MFC: r291091

install: do not follow symlinks

In case the target of install is a dead symlink, install(1) used to not
consider it as "existing" because of the usage of stat(2) instead of
lstat(2).  meaning the old file (the symlink) is not removed before the new
file is created. The symlink is being followed and the new file becoming the
target of the symlink instead of the target of install(1)

Reviewed by:	jhb, brooks
Differential Revision:	https://reviews.freebsd.org/D4191

1 files changed, 5 insertions, 11 deletions

diff --git a/usr.bin/xinstall/xinstall.c b/usr.bin/xinstall/xinstall.c
index 15b115a..ae2ab79 100644
--- a/usr.bin/xinstall/xinstall.c
+++ b/usr.bin/xinstall/xinstall.c
@@ -748,10 +748,7 @@ install(const char *from_name, const char *to_name, u_long fset, u_int flags)
 		devnull = 1;
 	}
 
-	if (!dolink)
-		target = (stat(to_name, &to_sb) == 0);
-	else
-		target = (lstat(to_name, &to_sb) == 0);
+	target = (lstat(to_name, &to_sb) == 0);
 
 	if (dolink) {
 		if (target && !safecopy) {
@@ -766,8 +763,7 @@ install(const char *from_name, const char *to_name, u_long fset, u_int flags)
 		return;
 	}
 
-	/* Only install to regular files. */
-	if (target && !S_ISREG(to_sb.st_mode)) {
+	if (target && !S_ISREG(to_sb.st_mode) && !S_ISLNK(to_sb.st_mode)) {
 		errno = EFTYPE;
 		warn("%s", to_name);
 		return;
@@ -780,7 +776,7 @@ install(const char *from_name, const char *to_name, u_long fset, u_int flags)
 		err(EX_OSERR, "%s", from_name);
 
 	/* If we don't strip, we can compare first. */
-	if (docompare && !dostrip && target) {
+	if (docompare && !dostrip && target && S_ISREG(to_sb.st_mode)) {
 		if ((to_fd = open(to_name, O_RDONLY, 0)) < 0)
 			err(EX_OSERR, "%s", to_name);
 		if (devnull)
@@ -832,7 +828,7 @@ install(const char *from_name, const char *to_name, u_long fset, u_int flags)
 	/*
 	 * Compare the stripped temp file with the target.
 	 */
-	if (docompare && dostrip && target) {
+	if (docompare && dostrip && target && S_ISREG(to_sb.st_mode)) {
 		temp_fd = to_fd;
 
 		/* Re-open to_fd using the real target name. */
@@ -866,9 +862,7 @@ install(const char *from_name, const char *to_name, u_long fset, u_int flags)
 			}
 			(void) close(temp_fd);
 		}
-	}
-
-	if (dostrip && (!docompare || !target))
+	} else if (dostrip)
 		digestresult = digest_file(tempfile);
 
 	/*