linux-kernelorg-stable/include/uapi/linux/close_range.h

/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
#ifndef _UAPI_LINUX_CLOSE_RANGE_H
#define _UAPI_LINUX_CLOSE_RANGE_H

/* Unshare the file descriptor table before closing file descriptors. */
#define CLOSE_RANGE_UNSHARE	(1U << 1)

#endif /* _UAPI_LINUX_CLOSE_RANGE_H */
close_range: add CLOSE_RANGE_UNSHARE One of the use-cases of close_range() is to drop file descriptors just before execve(). This would usually be expressed in the sequence: unshare(CLONE_FILES); close_range(3, ~0U); as pointed out by Linus it might be desirable to have this be a part of close_range() itself under a new flag CLOSE_RANGE_UNSHARE. This expands {dup,unshare)_fd() to take a max_fds argument that indicates the maximum number of file descriptors to copy from the old struct files. When the user requests that all file descriptors are supposed to be closed via close_range(min, max) then we can cap via unshare_fd(min) and hence don't need to do any of the heavy fput() work for everything above min. The patch makes it so that if CLOSE_RANGE_UNSHARE is requested and we do in fact currently share our file descriptor table we create a new private copy. We then close all fds in the requested range and finally after we're done we install the new fd table. Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> 2020-06-03 19:48:55 +00:00			`/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */`
			`#ifndef _UAPI_LINUX_CLOSE_RANGE_H`
			`#define _UAPI_LINUX_CLOSE_RANGE_H`

			`/* Unshare the file descriptor table before closing file descriptors. */`
			`#define CLOSE_RANGE_UNSHARE (1U << 1)`

			`#endif /* _UAPI_LINUX_CLOSE_RANGE_H */`