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af_unix: Set gc_in_progress to true in unix_gc().

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Igor Ushakov reported that unix_gc() could run with gc_in_progress
being false if the work is scheduled while running:

  Thread 1         Thread 2                     Thread 3
  --------         --------                     --------
                   unix_schedule_gc()           unix_schedule_gc()
                   `- if (!gc_in_progress)      `- if (!gc_in_progress)
                      |- gc_in_progress = true     |
                      `- queue_work()              |
  unix_gc() <----------------/                     |
  |                                                |- gc_in_progress = true
  ...                                              `- queue_work()
  |                                                       |
  `- gc_in_progress = false                               |
                                                          |
  unix_gc() <---------------------------------------------'
  |
  ... /* gc_in_progress == false */
  |
  `- gc_in_progress = false

unix_peek_fpl() relies on gc_in_progress not to confuse GC
by MSG_PEEK.

Let's set gc_in_progress to true in unix_gc().

Fixes: 8b90a9f819 ("af_unix: Run GC on only one CPU.")
Reported-by: Igor Ushakov <sysroot314@gmail.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20260501073945.1884564-1-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Kuniyuki Iwashima 2026-05-01 07:39:41 +00:00 committed by Jakub Kicinski
parent bd3a4795d5
commit d82ba05263
1 changed files with 3 additions and 3 deletions
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6
net/unix/garbage.c
View File

@ -607,6 +607,8 @@ static void unix_gc(struct work_struct *work)
struct sk_buff_head hitlist;
struct sk_buff *skb;
WRITE_ONCE(gc_in_progress, true);
spin_lock(&unix_gc_lock);
if (unix_graph_state == UNIX_GRAPH_NOT_CYCLIC) {
@ -649,10 +651,8 @@ void unix_schedule_gc(struct user_struct *user)
READ_ONCE(user->unix_inflight) < UNIX_INFLIGHT_SANE_USER)
return;
if (!READ_ONCE(gc_in_progress)) {
WRITE_ONCE(gc_in_progress, true);
if (!READ_ONCE(gc_in_progress))
queue_work(system_dfl_wq, &unix_gc_work);
}
if (user && READ_ONCE(unix_graph_cyclic_sccs))
flush_work(&unix_gc_work);