linux-kernel - [tip:x86/urgent] x86/process: Delete useless check for dead process with LDT

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Date:   Tue, 16 Jul 2019 14:23:30 -0700
From:   tip-bot for Jann Horn <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     jannh@...gle.com, tglx@...utronix.de, hpa@...or.com,
        linux-kernel@...r.kernel.org, mingo@...nel.org
Subject: [tip:x86/urgent] x86/process: Delete useless check for dead process
 with LDT

Commit-ID:  68c2976d7d93392d33ccd8871e9e61b33b5e640f
Gitweb:     https://git.kernel.org/tip/68c2976d7d93392d33ccd8871e9e61b33b5e640f
Author:     Jann Horn <jannh@...gle.com>
AuthorDate: Sat, 13 Jul 2019 00:41:52 +0200
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Tue, 16 Jul 2019 23:13:50 +0200

x86/process: Delete useless check for dead process with LDT

At release_thread(), ->mm is NULL; and it is fine for the former mm to
still have an LDT. Delete this check in process_64.c, similar to
commit 2684927c6b93 ("[PATCH] x86: Deprecate useless bug"), which did the
same in process_32.c.

Signed-off-by: Jann Horn <jannh@...gle.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Link: https://lkml.kernel.org/r/20190712224152.13129-1-jannh@google.com

---
 arch/x86/kernel/process_64.c | 12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 250e4c4ac6d9..af64519b2695 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -143,17 +143,7 @@ void __show_regs(struct pt_regs *regs, enum show_regs_mode mode)
 
 void release_thread(struct task_struct *dead_task)
 {
-	if (dead_task->mm) {
-#ifdef CONFIG_MODIFY_LDT_SYSCALL
-		if (dead_task->mm->context.ldt) {
-			pr_warn("WARNING: dead process %s still has LDT? <%p/%d>\n",
-				dead_task->comm,
-				dead_task->mm->context.ldt->entries,
-				dead_task->mm->context.ldt->nr_entries);
-			BUG();
-		}
-#endif
-	}
+	WARN_ON(dead_task->mm);
 }
 
 enum which_selector {