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 5d1c0d2dc403b4575e0309d3febac93c96843cc3..8e4ea5f1e64c698f776f252cbf1fdd714cdf45a1 100644 (file)
--- 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 cfaca3040b2f88581e96d1bea0a71500dfa06c65..c81cf642dba055544704faf4492bd0e053f5ae42 100644 (file)
--- 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)