diff options
authorNicolas Iooss <nicolas.iooss_linux@m4x.org>2015-07-17 16:23:45 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-07-17 16:39:53 -0700
commit3958b79266b14729edd61daf9dfb84de45f4ec6d (patch)
parent8db1486065141e619e4855b84e350ef32064f7e1 (diff)
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 <nicolas.iooss_linux@m4x.org> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Acked-by: Felipe Balbi <balbi@ti.com> Acked-by: Joel Becker <jlbec@evilplan.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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);
if (ret) {
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;
@@ -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;