pppd: Make sure word read from options file is null-terminated

If a word read from an options file was longer than MAXWORDLEN,
we could pass it to option_error() without null termination,
which could have lead to an out-of-bounds access in vslprintf.
Make sure word[] is null terminated in all cases.

Reported-by: Florian Kohnhäuser <florian@kohnhaeuser.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

diff --git a/pppd/options.c b/pppd/options.c
index 5e1489f495779d9e58a481f5177ecda66c9166b5..f1d2dc9ddf36947df03d864c47241a6bb34def32 100644 (file)
--- a/pppd/options.c
+++ b/pppd/options.c
@@ -1357,6 +1357,7 @@ getword(f, word, newlinep, filename)
 
        c = getc(f);
     }
+    word[MAXWORDLEN-1] = 0;    /* make sure word is null-terminated */
 
     /*
      * End of the word: check for errors.