diff options
| author | Christian Brauner <christian.brauner@ubuntu.com> | 2020-06-03 21:48:55 +0200 |
|---|---|---|
| committer | Christian Brauner <christian.brauner@ubuntu.com> | 2020-06-17 00:07:38 +0200 |
| commit | 60997c3d45d9a67daf01c56d805ae4fec37e0bd8 (patch) | |
| tree | 8f915556e039b20018e6d95ab154048a0fddf576 /include/linux/fdtable.h | |
| parent | 2c5db60e46ad7f03789fe7e2beedb15496930468 (diff) | |
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>
Diffstat (limited to 'include/linux/fdtable.h')
| -rw-r--r-- | include/linux/fdtable.h | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h index fcd07181a365..a32bf47c593e 100644 --- a/include/linux/fdtable.h +++ b/include/linux/fdtable.h @@ -22,6 +22,7 @@ * as this is the granularity returned by copy_fdset(). */ #define NR_OPEN_DEFAULT BITS_PER_LONG +#define NR_OPEN_MAX ~0U struct fdtable { unsigned int max_fds; @@ -109,7 +110,7 @@ struct files_struct *get_files_struct(struct task_struct *); void put_files_struct(struct files_struct *fs); void reset_files_struct(struct files_struct *); int unshare_files(struct files_struct **); -struct files_struct *dup_fd(struct files_struct *, int *) __latent_entropy; +struct files_struct *dup_fd(struct files_struct *, unsigned, int *) __latent_entropy; void do_close_on_exec(struct files_struct *); int iterate_fd(struct files_struct *, unsigned, int (*)(const void *, struct file *, unsigned), @@ -121,9 +122,10 @@ extern void __fd_install(struct files_struct *files, unsigned int fd, struct file *file); extern int __close_fd(struct files_struct *files, unsigned int fd); -extern int __close_range(struct files_struct *files, unsigned int fd, - unsigned int max_fd); +extern int __close_range(unsigned int fd, unsigned int max_fd, unsigned int flags); extern int __close_fd_get_file(unsigned int fd, struct file **res); +extern int unshare_fd(unsigned long unshare_flags, unsigned int max_fds, + struct files_struct **new_fdp); extern struct kmem_cache *files_cachep; |