From 3958b79266b14729edd61daf9dfb84de45f4ec6d Mon Sep 17 00:00:00 2001 From: Nicolas Iooss Date: Fri, 17 Jul 2015 16:23:45 -0700 Subject: configfs: fix kernel infoleak through user-controlled format string 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 Acked-by: Greg Kroah-Hartman Acked-by: Felipe Balbi Acked-by: Joel Becker Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/configfs/item.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'fs/configfs') 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); } -- cgit