submodule foreach: skip eval for more than one argument

'eval "$@"' creates an extra layer of shell interpretation, which is
probably not expected by a user who passes multiple arguments to git
submodule foreach:

 $ git grep "'"
 [searches for single quotes]
 $ git submodule foreach git grep "'"
 Entering '[submodule]'
 /usr/lib/git-core/git-submodule: 1: eval: Syntax error: Unterminated quoted string
 Stopping at '[submodule]'; script returned non-zero status.

To fix this, if the user passes more than one argument, execute "$@"
directly instead of passing it to eval.

Examples:

 * Typical usage when adding an extra level of quoting is to pass a
   single argument representing the entire command to be passed to the
   shell.  This doesn't change that.

 * One can imagine someone feeding untrusted input as an argument:

 	git submodule foreach git grep "$variable"

   That currently results in a nonobvious shell code injection
   vulnerability.  Executing the command named by the arguments
   directly, as in this patch, fixes it.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>
Acked-by: Johan Herland <johan@herland.net>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/t/t7407-submodule-foreach.sh b/t/t7407-submodule-foreach.sh
index be93f10cf..6b2fd39aa 100755
--- a/t/t7407-submodule-foreach.sh
+++ b/t/t7407-submodule-foreach.sh
@@ -329,4 +329,13 @@ test_expect_success 'command passed to foreach --recursive retains notion of std
 	test_cmp expected actual
 '
 
+test_expect_success 'multi-argument command passed to foreach is not shell-evaluated twice' '
+	(
+		cd super &&
+		git submodule foreach "echo \\\"quoted\\\"" > ../expected &&
+		git submodule foreach echo \"quoted\" > ../actual
+	) &&
+	test_cmp expected actual
+'
+
 test_done