Commit 1f702603 authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

exec: Simplify unshare_files 



Now that exec no longer needs to return the unshared files to their
previous value there is no reason to return displaced.

Instead when unshare_fd creates a copy of the file table, call
put_files_struct before returning from unshare_files.

Acked-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
v1: https://lkml.kernel.org/r/20200817220425.9389-2-ebiederm@xmission.com
Link: https://lkml.kernel.org/r/20201120231441.29911-2-ebiederm@xmission.com


Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
parent b6043501

fs/coredump.c

+1 −4
Original line number Diff line number Diff line
@@ -585,7 +585,6 @@ void do_coredump(const kernel_siginfo_t *siginfo) 
	int ispipe;

	size_t *argv = NULL;

	int argc = 0;

	struct files_struct *displaced;

	/* require nonrelative corefile path and be extra careful */

	bool need_suid_safe = false;

	bool core_dumped = false;
@@ -791,11 +790,9 @@ void do_coredump(const kernel_siginfo_t *siginfo) 
	}



	/* get us an unshared descriptor table; almost always a no-op */

	retval = unshare_files(&displaced);

	retval = unshare_files();

	if (retval)

		goto close_fail;

	if (displaced)

		put_files_struct(displaced);

	if (!dump_interrupted()) {

		/*

		 * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would

fs/exec.c

+1 −4
Original line number Diff line number Diff line
@@ -1238,7 +1238,6 @@ void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec) 
int begin_new_exec(struct linux_binprm * bprm)

{

	struct task_struct *me = current;

	struct files_struct *displaced;

	int retval;



	/* Once we are committed compute the creds */
@@ -1259,11 +1258,9 @@ int begin_new_exec(struct linux_binprm * bprm) 
		goto out;



	/* Ensure the files table is not shared. */

	retval = unshare_files(&displaced);

	retval = unshare_files();

	if (retval)

		goto out;

	if (displaced)

		put_files_struct(displaced);



	/*

	 * Must be called _before_ exec_mmap() as bprm->mm is

include/linux/fdtable.h

+1 −1
Original line number Diff line number Diff line
@@ -109,7 +109,7 @@ struct task_struct; 
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 **);

int unshare_files(void);

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,

kernel/fork.c

+6 −6
Original line number Diff line number Diff line
@@ -3023,21 +3023,21 @@ SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 
 *	the exec layer of the kernel.

 */



int unshare_files(struct files_struct **displaced)

int unshare_files(void)

{

	struct task_struct *task = current;

	struct files_struct *copy = NULL;

	struct files_struct *old, *copy = NULL;

	int error;



	error = unshare_fd(CLONE_FILES, NR_OPEN_MAX, &copy);

	if (error || !copy) {

		*displaced = NULL;

	if (error || !copy)

		return error;

	}

	*displaced = task->files;



	old = task->files;

	task_lock(task);

	task->files = copy;

	task_unlock(task);

	put_files_struct(old);

	return 0;

}