On Tue, Jul 07, 2015 at 10:28:00PM +0800, Nicolas Iooss wrote: > Some modules call config_item_init_type_name() and > config_group_init_type_name() with parameter "name" directly controlled > by userspace. These two functions call config_item_set_name() with this > name used as a format string, which can be used to leak information such > as content of the stack to userspace. > > For example, make_netconsole_target() in netconsole module calls > config_item_init_type_name() with the name of a newly-created directory. > This means that the following commands give some unexpected output, with > configfs mounted in /sys/kernel/config/ and on a system with a > configured eth0 ethernet interface: > > # modprobe netconsole > # mkdir /sys/kernel/config/netconsole/target_%lx > # echo eth0 > /sys/kernel/config/netconsole/target_%lx/dev_name > # echo 1 > /sys/kernel/config/netconsole/target_%lx/enabled > # echo eth0 > /sys/kernel/config/netconsole/target_%lx/dev_name > # dmesg |tail -n1 > [ 142.697668] netconsole: target (target_ffffffffc0ae8080) is > enabled, disable to update parameters > > The directory name is correct but %lx has been interpreted in the > internal item name, displayed here in the error message used by > store_dev_name() in drivers/net/netconsole.c. > > To fix this, update every caller of config_item_set_name to use "%s" > when operating on untrusted input. > > This issue was found using -Wformat-security gcc flag, once a __printf > attribute has been added to config_item_set_name(). > > Signed-off-by: Nicolas Iooss <[email protected]> > --- > drivers/usb/gadget/configfs.c | 2 +- > fs/configfs/item.c | 4 ++-- > 2 files changed, 3 insertions(+), 3 deletions(-)
Nice catch: Acked-by: Greg Kroah-Hartman <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
