e2p: fix segfault in e2p_os2string

Passing in a negative integer would lead to a segfault, and
a crafted filesystem image could trigger that.

Signed-off-by: Adam Buchbinder <abuchbinder@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/lib/e2p/ostype.c b/lib/e2p/ostype.c
index 7f08844..c5fd8ab 100644 (file)
--- a/lib/e2p/ostype.c
+++ b/lib/e2p/ostype.c
@@ -30,7 +30,7 @@ char *e2p_os2string(int os_type)
         const char     *os;
        char            *ret;
 
-       if (os_type <= EXT2_OS_LITES)
+       if (os_type >= 0 && os_type <= EXT2_OS_LITES)
                os = os_tab[os_type];
        else
                os = "(unknown os)";