols) {
 				/* accept doesn't matter, since it's
 				 * not an acceptable file */
 				/* error */
-				return seterror(conf, "%s (hashdiff): %s", accept ? "existing file not acceptable" : "file exists", nitem.dest);
+				if (nitem.ftype == 'l') {
+					char link[1024];
+					ssize_t lsize;
+					lsize = readlink(nitem.dest, link, sizeof link);
+					if (lsize == -1 || (size_t)lsize >= sizeof link) {
+						return seterror(conf, "%s (linkdiff): expecting %s -> %s, unable to read link", accept ? "existing file not acceptable" : "file exists", nitem.dest, nitem.target, link);
+					} else {
+						link[lsize] = 0;
+						/* links must be different */
+						return seterror(conf, "%s (linkdiff): expecting %s -> %s, have -> %s", accept ? "existing file not acceptable" : "file exists", nitem.dest, nitem.target, link);
+					}
+				} else {
+					return seterror(conf, "%s (hashdiff): %s", accept ? "existing file not acceptable" : "file exists", nitem.dest);
+				}
 			}
 			if (!mdsame && hashsame && overwrite) {
 				/* fix md */
-- 
2.40.0