[PATCH v3] mm/ksm: fix ksm exec support for prctl

[Jinjiang Tu <tujinjiang@huawei.com>]

commit 3c6f33b7273a ("mm/ksm: support fork/exec for prctl") inherits
MMF_VM_MERGE_ANY flag when a task calls execve(). Howerver, it doesn't
create the mm_slot, so ksmd will not try to scan this task.

To fix it, allocate and add the mm_slot to ksm_mm_head in __bprm_mm_init()
when the mm has MMF_VM_MERGE_ANY flag.

Fixes: 3c6f33b7273a ("mm/ksm: support fork/exec for prctl")
Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com>
---
 fs/exec.c           |  4 ++++
 include/linux/ksm.h | 13 +++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/fs/exec.c b/fs/exec.c
index ff6f26671cfc..00f40163cc12 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -67,6 +67,7 @@
 #include <linux/time_namespace.h>
 #include <linux/user_events.h>
 #include <linux/rseq.h>
+#include <linux/ksm.h>
 
 #include <linux/uaccess.h>
 #include <asm/mmu_context.h>
@@ -267,6 +268,9 @@ static int __bprm_mm_init(struct linux_binprm *bprm)
 		goto err_free;
 	}
 
+	if (ksm_execve(mm))
+		goto err;
+
 	/*
 	 * Place the stack at the largest stack address the architecture
 	 * supports. Later, we'll move this to an appropriate place. We don't
diff --git a/include/linux/ksm.h b/include/linux/ksm.h
index 401348e9f92b..7e2b1de3996a 100644
--- a/include/linux/ksm.h
+++ b/include/linux/ksm.h
@@ -59,6 +59,14 @@ static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
 	return 0;
 }
 
+static inline int ksm_execve(struct mm_struct *mm)
+{
+	if (test_bit(MMF_VM_MERGE_ANY, &mm->flags))
+		return __ksm_enter(mm);
+
+	return 0;
+}
+
 static inline void ksm_exit(struct mm_struct *mm)
 {
 	if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
@@ -107,6 +115,11 @@ static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
 	return 0;
 }
 
+static inline int ksm_execve(struct mm_struct *mm)
+{
+	return 0;
+}
+
 static inline void ksm_exit(struct mm_struct *mm)
 {
 }
-- 
2.25.1