environment: ignore env var assignments > 1 KiB (#2325)

...to guard against recursive constructs like FOO=$FOO:bar which would
grow on each reconfigure.

Add log message as well as a warning against this in the man page.

diff --git a/docs/labwc-config.5.scd b/docs/labwc-config.5.scd
index 636172e7e1c464c512364301c4383af822d468c4..66a8d61110754a30c7bbc4e524bb1d452ca1d53c 100644 (file)
--- a/docs/labwc-config.5.scd
+++ b/docs/labwc-config.5.scd
@@ -50,9 +50,14 @@ that directory contains either the "environment" file or at least one
 
 Note: environment files are treated differently by Openbox, which will simply
 source the file as a valid shell script before running the window manager. Files
-are instead parsed directly by labwc, although any environment variables
-referenced as $VARIABLE or ${VARIABLE} will be substituted and the tilde (~)
-will be expanded as the user's home directory.
+are instead parsed directly by labwc so that environment variables can be
+re-loaded on --reconfigure.
+
+Any environment variables referenced as $VARIABLE or ${VARIABLE} will be
+substituted and the tilde (~) will be expanded as the user's home directory.
+
+Please note that as labwc reloads the environment file(s) on reconfigure,
+recursive/circular assignments (for example FOO=$FOO:bar) should not be made.
 
 The *autostart* file is executed as a shell script after labwc has read its
 configuration and set variables defined in the environment file. Additionally,

diff --git a/src/config/session.c b/src/config/session.c
index c488c6b4540aab9f778df826c6d842763e6ec270..cfd0b4f4ab34fde1e695f8ecb39fd4132706ed65 100644 (file)
--- a/src/config/session.c
+++ b/src/config/session.c
@@ -33,6 +33,7 @@ static const char *const env_vars[] = {
        NULL
 };
 
+#define LAB_ENV_VAR_MAX_SIZE 1024
 static void
 process_line(char *line)
 {
@@ -52,12 +53,36 @@ process_line(char *line)
 
        struct buf value = BUF_INIT;
        buf_add(&value, string_strip(++p));
+
+       /*
+        * Users should not assign environment variables recursively (for
+        * example FOO=$FOO:bar) in the environment file because they would just
+        * keep growing on reconfigure. We could of course try to remember the
+        * original values, but it adds complexity for which we currently cannot
+        * see a use-case that could not easily be handled by some shell scripts
+        * separate from the environment file.
+        *
+        * Consequently we just check the size of the environment variables to
+        * defensively handle that growth issue in the case of inadvertent
+        * recursion.
+        */
+       if (value.len > LAB_ENV_VAR_MAX_SIZE) {
+               wlr_log(WLR_ERROR, "ignoring environment variable assignment as "
+                       "its size is greater than %d bytes which indicates recursion "
+                       "(%s=%s)", LAB_ENV_VAR_MAX_SIZE, key, value.data);
+               goto err;
+       }
+
        buf_expand_shell_variables(&value);
        buf_expand_tilde(&value);
        setenv(key, value.data, 1);
+
+err:
        buf_reset(&value);
 }
 
+#undef LAB_ENV_VAR_MAX_SIZE
+
 /* return true on successful read */
 static bool
 read_environment_file(const char *filename)