Fix executable file ownership check

If we check ownership for a file we find in
the system PATH then we might need a .exe suffix
on the full path we identified, because although
MSYS will confirm the files existence even if the
suffix is missing, we need the "correct" path
for the actual ownership check.

src/pacman/query.c

@@ -61,7 +61,10 @@ static int search_path(char **filename, struct stat *bufptr)
 			path[--plen] = '\0';
 		}
 
-		fullname = malloc(plen + flen + 2);
+		/* Reserve 4 additional bytes for a potential ".exe" extension
+		 * This is not always needed, but avoids reallocation.
+		 */
+		fullname = malloc(plen + 1 + flen + 4 + 1);
 		if(!fullname) {
 			free(envpath);
 			return -1;
@@ -70,6 +73,32 @@ static int search_path(char **filename, struct stat *bufptr)
 
 		if(lstat(fullname, bufptr) == 0) {
 			free(*filename);
+
+			/* We check if the file actually has an .exe suffix by lstat'ing
+			 * the same path with .exe suffix and checking if the inode
+			 * numbers are the same: If they are, we return the name with
+			 * .exe appended, because otherwise the package ownership check
+			 * breaks/fails.
+			 */
+			strcat(fullname, ".exe");
+			struct stat sbExe;
+			if (lstat(fullname, &sbExe) == 0) {
+				if (sbExe.st_ino == bufptr->st_ino) {
+					/* file is the same with and without .exe suffix
+					 * => we assume that the .exe suffix is needed for the
+					 * ownership check.
+					 */
+					*filename = fullname;
+					*bufptr = sbExe;
+					free(envpath);
+					return 0;
+				}
+			}
+			/* undo the .exe suffix, because there is no such file or it's
+			 * different from the one without .exe suffix.
+			 */
+			fullname[plen + 1 + flen] = '\0';
+
 			*filename = fullname;
 			free(envpath);
 			return 0;