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(-) > > diff --git a/drivers/usb/gadget/configfs.c b/drivers/usb/gadget/configfs.c > index 0495c94a23d7..289e20119fea 100644 > --- a/drivers/usb/gadget/configfs.c > +++ b/drivers/usb/gadget/configfs.c > @@ -571,7 +571,7 @@ static struct config_group *function_make( > if (IS_ERR(fi)) > return ERR_CAST(fi); > > - ret = config_item_set_name(&fi->group.cg_item, name); > + ret = config_item_set_name(&fi->group.cg_item, "%s", name);
No objections from me: Acked-by: Felipe Balbi <[email protected]> > if (ret) { > usb_put_function_instance(fi); > return ERR_PTR(ret); > diff --git a/fs/configfs/item.c b/fs/configfs/item.c > index 4d6a30e76168..b863a09cd2f1 100644 > --- a/fs/configfs/item.c > +++ b/fs/configfs/item.c > @@ -115,7 +115,7 @@ void config_item_init_type_name(struct config_item *item, > const char *name, > struct config_item_type *type) > { > - config_item_set_name(item, name); > + config_item_set_name(item, "%s", name); > item->ci_type = type; > config_item_init(item); > } > @@ -124,7 +124,7 @@ EXPORT_SYMBOL(config_item_init_type_name); > void config_group_init_type_name(struct config_group *group, const char > *name, > struct config_item_type *type) > { > - config_item_set_name(&group->cg_item, name); > + config_item_set_name(&group->cg_item, "%s", name); > group->cg_item.ci_type = type; > config_group_init(group); > } > -- > 2.4.5 > -- balbi
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