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authorLinus Torvalds <torvalds@linux-foundation.org>2022-02-20 10:55:05 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2022-02-20 10:55:05 -0800
commitc1034d249d1453b0f4c11582515a418a5d45b570 (patch)
tree3560dbf24b6d436b07bf8ed3e1074c3001eb1f03
parent2d3409ebc87f4bc4ed23bd39e78db9ffc29eec44 (diff)
parentddc204b517e60ae64db34f9832dc41dafa77c751 (diff)
downloadlwn-c1034d249d1453b0f4c11582515a418a5d45b570.tar.gz
lwn-c1034d249d1453b0f4c11582515a418a5d45b570.zip
Merge tag 'pidfd.v5.17-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux
Pull pidfd fix from Christian Brauner: "This fixes a problem reported by lockdep when installing a pidfd via fd_install() with siglock and the tasklisk write lock held in copy_process() when calling clone()/clone3() with CLONE_PIDFD. Originally a pidfd was created prior to holding any of these locks but this required a call to ksys_close(). So quite some time ago in 6fd2fe494b17 ("copy_process(): don't use ksys_close() on cleanups") we switched to a get_unused_fd_flags() + fd_install() model. As part of that we moved fd_install() as late as possible. This was done for two main reasons. First, because we needed to ensure that we call fd_install() past the point of no return as once that's called the fd is live in the task's file table. Second, because we tried to ensure that the fd is visible in /proc/<pid>/fd/<pidfd> right when the task is visible. This fix moves the fd_install() to an even later point which means that a task will be visible in proc while the pidfd isn't yet under /proc/<pid>/fd/<pidfd>. While this is a user visible change it's very unlikely that this will have any impact. Nobody should be relying on that and if they do we need to come up with something better but again, it's doubtful this is relevant" * tag 'pidfd.v5.17-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux: copy_process(): Move fd_install() out of sighand->siglock critical section
-rw-r--r--kernel/fork.c7
1 files changed, 3 insertions, 4 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index 17d8a8c85e3b..bfa933473ff3 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2323,10 +2323,6 @@ static __latent_entropy struct task_struct *copy_process(
goto bad_fork_cancel_cgroup;
}
- /* past the last point of failure */
- if (pidfile)
- fd_install(pidfd, pidfile);
-
init_task_pid_links(p);
if (likely(p->pid)) {
ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
@@ -2375,6 +2371,9 @@ static __latent_entropy struct task_struct *copy_process(
syscall_tracepoint_update(p);
write_unlock_irq(&tasklist_lock);
+ if (pidfile)
+ fd_install(pidfd, pidfile);
+
proc_fork_connector(p);
sched_post_fork(p, args);
cgroup_post_fork(p, args);