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O_TRUNC open shouldn't fail after file truncation

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* take truncate logics into a helper (handle_truncate())
* rip it out of may_open()
* call it from the only caller of may_open() that might pass
O_TRUNC
* and do that after we'd finished with opening.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2009-12-16 03:54:00 -05:00
parent 85a17f552d
commit 7715b52122
1 changed files with 56 additions and 53 deletions
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109
fs/namei.c
View file

@ -1444,69 +1444,52 @@ int may_open(struct path *path, int acc_mode, int flag)
if (error)
return error;
error = ima_path_check(path, acc_mode ?
acc_mode & (MAY_READ | MAY_WRITE | MAY_EXEC) :
ACC_MODE(flag) & (MAY_READ | MAY_WRITE),
IMA_COUNT_UPDATE);
if (error)
return error;
/*
* An append-only file must be opened in append mode for writing.
*/
if (IS_APPEND(inode)) {
error = -EPERM;
if ((flag & FMODE_WRITE) && !(flag & O_APPEND))
goto err_out;
return -EPERM;
if (flag & O_TRUNC)
goto err_out;
return -EPERM;
}
/* O_NOATIME can only be set by the owner or superuser */
if (flag & O_NOATIME)
if (!is_owner_or_cap(inode)) {
error = -EPERM;
goto err_out;
}
if (flag & O_NOATIME && !is_owner_or_cap(inode))
return -EPERM;
/*
* Ensure there are no outstanding leases on the file.
*/
error = break_lease(inode, flag);
if (error)
goto err_out;
return error;
if (flag & O_TRUNC) {
error = get_write_access(inode);
if (error)
goto err_out;
return ima_path_check(path, acc_mode ?
acc_mode & (MAY_READ | MAY_WRITE | MAY_EXEC) :
ACC_MODE(flag) & (MAY_READ | MAY_WRITE),
IMA_COUNT_UPDATE);
}
/*
* Refuse to truncate files with mandatory locks held on them.
*/
error = locks_verify_locked(inode);
if (!error)
error = security_path_truncate(path, 0,
ATTR_MTIME|ATTR_CTIME|ATTR_OPEN);
if (!error) {
vfs_dq_init(inode);
error = do_truncate(dentry, 0,
ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
NULL);
}
put_write_access(inode);
if (error)
goto err_out;
} else
if (flag & FMODE_WRITE)
vfs_dq_init(inode);
return 0;
err_out:
ima_counts_put(path, acc_mode ?
acc_mode & (MAY_READ | MAY_WRITE | MAY_EXEC) :
ACC_MODE(flag) & (MAY_READ | MAY_WRITE));
static int handle_truncate(struct path *path)
{
struct inode *inode = path->dentry->d_inode;
int error = get_write_access(inode);
if (error)
return error;
/*
* Refuse to truncate files with mandatory locks held on them.
*/
error = locks_verify_locked(inode);
if (!error)
error = security_path_truncate(path, 0,
ATTR_MTIME|ATTR_CTIME|ATTR_OPEN);
if (!error) {
error = do_truncate(path->dentry, 0,
ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
NULL);
}
put_write_access(inode);
return error;
}
@ -1561,7 +1544,7 @@ static inline int open_to_namei_flags(int flag)
return flag;
}
static int open_will_write_to_fs(int flag, struct inode *inode)
static int open_will_truncate(int flag, struct inode *inode)
{
/*
* We'll never write to the fs underlying
@ -1586,7 +1569,7 @@ struct file *do_filp_open(int dfd, const char *pathname,
struct path path, save;
struct dentry *dir;
int count = 0;
int will_write;
int will_truncate;
int flag = open_to_namei_flags(open_flag);
/*
@ -1752,28 +1735,48 @@ ok:
* be avoided. Taking this mnt write here
* ensures that (2) can not occur.
*/
will_write = open_will_write_to_fs(flag, nd.path.dentry->d_inode);
if (will_write) {
will_truncate = open_will_truncate(flag, nd.path.dentry->d_inode);
if (will_truncate) {
error = mnt_want_write(nd.path.mnt);
if (error)
goto exit;
}
error = may_open(&nd.path, acc_mode, flag);
if (error) {
if (will_write)
if (will_truncate)
mnt_drop_write(nd.path.mnt);
goto exit;
}
filp = nameidata_to_filp(&nd, open_flag);
if (IS_ERR(filp))
if (IS_ERR(filp)) {
ima_counts_put(&nd.path,
acc_mode & (MAY_READ | MAY_WRITE | MAY_EXEC));
if (will_truncate)
mnt_drop_write(nd.path.mnt);
if (nd.root.mnt)
path_put(&nd.root);
return filp;
}
if (acc_mode & MAY_WRITE)
vfs_dq_init(nd.path.dentry->d_inode);
if (will_truncate) {
error = handle_truncate(&nd.path);
if (error) {
mnt_drop_write(nd.path.mnt);
fput(filp);
if (nd.root.mnt)
path_put(&nd.root);
return ERR_PTR(error);
}
}
/*
* It is now safe to drop the mnt write
* because the filp has had a write taken
* on its behalf.
*/
if (will_write)
if (will_truncate)
mnt_drop_write(nd.path.mnt);
if (nd.root.mnt)
path_put(&nd.root);