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[PATCH] fix de_thread() vs send_group_sigqueue() race
When non-leader thread does exec, de_thread calls release_task(leader) before calling exit_itimers(). If local timer interrupt happens in between, it can oops in send_group_sigqueue() while taking ->sighand->siglock == NULL. However, we can't change send_group_sigqueue() to check p->signal != NULL, because sys_timer_create() does get_task_struct() only in SIGEV_THREAD_ID case. So it is possible that this task_struct was already freed and we can't trust p->signal. This patch changes de_thread() so that leader released after exit_itimers() call. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Chris Wright <chrisw@osdl.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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parent
d212503f82
commit
6b85cfab9d
1 changed files with 7 additions and 3 deletions
10
fs/exec.c
10
fs/exec.c
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@ -593,6 +593,7 @@ static inline int de_thread(struct task_struct *tsk)
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struct signal_struct *sig = tsk->signal;
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struct sighand_struct *newsighand, *oldsighand = tsk->sighand;
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spinlock_t *lock = &oldsighand->siglock;
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struct task_struct *leader = NULL;
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int count;
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/*
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@ -668,7 +669,7 @@ static inline int de_thread(struct task_struct *tsk)
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* and to assume its PID:
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*/
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if (!thread_group_leader(current)) {
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struct task_struct *leader = current->group_leader, *parent;
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struct task_struct *parent;
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struct dentry *proc_dentry1, *proc_dentry2;
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unsigned long exit_state, ptrace;
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@ -677,6 +678,7 @@ static inline int de_thread(struct task_struct *tsk)
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* It should already be zombie at this point, most
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* of the time.
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*/
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leader = current->group_leader;
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while (leader->exit_state != EXIT_ZOMBIE)
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yield();
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@ -736,7 +738,6 @@ static inline int de_thread(struct task_struct *tsk)
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proc_pid_flush(proc_dentry2);
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BUG_ON(exit_state != EXIT_ZOMBIE);
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release_task(leader);
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}
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/*
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@ -746,8 +747,11 @@ static inline int de_thread(struct task_struct *tsk)
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sig->flags = 0;
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no_thread_group:
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BUG_ON(atomic_read(&sig->count) != 1);
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exit_itimers(sig);
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if (leader)
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release_task(leader);
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BUG_ON(atomic_read(&sig->count) != 1);
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if (atomic_read(&oldsighand->count) == 1) {
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/*
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