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McKenney" , Boqun Feng , "H . Peter Anvin" , Paul Turner , linux-api@vger.kernel.org, Christian Brauner , Florian Weimer , David.Laight@ACULAB.COM, carlos@redhat.com, Peter Oskolkov , Alexander Mikhalitsyn , Chris Kennelly , Mathieu Desnoyers , kernel test robot , Borislav Petkov Subject: [RFC PATCH for tip] sched: Fix concurrency ID handling of usermodehelper kthreads Date: Mon, 2 Jan 2023 10:12:16 -0500 Message-Id: <20230102151216.328117-1-mathieu.desnoyers@efficios.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RDNS_NONE,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1753924517176836530?= X-GMAIL-MSGID: =?utf-8?q?1753924517176836530?= sched_mm_cid_after_execve does not expect NULL t->mm, but it may happen if a usermodehelper kthread fails when attempting to execute a binary. sched_mm_cid_fork can be issued from a usermodehelper kthread, which has t->flags PF_KTHREAD set. Fixes: af7f588d8f73 ("sched: Introduce per-memory-map concurrency ID") Reported-by: kernel test robot Link: https://lore.kernel.org/oe-lkp/202212301353.5c959d72-yujie.liu@intel.com Reported-by: Borislav Petkov Signed-off-by: Mathieu Desnoyers --- kernel/sched/core.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 048ec2417990..f99ee69867e3 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -11343,8 +11343,8 @@ void sched_mm_cid_after_execve(struct task_struct *t) struct mm_struct *mm = t->mm; unsigned long flags; - WARN_ON_ONCE((t->flags & PF_KTHREAD) || !t->mm); - + if (!mm) + return; local_irq_save(flags); t->mm_cid = mm_cid_get(mm); t->mm_cid_active = 1; @@ -11354,7 +11354,7 @@ void sched_mm_cid_after_execve(struct task_struct *t) void sched_mm_cid_fork(struct task_struct *t) { - WARN_ON_ONCE((t->flags & PF_KTHREAD) || !t->mm || t->mm_cid != -1); + WARN_ON_ONCE(!t->mm || t->mm_cid != -1); t->mm_cid_active = 1; } #endif