From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Thu, 27 Mar 2025 13:29:45 +0000 (-0400)
Subject: rseq: Eliminate useless task_work on execve
X-Git-Tag: v6.15-rc1~5^2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=169eae7711ea4b745e2d33d53e7b88689b10e1a0;p=thirdparty%2Flinux.git

rseq: Eliminate useless task_work on execve

Eliminate a useless task_work on execve by moving the call to
rseq_set_notify_resume() from sched_mm_cid_after_execve() to the error
path of bprm_execve().

The call to rseq_set_notify_resume() from sched_mm_cid_after_execve() is
pointless in the success case, because rseq_execve() will clear the rseq
pointer before returning to userspace.

sched_mm_cid_after_execve() is called from both the success and error
paths of bprm_execve(). The call to rseq_set_notify_resume() is needed
on error because the mm_cid may have changed.

Also move the rseq_execve() to right after sched_mm_cid_after_execve()
in bprm_execve().

[ mingo: Merged to a recent upstream kernel, extended the changelog. ]

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250327132945.1558783-1-mathieu.desnoyers@efficios.com
---

diff --git a/fs/exec.c b/fs/exec.c
index 5d1c0d2dc403b..8e4ea5f1e64c6 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1864,9 +1864,9 @@ static int bprm_execve(struct linux_binprm *bprm)
 		goto out;
 
 	sched_mm_cid_after_execve(current);
+	rseq_execve(current);
 	/* execve succeeded */
 	current->in_execve = 0;
-	rseq_execve(current);
 	user_events_execve(current);
 	acct_update_integrals(current);
 	task_numa_free(current, false);
@@ -1883,6 +1883,7 @@ out:
 		force_fatal_sig(SIGSEGV);
 
 	sched_mm_cid_after_execve(current);
+	rseq_set_notify_resume(current);
 	current->in_execve = 0;
 
 	return retval;
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index cfaca3040b2f8..c81cf642dba05 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -10703,7 +10703,6 @@ void sched_mm_cid_after_execve(struct task_struct *t)
 		smp_mb();
 		t->last_mm_cid = t->mm_cid = mm_cid_get(rq, t, mm);
 	}
-	rseq_set_notify_resume(t);
 }
 
 void sched_mm_cid_fork(struct task_struct *t)