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Subject[PATCH 3.2 022/104] fs: namespace: suppress 'may be used uninitialized' warnings
3.2.101-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Tim Gardner <tim.gardner@canonical.com>

commit b8850d1fa8e2f6653e57daf6d08e58c5f5eb2c85 upstream.

The gcc version 4.9.1 compiler complains Even though it isn't possible for
these variables to not get initialized before they are used.

fs/namespace.c: In function ‘SyS_mount’:
fs/namespace.c:2720:8: warning: ‘kernel_dev’ may be used uninitialized in this function [-Wmaybe-uninitialized]
ret = do_mount(kernel_dev, kernel_dir->name, kernel_type, flags,
^
fs/namespace.c:2699:8: note: ‘kernel_dev’ was declared here
char *kernel_dev;
^
fs/namespace.c:2720:8: warning: ‘kernel_type’ may be used uninitialized in this function [-Wmaybe-uninitialized]
ret = do_mount(kernel_dev, kernel_dir->name, kernel_type, flags,
^
fs/namespace.c:2697:8: note: ‘kernel_type’ was declared here
char *kernel_type;
^

Fix the warnings by simplifying copy_mount_string() as suggested by Al Viro.

Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/compat.c | 10 ++++++----
fs/internal.h | 2 +-
fs/namespace.c | 26 ++++++++------------------
3 files changed, 15 insertions(+), 23 deletions(-)

--- a/fs/compat.c
+++ b/fs/compat.c
@@ -797,8 +797,9 @@ asmlinkage long compat_sys_mount(const c
char *dir_page;
int retval;

- retval = copy_mount_string(type, &kernel_type);
- if (retval < 0)
+ kernel_type = copy_mount_string(type);
+ retval = PTR_ERR(kernel_type);
+ if (IS_ERR(kernel_type))
goto out;

dir_page = getname(dir_name);
@@ -806,8 +807,9 @@ asmlinkage long compat_sys_mount(const c
if (IS_ERR(dir_page))
goto out1;

- retval = copy_mount_string(dev_name, &kernel_dev);
- if (retval < 0)
+ kernel_dev = copy_mount_string(dev_name);
+ retval = PTR_ERR(kernel_dev);
+ if (IS_ERR(kernel_dev))
goto out2;

retval = copy_mount_options(data, &data_page);
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -60,7 +60,7 @@ extern int check_unsafe_exec(struct linu
* namespace.c
*/
extern int copy_mount_options(const void __user *, unsigned long *);
-extern int copy_mount_string(const void __user *, char **);
+extern char *copy_mount_string(const void __user *);

extern unsigned int mnt_get_count(struct vfsmount *mnt);
extern struct vfsmount *__lookup_mnt(struct vfsmount *, struct dentry *, int);
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2253,21 +2253,9 @@ int copy_mount_options(const void __user
return 0;
}

-int copy_mount_string(const void __user *data, char **where)
+char *copy_mount_string(const void __user *data)
{
- char *tmp;
-
- if (!data) {
- *where = NULL;
- return 0;
- }
-
- tmp = strndup_user(data, PAGE_SIZE);
- if (IS_ERR(tmp))
- return PTR_ERR(tmp);
-
- *where = tmp;
- return 0;
+ return data ? strndup_user(data, PAGE_SIZE) : NULL;
}

/*
@@ -2535,8 +2523,9 @@ SYSCALL_DEFINE5(mount, char __user *, de
char *kernel_dev;
unsigned long data_page;

- ret = copy_mount_string(type, &kernel_type);
- if (ret < 0)
+ kernel_type = copy_mount_string(type);
+ ret = PTR_ERR(kernel_type);
+ if (IS_ERR(kernel_type))
goto out_type;

kernel_dir = getname(dir_name);
@@ -2545,8 +2534,9 @@ SYSCALL_DEFINE5(mount, char __user *, de
goto out_dir;
}

- ret = copy_mount_string(dev_name, &kernel_dev);
- if (ret < 0)
+ kernel_dev = copy_mount_string(dev_name);
+ ret = PTR_ERR(kernel_dev);
+ if (IS_ERR(kernel_dev))
goto out_dev;

ret = copy_mount_options(data, &data_page);
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