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authorOleg Nesterov <oleg@redhat.com>2013-06-14 21:09:47 +0200
committerAl Viro <viro@zeniv.linux.org.uk>2013-06-15 05:39:08 +0400
commite7b2c4069252732d52f1de6d1f7c82d99a156659 (patch)
tree61058c0dd3806eaf067d1e6cf1634aa1acc9336e
parent698b8223631472bf982ed570b0812faa61955683 (diff)
downloadlinux-e7b2c4069252732d52f1de6d1f7c82d99a156659.tar.bz2
fput: task_work_add() can fail if the caller has passed exit_task_work()
fput() assumes that it can't be called after exit_task_work() but this is not true, for example free_ipc_ns()->shm_destroy() can do this. In this case fput() silently leaks the file. Change it to fallback to delayed_fput_work if task_work_add() fails. The patch looks complicated but it is not, it changes the code from if (PF_KTHREAD) { schedule_work(...); return; } task_work_add(...) to if (!PF_KTHREAD) { if (!task_work_add(...)) return; /* fallback */ } schedule_work(...); As for shm_destroy() in particular, we could make another fix but I think this change makes sense anyway. There could be another similar user, it is not safe to assume that task_work_add() can't fail. Reported-by: Andrey Vagin <avagin@openvz.org> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r--fs/file_table.c19
1 files changed, 10 insertions, 9 deletions
diff --git a/fs/file_table.c b/fs/file_table.c
index cd4d87a82951..485dc0eddd67 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -306,17 +306,18 @@ void fput(struct file *file)
{
if (atomic_long_dec_and_test(&file->f_count)) {
struct task_struct *task = current;
+ unsigned long flags;
+
file_sb_list_del(file);
- if (unlikely(in_interrupt() || task->flags & PF_KTHREAD)) {
- unsigned long flags;
- spin_lock_irqsave(&delayed_fput_lock, flags);
- list_add(&file->f_u.fu_list, &delayed_fput_list);
- schedule_work(&delayed_fput_work);
- spin_unlock_irqrestore(&delayed_fput_lock, flags);
- return;
+ if (likely(!in_interrupt() && !(task->flags & PF_KTHREAD))) {
+ init_task_work(&file->f_u.fu_rcuhead, ____fput);
+ if (!task_work_add(task, &file->f_u.fu_rcuhead, true))
+ return;
}
- init_task_work(&file->f_u.fu_rcuhead, ____fput);
- task_work_add(task, &file->f_u.fu_rcuhead, true);
+ spin_lock_irqsave(&delayed_fput_lock, flags);
+ list_add(&file->f_u.fu_list, &delayed_fput_list);
+ schedule_work(&delayed_fput_work);
+ spin_unlock_irqrestore(&delayed_fput_lock, flags);
}
}