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" --- arch/ia64/kernel/perfmon.c | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/ia64') diff --git a/arch/ia64/kernel/perfmon.c b/arch/ia64/kernel/perfmon.c index 433f5e8a2cd1..2eda28414abb 100644 --- a/arch/ia64/kernel/perfmon.c +++ b/arch/ia64/kernel/perfmon.c @@ -619,6 +619,7 @@ static struct file_system_type pfm_fs_type = { .mount = pfmfs_mount, .kill_sb = kill_anon_super, }; +MODULE_ALIAS_FS("pfmfs"); DEFINE_PER_CPU(unsigned long, pfm_syst_info); DEFINE_PER_CPU(struct task_struct *, pmu_owner); -- cgit v1.2.2 From 4febd95a8a85dd38b1a71fcf9726e19c7fd20039 Mon Sep 17 00:00:00 2001 From: Stephen Rothwell Date: Thu, 7 Mar 2013 15:48:16 +1100 Subject: Select VIRT_TO_BUS directly where needed In commit 887cbce0adea ("arch Kconfig: centralise ARCH_NO_VIRT_TO_BUS") I introduced the config sybmol HAVE_VIRT_TO_BUS and selected that where needed. I am not sure what I was thinking. Instead, just directly select VIRT_TO_BUS where it is needed. Signed-off-by: Stephen Rothwell Signed-off-by: Linus Torvalds --- arch/ia64/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/ia64') diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig index 33f3fdc0b214..9a02f71c6b1f 100644 --- a/arch/ia64/Kconfig +++ b/arch/ia64/Kconfig @@ -26,7 +26,7 @@ config IA64 select HAVE_MEMBLOCK select HAVE_MEMBLOCK_NODE_MAP select HAVE_VIRT_CPU_ACCOUNTING - select HAVE_VIRT_TO_BUS + select VIRT_TO_BUS select ARCH_DISCARD_MEMBLOCK select GENERIC_IRQ_PROBE select GENERIC_PENDING_IRQ if SMP -- cgit v1.2.2