utils-std

commit: 3222081dd068d490c610c2f79797d6f53374a862
parent 08147ec21ddca45950d806e72ebfba30f44dc3c3
Author: Haelwenn (lanodan) Monnier <contact@hacktivis.me>
Date:   Sat, 13 Dec 2025 16:29:53 +0100

cmd/ln: Don't skip directory check prior to unlinking with -T

Done because unlink() returning EISDIR is a Linux extension,
and EPERM (BSD, POSIX.1-2024) is too generic an error.

Smells like a TOCTOU trap to me but it is what it is…

Diffstat:
M
cmd/ln.c
10
++++++++--
M
test-cmd/ln.sh
4
++--

2 files changed, 10 insertions(+), 4 deletions(-)
diff --git a/cmd/ln.c b/cmd/ln.c
@@ -68,7 +68,7 @@ do_link(char *src, char *dest, int destfd)
 		return -1;
 	}
 
-	if(destfd < 0 && !opt_T)
+	if(destfd < 0)
 	{
 		destfd = open(dest, open_dest_flags);
 		if(destfd < 0)
@@ -95,8 +95,14 @@ do_link(char *src, char *dest, int destfd)
 	}
 
 	int dirfd = AT_FDCWD;
-	if(S_ISDIR(dest_stat.st_mode) && !opt_T)
+	if(S_ISDIR(dest_stat.st_mode))
 	{
+		if(opt_T)
+		{
+			fprintf(stderr, "ln: error: Option -T passed but target '%s' is a directory\n", dest);
+			return -1;
+		}
+
 		dirfd = destfd;
 	}
 	else
diff --git a/test-cmd/ln.sh b/test-cmd/ln.sh
@@ -126,7 +126,7 @@ t_cmd Ts:cleanup '' rm Ts
 t_cmd Ts.d:mkdir '' mkdir -p Ts.d
 t_args --exit=1 Ts.d "ln: error: Destination 'Ts.d' already exists
 " -Ts / Ts.d
-t_args --exit=1 Ts.d:f "ln: error: Failed unlinking destination 'Ts.d': Is a directory
+t_args --exit=1 Ts.d:f "ln: error: Option -T passed but target 'Ts.d' is a directory
 " -Tsf / Ts.d
 t_cmd Ts.d:rmdir '' rm -r Ts.d
 
@@ -139,6 +139,6 @@ t_cmd T.d:mkdir '' mkdir -p T.d
 t_args --exit=1 T.d "ln: error: Destination 'T.d' already exists
 " -T "$target" T.d
 t_cmd '' '' test -d T.d
-t_args --exit=1 T.d:f "ln: error: Failed unlinking destination 'T.d': Is a directory
+t_args --exit=1 T.d:f "ln: error: Option -T passed but target 'T.d' is a directory
 " -Tf "$target" T.d
 t_cmd T.d:rmdir '' rm -r T.d