On Wed, Jan 03, 2024 at 07:11:56PM +0100, Ahmad Fatoum wrote:
> For use with the newly added openat and friends API, add O_PATH file
> descriptors that are not usable for doing actual I/O, but only for use
> as dirfd.
>
> Signed-off-by: Ahmad Fatoum <a.fat...@pengutronix.de>
> ---
> fs/fs.c | 58 +++++++++++++++++++++++++++++--------------------
> include/fcntl.h | 1 +
> 2 files changed, 35 insertions(+), 24 deletions(-)
>
> diff --git a/fs/fs.c b/fs/fs.c
> index 6b71440318af..54f38aa2e63b 100644
> --- a/fs/fs.c
> +++ b/fs/fs.c
> @@ -325,12 +325,16 @@ static void put_file(FILE *f)
> dput(f->dentry);
> }
>
> -static FILE *fd_to_file(int fd)
> +static FILE *fd_to_file(int fd, bool allow_pathonly)
This parameter name confuses me. I read this as "only O_PATH is
allowed". Maybe rename this to "o_path_allowed" or "o_path_ok"?
Sascha
> {
> if (fd < 0 || fd >= MAX_FILES || !files[fd].in_use) {
> errno = EBADF;
> return ERR_PTR(-errno);
> }
> + if (!allow_pathonly && (files[fd].flags & O_PATH)) {
> + errno = EINVAL;
> + return ERR_PTR(-errno);
> + }
>
> return &files[fd];
> }
> @@ -359,7 +363,7 @@ static int fsdev_truncate(struct device *dev, FILE *f,
> loff_t length)
>
> int ftruncate(int fd, loff_t length)
> {
> - FILE *f = fd_to_file(fd);
> + FILE *f = fd_to_file(fd, false);
> int ret;
>
> if (IS_ERR(f))
> @@ -381,7 +385,7 @@ int ftruncate(int fd, loff_t length)
> int ioctl(int fd, int request, void *buf)
> {
> struct fs_driver *fsdrv;
> - FILE *f = fd_to_file(fd);
> + FILE *f = fd_to_file(fd, false);
> int ret;
>
> if (IS_ERR(f))
> @@ -426,7 +430,7 @@ static ssize_t __read(FILE *f, void *buf, size_t count)
> ssize_t pread(int fd, void *buf, size_t count, loff_t offset)
> {
> loff_t pos;
> - FILE *f = fd_to_file(fd);
> + FILE *f = fd_to_file(fd, false);
> int ret;
>
> if (IS_ERR(f))
> @@ -443,7 +447,7 @@ EXPORT_SYMBOL(pread);
>
> ssize_t read(int fd, void *buf, size_t count)
> {
> - FILE *f = fd_to_file(fd);
> + FILE *f = fd_to_file(fd, false);
> int ret;
>
> if (IS_ERR(f))
> @@ -495,7 +499,7 @@ static ssize_t __write(FILE *f, const void *buf, size_t
> count)
> ssize_t pwrite(int fd, const void *buf, size_t count, loff_t offset)
> {
> loff_t pos;
> - FILE *f = fd_to_file(fd);
> + FILE *f = fd_to_file(fd, false);
> int ret;
>
> if (IS_ERR(f))
> @@ -512,7 +516,7 @@ EXPORT_SYMBOL(pwrite);
>
> ssize_t write(int fd, const void *buf, size_t count)
> {
> - FILE *f = fd_to_file(fd);
> + FILE *f = fd_to_file(fd, false);
> int ret;
>
> if (IS_ERR(f))
> @@ -529,7 +533,7 @@ EXPORT_SYMBOL(write);
> int flush(int fd)
> {
> struct fs_driver *fsdrv;
> - FILE *f = fd_to_file(fd);
> + FILE *f = fd_to_file(fd, false);
> int ret;
>
> if (IS_ERR(f))
> @@ -547,7 +551,7 @@ int flush(int fd)
> loff_t lseek(int fd, loff_t offset, int whence)
> {
> struct fs_driver *fsdrv;
> - FILE *f = fd_to_file(fd);
> + FILE *f = fd_to_file(fd, false);
> loff_t pos;
> int ret;
>
> @@ -600,7 +604,7 @@ EXPORT_SYMBOL(lseek);
> int erase(int fd, loff_t count, loff_t offset)
> {
> struct fs_driver *fsdrv;
> - FILE *f = fd_to_file(fd);
> + FILE *f = fd_to_file(fd, false);
> int ret;
>
> if (IS_ERR(f))
> @@ -629,7 +633,7 @@ EXPORT_SYMBOL(erase);
> int protect(int fd, size_t count, loff_t offset, int prot)
> {
> struct fs_driver *fsdrv;
> - FILE *f = fd_to_file(fd);
> + FILE *f = fd_to_file(fd, false);
> int ret;
>
> if (IS_ERR(f))
> @@ -656,7 +660,7 @@ EXPORT_SYMBOL(protect);
> int discard_range(int fd, loff_t count, loff_t offset)
> {
> struct fs_driver *fsdrv;
> - FILE *f = fd_to_file(fd);
> + FILE *f = fd_to_file(fd, false);
> int ret;
>
> if (IS_ERR(f))
> @@ -697,7 +701,7 @@ int protect_file(const char *file, int prot)
> void *memmap(int fd, int flags)
> {
> struct fs_driver *fsdrv;
> - FILE *f = fd_to_file(fd);
> + FILE *f = fd_to_file(fd, false);
> void *retp = MAP_FAILED;
> int ret;
>
> @@ -721,20 +725,23 @@ EXPORT_SYMBOL(memmap);
>
> int close(int fd)
> {
> - struct fs_driver *fsdrv;
> - FILE *f = fd_to_file(fd);
> + FILE *f = fd_to_file(fd, true);
> int ret = 0;
>
> if (IS_ERR(f))
> return -errno;
>
> - fsdrv = f->fsdev->driver;
> + if (!(f->flags & O_PATH)) {
> + struct fs_driver *fsdrv;
>
> - if (fsdrv != ramfs_driver)
> - assert_command_context();
> + fsdrv = f->fsdev->driver;
>
> - if (fsdrv->close)
> - ret = fsdrv->close(&f->fsdev->dev, f);
> + if (fsdrv != ramfs_driver)
> + assert_command_context();
> +
> + if (fsdrv->close)
> + ret = fsdrv->close(&f->fsdev->dev, f);
> + }
>
> put_file(f);
>
> @@ -1056,7 +1063,7 @@ static void stat_inode(struct inode *inode, struct stat
> *s)
>
> int fstat(int fd, struct stat *s)
> {
> - FILE *f = fd_to_file(fd);
> + FILE *f = fd_to_file(fd, true);
>
> if (IS_ERR(f))
> return -errno;
> @@ -2173,7 +2180,7 @@ static const char *path_init(int dirfd, struct
> nameidata *nd, unsigned flags)
> * whether paths are absolute with openat(-1, path, O_PATH)
> */
> if (dirfd != AT_FDCWD)
> - f = fd_to_file(dirfd);
> + f = fd_to_file(dirfd, true);
>
> if (*s == '/') {
> get_root(&nd->path);
> @@ -2590,7 +2597,7 @@ int openat(int dirfd, const char *pathname, int flags)
> error = -ENOENT;
> goto out1;
> }
> - } else {
> + } else if (!(flags & O_PATH)) {
> if (d_is_dir(dentry) && !dentry_is_tftp(dentry)) {
> error = -EISDIR;
> goto out1;
> @@ -2617,6 +2624,9 @@ int openat(int dirfd, const char *pathname, int flags)
>
> f->fsdev = fsdev;
>
> + if (flags & O_PATH)
> + return f->no;
> +
> if (fsdrv->open) {
> char *pathname = dpath(dentry, fsdev->vfsmount.mnt_root);
>
> @@ -2653,7 +2663,7 @@ static const char *fd_getpath(int fd)
> if (fd < 0)
> return ERR_PTR(errno_set(fd));
>
> - f = fd_to_file(fd);
> + f = fd_to_file(fd, true);
> if (IS_ERR(f))
> return ERR_CAST(f);
>
> diff --git a/include/fcntl.h b/include/fcntl.h
> index a6ed50b92eaf..a3f5d96cd0ac 100644
> --- a/include/fcntl.h
> +++ b/include/fcntl.h
> @@ -23,6 +23,7 @@
> #define O_APPEND 00002000
> #define O_DIRECTORY 00200000 /* must be a directory */
> #define O_NOFOLLOW 00400000 /* don't follow links */
> +#define O_PATH 02000000 /* open as path */
> #define __O_TMPFILE 020000000
>
> #define O_TMPFILE (__O_TMPFILE | O_DIRECTORY)
> --
> 2.39.2
>
>
>
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