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BACKPORT: umh: add exit routine for UMH process

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A UMH process which is created by the fork_usermode_blob() such as
bpfilter needs to release members of the umh_info when process is
terminated.
But the do_exit() does not release members of the umh_info. hence module
which uses UMH needs own code to detect whether UMH process is
terminated or not.
But this implementation needs extra code for checking the status of
UMH process. it eventually makes the code more complex.

The new PF_UMH flag is added and it is used to identify UMH processes.
The exit_umh() does not release members of the umh_info.
Hence umh_info->cleanup callback should release both members of the
umh_info and the private data.

Suggested-by: David S. Miller <davem@davemloft.net>
Change-Id: I860a2582ecffb61d3cec6ff86b53eb6fe85e27e3
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Taehee Yoo
2019-01-09 02:23:56 +09:00
committed by Samuel Pascua
parent ee7cc78e74
commit 7e4c5b6faa
4 changed files with 43 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
include/linux/sched.h
View File

@@ -1585,6 +1585,7 @@ extern struct pid *cad_pid;
#define PF_RANDOMIZE 0x00400000 /* Randomize virtual address space */
#define PF_SWAPWRITE 0x00800000 /* Allowed to write to swap */
#define PF_MEMSTALL 0x01000000 /* Stalled due to lack of memory */
#define PF_UMH 0x02000000 /* I'm an Usermodehelper process */
#define PF_NO_SETAFFINITY 0x04000000 /* Userland is not allowed to meddle with cpus_allowed */
#define PF_MCE_EARLY 0x08000000 /* Early kill for mce process policy */
#define PF_WAKE_UP_IDLE 0x10000000 /* TTWU on an idle CPU */
@@ -2003,4 +2004,12 @@ static inline void set_wake_up_idle(bool enabled)
current->flags &= ~PF_WAKE_UP_IDLE;
}
void __exit_umh(struct task_struct *tsk);
static inline void exit_umh(struct task_struct *tsk)
{
if (unlikely(tsk->flags & PF_UMH))
__exit_umh(tsk);
}
#endif

2
include/linux/umh.h
View File

@@ -47,6 +47,8 @@ struct umh_info {
const char *cmdline;
struct file *pipe_to_umh;
struct file *pipe_from_umh;
struct list_head list;
void (*cleanup)(struct umh_info *info);
pid_t pid;
};
int fork_usermode_blob(void *data, size_t len, struct umh_info *info);

1
kernel/exit.c
View File

@@ -939,6 +939,7 @@ void __noreturn do_exit(long code)
exit_task_namespaces(tsk);
exit_task_work(tsk);
exit_thread(tsk);
exit_umh(tsk);
/*
* Flush inherited counters to the parent - before the parent

33
kernel/umh.c
View File

@@ -38,6 +38,8 @@ static kernel_cap_t usermodehelper_bset = CAP_FULL_SET;
static kernel_cap_t usermodehelper_inheritable = CAP_FULL_SET;
static DEFINE_SPINLOCK(umh_sysctl_lock);
static DECLARE_RWSEM(umhelper_sem);
static LIST_HEAD(umh_list);
static DEFINE_MUTEX(umh_list_lock);
static void call_usermodehelper_freeinfo(struct subprocess_info *info)
{
@@ -109,10 +111,12 @@ static int call_usermodehelper_exec_async(void *data)
commit_creds(new);
sub_info->pid = task_pid_nr(current);
if (sub_info->file)
if (sub_info->file) {
retval = do_execve_file(sub_info->file,
sub_info->argv, sub_info->envp);
else
if (!retval)
current->flags |= PF_UMH;
} else
retval = do_execve(getname_kernel(sub_info->path),
(const char __user *const __user *)sub_info->argv,
(const char __user *const __user *)sub_info->envp);
@@ -526,6 +530,11 @@ int fork_usermode_blob(void *data, size_t len, struct umh_info *info)
goto out;
err = call_usermodehelper_exec(sub_info, UMH_WAIT_EXEC);
if (!err) {
mutex_lock(&umh_list_lock);
list_add(&info->list, &umh_list);
mutex_unlock(&umh_list_lock);
}
out:
fput(file);
return err;
@@ -693,6 +702,26 @@ static int proc_cap_handler(struct ctl_table *table, int write,
return 0;
}
void __exit_umh(struct task_struct *tsk)
{
struct umh_info *info;
pid_t pid = tsk->pid;
mutex_lock(&umh_list_lock);
list_for_each_entry(info, &umh_list, list) {
if (info->pid == pid) {
list_del(&info->list);
mutex_unlock(&umh_list_lock);
goto out;
}
}
mutex_unlock(&umh_list_lock);
return;
out:
if (info->cleanup)
info->cleanup(info);
}
struct ctl_table usermodehelper_table[] = {
{
.procname = "bset",