[RFC PATCH 15/35] syscalls: do not call sys_umount() within the kernel

From: Dominik Brodowski
Date: Sun Mar 11 2018 - 07:00:16 EST


CC: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx>
---
fs/namespace.c | 9 +++++++--
include/linux/syscalls.h | 1 +
init/do_mounts_initrd.c | 2 +-
3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index 642b8b229944..e398f32d7541 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1680,7 +1680,7 @@ static inline bool may_mandlock(void)
* unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
*/

-SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
+int ksys_umount(char __user *name, int flags)
{
struct path path;
struct mount *mnt;
@@ -1720,6 +1720,11 @@ SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
return retval;
}

+SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
+{
+ return ksys_umount(name, flags);
+}
+
#ifdef __ARCH_WANT_SYS_OLDUMOUNT

/*
@@ -1727,7 +1732,7 @@ SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
*/
SYSCALL_DEFINE1(oldumount, char __user *, name)
{
- return sys_umount(name, 0);
+ return ksys_umount(name, 0);
}

#endif
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 63625d2cbcb8..d509f4992d2e 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -950,5 +950,6 @@ asmlinkage long sys_statx(int dfd, const char __user *path, unsigned flags,

int ksys_mount(char __user *dev_name, char __user *dir_name, char __user *type,
unsigned long flags, void __user *data);
+int ksys_umount(char __user *name, int flags);

#endif
diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c
index 7868a6039fb4..1c4da8353332 100644
--- a/init/do_mounts_initrd.c
+++ b/init/do_mounts_initrd.c
@@ -105,7 +105,7 @@ static void __init handle_initrd(void)
else
printk("failed\n");
printk(KERN_NOTICE "Unmounting old root\n");
- sys_umount("/old", MNT_DETACH);
+ ksys_umount("/old", MNT_DETACH);
printk(KERN_NOTICE "Trying to free ramdisk memory ... ");
if (fd < 0) {
error = fd;
--
2.16.2