swapon: do not run execvp() calls when swapon is setuid binary

swapon(8) is not expected to be setuid binary, but if it is try to avoid
obvious security vulnerability of executing user preferred mkswap file as
someone else, such as root.

Signed-off-by: Sami Kerola <kerolasa@iki.fi>

diff --git a/sys-utils/swapon.c b/sys-utils/swapon.c
index 5ad5cd1f3b6a835e06024d4d77a2d6199077e3f8..be8f7718bbf1f34f55eb700603eeeeccf4fc1669 100644 (file)
--- a/sys-utils/swapon.c
+++ b/sys-utils/swapon.c
@@ -297,6 +297,10 @@ static int swap_reinitialize(struct swapon_ctl *ctl)
        char const *cmd[7];
        int idx=0;
 
+       if (geteuid() != getuid()) {
+               warnx(_("will not execute mkswap when swapon is setuid binary"));
+               return -1;
+       }
        warnx(_("%s: reinitializing the swap."), ctl->device);
 
        switch((pid=fork())) {