From 7f78e0351394052e1a6293e175825eb5c7869507 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Sat, 2 Mar 2013 19:39:14 -0800 Subject: fs: Limit sys_mount to only request filesystem modules. Modify the request_module to prefix the file system type with "fs-" and add aliases to all of the filesystems that can be built as modules to match. A common practice is to build all of the kernel code and leave code that is not commonly needed as modules, with the result that many users are exposed to any bug anywhere in the kernel. Looking for filesystems with a fs- prefix limits the pool of possible modules that can be loaded by mount to just filesystems trivially making things safer with no real cost. Using aliases means user space can control the policy of which filesystem modules are auto-loaded by editing /etc/modprobe.d/*.conf with blacklist and alias directives. Allowing simple, safe, well understood work-arounds to known problematic software. This also addresses a rare but unfortunate problem where the filesystem name is not the same as it's module name and module auto-loading would not work. While writing this patch I saw a handful of such cases. The most significant being autofs that lives in the module autofs4. This is relevant to user namespaces because we can reach the request module in get_fs_type() without having any special permissions, and people get uncomfortable when a user specified string (in this case the filesystem type) goes all of the way to request_module. After having looked at this issue I don't think there is any particular reason to perform any filtering or permission checks beyond making it clear in the module request that we want a filesystem module. The common pattern in the kernel is to call request_module() without regards to the users permissions. In general all a filesystem module does once loaded is call register_filesystem() and go to sleep. Which means there is not much attack surface exposed by loading a filesytem module unless the filesystem is mounted. In a user namespace filesystems are not mounted unless .fs_flags = FS_USERNS_MOUNT, which most filesystems do not set today. Acked-by: Serge Hallyn Acked-by: Kees Cook Reported-by: Kees Cook Signed-off-by: "Eric W. Biederman" --- drivers/usb/gadget/f_fs.c | 1 + drivers/usb/gadget/inode.c | 1 + 2 files changed, 2 insertions(+) (limited to 'drivers/usb') diff --git a/drivers/usb/gadget/f_fs.c b/drivers/usb/gadget/f_fs.c index 38388d7844fc..c377ff84bf2c 100644 --- a/drivers/usb/gadget/f_fs.c +++ b/drivers/usb/gadget/f_fs.c @@ -1235,6 +1235,7 @@ static struct file_system_type ffs_fs_type = { .mount = ffs_fs_mount, .kill_sb = ffs_fs_kill_sb, }; +MODULE_ALIAS_FS("functionfs"); /* Driver's main init/cleanup functions *************************************/ diff --git a/drivers/usb/gadget/inode.c b/drivers/usb/gadget/inode.c index 8ac840f25ba9..e2b2e9cf254a 100644 --- a/drivers/usb/gadget/inode.c +++ b/drivers/usb/gadget/inode.c @@ -2105,6 +2105,7 @@ static struct file_system_type gadgetfs_type = { .mount = gadgetfs_mount, .kill_sb = gadgetfs_kill_sb, }; +MODULE_ALIAS_FS("gadgetfs"); /*----------------------------------------------------------------------*/ -- cgit From 53540098b23c3884b4a0b4f220b9d977bc496af3 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Sun, 3 Mar 2013 22:35:20 +0100 Subject: ACPI / glue: Add .match() callback to struct acpi_bus_type USB uses the .find_bridge() callback from struct acpi_bus_type incorrectly, because as a result of the way it is used by USB every device in the system that doesn't have a bus type or parent is passed to usb_acpi_find_device() for inspection. What USB actually needs, though, is to call usb_acpi_find_device() for USB ports that don't have a bus type defined, but have usb_port_device_type as their device type, as well as for USB devices. To fix that replace the struct bus_type pointer in struct acpi_bus_type used for matching devices to specific subsystems with a .match() callback to be used for this purpose and update the users of struct acpi_bus_type, including USB, accordingly. Define the .match() callback routine for USB, usb_acpi_bus_match(), in such a way that it will cover both USB devices and USB ports and remove the now redundant .find_bridge() callback pointer from usb_acpi_bus. Signed-off-by: Rafael J. Wysocki Acked-by: Greg Kroah-Hartman Acked-by: Yinghai Lu Acked-by: Jeff Garzik --- drivers/usb/core/usb-acpi.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'drivers/usb') diff --git a/drivers/usb/core/usb-acpi.c b/drivers/usb/core/usb-acpi.c index cef4252bb31a..b6f4bad3f756 100644 --- a/drivers/usb/core/usb-acpi.c +++ b/drivers/usb/core/usb-acpi.c @@ -210,9 +210,14 @@ static int usb_acpi_find_device(struct device *dev, acpi_handle *handle) return 0; } +static bool usb_acpi_bus_match(struct device *dev) +{ + return is_usb_device(dev) || is_usb_port(dev); +} + static struct acpi_bus_type usb_acpi_bus = { - .bus = &usb_bus_type, - .find_bridge = usb_acpi_find_device, + .name = "USB", + .match = usb_acpi_bus_match, .find_device = usb_acpi_find_device, }; -- cgit