proc: don't (ab)use ->group_leader in proc_task_readdir() paths
proc_task_readdir() does not really need "leader", first_tid() has to revalidate it anyway. Just pass proc_pid(inode) to first_tid() instead, it can do pid_task(PIDTYPE_PID) itself and read ->group_leader only if necessary. The patch also extracts the "inode is dead" code from pid_delete_dentry(dentry) into the new trivial helper, proc_inode_is_dead(inode), proc_task_readdir() uses it to return -ENOENT if this dir was removed. This is a bit racy, but the race is very inlikely and the getdents() after openndir() can see the empty "." + ".." dir only once. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Michal Hocko <mhocko@suse.cz> Cc: Sameer Nanda <snanda@chromium.org> Cc: Sergey Dyasly <dserrg@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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c986c14a6a
Коммит
d855a4b79f
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@ -1658,13 +1658,18 @@ int pid_revalidate(struct dentry *dentry, unsigned int flags)
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return 0;
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return 0;
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}
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}
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static inline bool proc_inode_is_dead(struct inode *inode)
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{
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return !proc_pid(inode)->tasks[PIDTYPE_PID].first;
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}
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int pid_delete_dentry(const struct dentry *dentry)
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int pid_delete_dentry(const struct dentry *dentry)
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{
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{
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/* Is the task we represent dead?
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/* Is the task we represent dead?
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* If so, then don't put the dentry on the lru list,
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* If so, then don't put the dentry on the lru list,
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* kill it immediately.
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* kill it immediately.
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*/
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*/
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return !proc_pid(dentry->d_inode)->tasks[PIDTYPE_PID].first;
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return proc_inode_is_dead(dentry->d_inode);
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}
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}
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const struct dentry_operations pid_dentry_operations =
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const struct dentry_operations pid_dentry_operations =
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@ -3092,34 +3097,35 @@ out_no_task:
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* In the case of a seek we start with the leader and walk nr
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* In the case of a seek we start with the leader and walk nr
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* threads past it.
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* threads past it.
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*/
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*/
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static struct task_struct *first_tid(struct task_struct *leader,
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static struct task_struct *first_tid(struct pid *pid, int tid,
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int tid, int nr, struct pid_namespace *ns)
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int nr, struct pid_namespace *ns)
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{
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{
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struct task_struct *pos;
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struct task_struct *pos, *task;
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rcu_read_lock();
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rcu_read_lock();
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/* Attempt to start with the pid of a thread */
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task = pid_task(pid, PIDTYPE_PID);
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if (!task)
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goto fail;
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/* Attempt to start with the tid of a thread */
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if (tid && (nr > 0)) {
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if (tid && (nr > 0)) {
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pos = find_task_by_pid_ns(tid, ns);
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pos = find_task_by_pid_ns(tid, ns);
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if (pos && (pos->group_leader == leader))
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if (pos && same_thread_group(pos, task))
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goto found;
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goto found;
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}
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}
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/* If nr exceeds the number of threads there is nothing todo */
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/* If nr exceeds the number of threads there is nothing todo */
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if (nr && nr >= get_nr_threads(leader))
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if (nr && nr >= get_nr_threads(task))
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goto fail;
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/* It could be unhashed before we take rcu lock */
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if (!pid_alive(leader))
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goto fail;
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goto fail;
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/* If we haven't found our starting place yet start
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/* If we haven't found our starting place yet start
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* with the leader and walk nr threads forward.
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* with the leader and walk nr threads forward.
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*/
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*/
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pos = leader;
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pos = task = task->group_leader;
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do {
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do {
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if (nr-- <= 0)
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if (nr-- <= 0)
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goto found;
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goto found;
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} while_each_thread(leader, pos);
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} while_each_thread(task, pos);
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fail:
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fail:
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pos = NULL;
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pos = NULL;
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goto out;
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goto out;
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@ -3155,25 +3161,16 @@ static struct task_struct *next_tid(struct task_struct *start)
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/* for the /proc/TGID/task/ directories */
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/* for the /proc/TGID/task/ directories */
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static int proc_task_readdir(struct file *file, struct dir_context *ctx)
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static int proc_task_readdir(struct file *file, struct dir_context *ctx)
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{
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{
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struct task_struct *leader = NULL;
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struct inode *inode = file_inode(file);
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struct task_struct *task = get_proc_task(file_inode(file));
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struct task_struct *task;
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struct pid_namespace *ns;
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struct pid_namespace *ns;
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int tid;
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int tid;
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if (!task)
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if (proc_inode_is_dead(inode))
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return -ENOENT;
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rcu_read_lock();
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if (pid_alive(task)) {
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leader = task->group_leader;
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get_task_struct(leader);
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}
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rcu_read_unlock();
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put_task_struct(task);
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if (!leader)
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return -ENOENT;
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return -ENOENT;
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if (!dir_emit_dots(file, ctx))
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if (!dir_emit_dots(file, ctx))
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goto out;
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return 0;
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/* f_version caches the tgid value that the last readdir call couldn't
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/* f_version caches the tgid value that the last readdir call couldn't
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* return. lseek aka telldir automagically resets f_version to 0.
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* return. lseek aka telldir automagically resets f_version to 0.
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@ -3181,7 +3178,7 @@ static int proc_task_readdir(struct file *file, struct dir_context *ctx)
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ns = file->f_dentry->d_sb->s_fs_info;
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ns = file->f_dentry->d_sb->s_fs_info;
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tid = (int)file->f_version;
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tid = (int)file->f_version;
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file->f_version = 0;
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file->f_version = 0;
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for (task = first_tid(leader, tid, ctx->pos - 2, ns);
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for (task = first_tid(proc_pid(inode), tid, ctx->pos - 2, ns);
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task;
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task;
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task = next_tid(task), ctx->pos++) {
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task = next_tid(task), ctx->pos++) {
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char name[PROC_NUMBUF];
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char name[PROC_NUMBUF];
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@ -3197,8 +3194,7 @@ static int proc_task_readdir(struct file *file, struct dir_context *ctx)
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break;
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break;
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}
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}
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}
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}
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out:
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put_task_struct(leader);
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return 0;
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return 0;
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}
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}
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