base-files: sysupgrade: quote source image name

get_image() eval a filename without quoting it, resulting in errors with
filenames containing characters that need to be escaped.
    $ sysupgrade -T -f ./cfg\(12\).tar.gz img.bin; echo $?
    Image check 'platform_check_image' failed.
    Invalid config file. Please use only .tar.gz files
    1
    $ mv cfg\(12\).tar.gz cfg_12.tar.gz
    $ mv img\(1\).bin img.bin
    sysupgrade -T -f ./cfg_12.tar.gz img.bin; echo $?
    0

Enclose the content of $from in double quotes.

Signed-off-by: Adrien Schildknecht <adrien+dev@schischi.me>

SVN-Revision: 46919

package/base-files/files/lib/upgrade/common.sh

@@ -184,14 +184,14 @@ get_image() { # <source> [ <command> ]
 		*) cmd="cat";;
 	esac
 	if [ -z "$conc" ]; then
-		local magic="$(eval $cmd $from 2>/dev/null | dd bs=2 count=1 2>/dev/null | hexdump -n 2 -e '1/1 "%02x"')"
+		local magic="$(eval $cmd \"$from\" 2>/dev/null | dd bs=2 count=1 2>/dev/null | hexdump -n 2 -e '1/1 "%02x"')"
 		case "$magic" in
 			1f8b) conc="zcat";;
 			425a) conc="bzcat";;
 		esac
 	fi
 
-	eval "$cmd $from 2>/dev/null ${conc:+| $conc}"
+	eval "$cmd \"$from\" 2>/dev/null ${conc:+| $conc}"
 }
 
 get_magic_word() {