Subject: + proc-dont-abuse-group_leader-in-proc_task_readdir-paths.patch added to -mm tree
To: oleg@xxxxxxxxxx,dserrg@xxxxxxxxx,ebiederm@xxxxxxxxxxxx,mhocko@xxxxxxx,snanda@xxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Wed, 20 Nov 2013 14:53:09 -0800
The patch titled
Subject: proc: don't (ab)use ->group_leader in proc_task_readdir() paths
has been added to the -mm tree. Its filename is
proc-dont-abuse-group_leader-in-proc_task_readdir-paths.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/proc-dont-abuse-group_leader-in-proc_task_readdir-paths.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/proc-dont-abuse-group_leader-in-proc_task_readdir-paths.patch
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------------------------------------------------------
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: 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@xxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: Sameer Nanda <snanda@xxxxxxxxxxxx>
Cc: Sergey Dyasly <dserrg@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/base.c | 52 +++++++++++++++++++++--------------------------
1 file changed, 24 insertions(+), 28 deletions(-)
diff -puN fs/proc/base.c~proc-dont-abuse-group_leader-in-proc_task_readdir-paths fs/proc/base.c
--- a/fs/proc/base.c~proc-dont-abuse-group_leader-in-proc_task_readdir-paths
+++ a/fs/proc/base.c
@@ -1652,13 +1652,18 @@ int pid_revalidate(struct dentry *dentry
return 0;
}
+static inline bool proc_inode_is_dead(struct inode *inode)
+{
+ return !proc_pid(inode)->tasks[PIDTYPE_PID].first;
+}
+
int pid_delete_dentry(const struct dentry *dentry)
{
/* Is the task we represent dead?
* If so, then don't put the dentry on the lru list,
* kill it immediately.
*/
- return !proc_pid(dentry->d_inode)->tasks[PIDTYPE_PID].first;
+ return proc_inode_is_dead(dentry->d_inode);
}
const struct dentry_operations pid_dentry_operations =
@@ -3086,34 +3091,35 @@ out_no_task:
* In the case of a seek we start with the leader and walk nr
* threads past it.
*/
-static struct task_struct *first_tid(struct task_struct *leader,
- int tid, int nr, struct pid_namespace *ns)
+static struct task_struct *first_tid(struct pid *pid, int tid,
+ int nr, struct pid_namespace *ns)
{
- struct task_struct *pos;
+ struct task_struct *pos, *task;
rcu_read_lock();
- /* Attempt to start with the pid of a thread */
+ task = pid_task(pid, PIDTYPE_PID);
+ if (!task)
+ goto fail;
+
+ /* Attempt to start with the tid of a thread */
if (tid && (nr > 0)) {
pos = find_task_by_pid_ns(tid, ns);
- if (pos && (pos->group_leader == leader))
+ if (pos && same_thread_group(pos, task))
goto found;
}
/* If nr exceeds the number of threads there is nothing todo */
- if (nr && nr >= get_nr_threads(leader))
- goto fail;
- /* It could be unhashed before we take rcu lock */
- if (!pid_alive(leader))
+ if (nr && nr >= get_nr_threads(task))
goto fail;
/* If we haven't found our starting place yet start
* with the leader and walk nr threads forward.
*/
- pos = leader;
+ pos = task = task->group_leader;
do {
if (nr-- <= 0)
goto found;
- } while_each_thread(leader, pos);
+ } while_each_thread(task, pos);
fail:
pos = NULL;
goto out;
@@ -3149,25 +3155,16 @@ static struct task_struct *next_tid(stru
/* for the /proc/TGID/task/ directories */
static int proc_task_readdir(struct file *file, struct dir_context *ctx)
{
- struct task_struct *leader = NULL;
- struct task_struct *task = get_proc_task(file_inode(file));
+ struct inode *inode = file_inode(file);
+ struct task_struct *task;
struct pid_namespace *ns;
int tid;
- if (!task)
- return -ENOENT;
- rcu_read_lock();
- if (pid_alive(task)) {
- leader = task->group_leader;
- get_task_struct(leader);
- }
- rcu_read_unlock();
- put_task_struct(task);
- if (!leader)
+ if (proc_inode_is_dead(inode))
return -ENOENT;
if (!dir_emit_dots(file, ctx))
- goto out;
+ return 0;
/* f_version caches the tgid value that the last readdir call couldn't
* return. lseek aka telldir automagically resets f_version to 0.
@@ -3175,7 +3172,7 @@ static int proc_task_readdir(struct file
ns = file->f_dentry->d_sb->s_fs_info;
tid = (int)file->f_version;
file->f_version = 0;
- for (task = first_tid(leader, tid, ctx->pos - 2, ns);
+ for (task = first_tid(proc_pid(inode), tid, ctx->pos - 2, ns);
task;
task = next_tid(task), ctx->pos++) {
char name[PROC_NUMBUF];
@@ -3191,8 +3188,7 @@ static int proc_task_readdir(struct file
break;
}
}
-out:
- put_task_struct(leader);
+
return 0;
}
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
origin.patch
autofs4-allow-autofs-to-work-outside-the-initial-pid-namespace.patch
autofs4-translate-pids-to-the-right-namespace-for-the-daemon.patch
coredump-set_dumpable-fix-the-theoretical-race-with-itself.patch
coredump-kill-mmf_dumpable-and-mmf_dump_securely.patch
coredump-make-__get_dumpable-get_dumpable-inline-kill-fs-coredumph.patch
exit_state-kill-task_is_dead.patch
proc-cleanup-simplify-get_task_state-task_state_array.patch
proc-fix-the-potential-use-after-free-in-first_tid.patch
proc-change-first_tid-to-use-while_each_thread-rather-than-next_thread.patch
proc-dont-abuse-group_leader-in-proc_task_readdir-paths.patch
proc-fix-f_pos-overflows-in-first_tid.patch
fork-no-need-to-initialize-child-exit_state.patch
linux-next.patch
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