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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: Christian 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: Eric W. Biederman <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2020-11-20 17:14:19 -06:00
parent b604350128
commit 1f702603e7
4 changed files with 9 additions and 15 deletions
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5
fs/coredump.c
View File

@ -585,7 +585,6 @@ void do_coredump(const kernel_siginfo_t *siginfo)
int ispipe; int ispipe;
size_t *argv = NULL; size_t *argv = NULL;
int argc = 0; int argc = 0;
struct files_struct *displaced;
/* require nonrelative corefile path and be extra careful */ /* require nonrelative corefile path and be extra careful */
bool need_suid_safe = false; bool need_suid_safe = false;
bool core_dumped = 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 */ /* get us an unshared descriptor table; almost always a no-op */
retval = unshare_files(&displaced); retval = unshare_files();
if (retval) if (retval)
goto close_fail; goto close_fail;
if (displaced)
put_files_struct(displaced);
if (!dump_interrupted()) { if (!dump_interrupted()) {
/* /*
* umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would

5
fs/exec.c
View File

@ -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) int begin_new_exec(struct linux_binprm * bprm)
{ {
struct task_struct *me = current; struct task_struct *me = current;
struct files_struct *displaced;
int retval; int retval;
/* Once we are committed compute the creds */ /* Once we are committed compute the creds */
@ -1259,11 +1258,9 @@ int begin_new_exec(struct linux_binprm * bprm)
goto out; goto out;
/* Ensure the files table is not shared. */ /* Ensure the files table is not shared. */
retval = unshare_files(&displaced); retval = unshare_files();
if (retval) if (retval)
goto out; goto out;
if (displaced)
put_files_struct(displaced);
/* /*
* Must be called _before_ exec_mmap() as bprm->mm is * Must be called _before_ exec_mmap() as bprm->mm is

2
include/linux/fdtable.h
View File

@ -109,7 +109,7 @@ struct task_struct;
struct files_struct *get_files_struct(struct task_struct *); struct files_struct *get_files_struct(struct task_struct *);
void put_files_struct(struct files_struct *fs); void put_files_struct(struct files_struct *fs);
void reset_files_struct(struct files_struct *); 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; struct files_struct *dup_fd(struct files_struct *, unsigned, int *) __latent_entropy;
void do_close_on_exec(struct files_struct *); void do_close_on_exec(struct files_struct *);
int iterate_fd(struct files_struct *, unsigned, int iterate_fd(struct files_struct *, unsigned,

12
kernel/fork.c
View File

@ -3023,21 +3023,21 @@ SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
* the exec layer of the kernel. * the exec layer of the kernel.
*/ */
int unshare_files(struct files_struct **displaced) int unshare_files(void)
{ {
struct task_struct *task = current; struct task_struct *task = current;
struct files_struct *copy = NULL; struct files_struct *old, *copy = NULL;
int error; int error;
error = unshare_fd(CLONE_FILES, NR_OPEN_MAX, &copy); error = unshare_fd(CLONE_FILES, NR_OPEN_MAX, &copy);
if (error || !copy) { if (error || !copy)
*displaced = NULL;
return error; return error;
}
*displaced = task->files; old = task->files;
task_lock(task); task_lock(task);
task->files = copy; task->files = copy;
task_unlock(task); task_unlock(task);
put_files_struct(old);
return 0; return 0;
} }