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@xxxxxxxxxx>
---
fs/exec.c | 10 ++++++++++
include/linux/ksm.h | 13 +++++++++++++
2 files changed, 23 insertions(+)
diff --git a/fs/exec.c b/fs/exec.c
index ff6f26671cfc..66202d016a0a 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 +268,13 @@ static int __bprm_mm_init(struct linux_binprm *bprm)
goto err_free;
}
+ /*
+ * Need to be called with mmap write lock
+ * held, to avoid race with ksmd.
+ */
+ if (ksm_execve(mm))
+ goto err_ksm;
+
/*
* Place the stack at the largest stack address the architecture
* supports. Later, we'll move this to an appropriate place. We don't
@@ -288,6 +296,8 @@ static int __bprm_mm_init(struct linux_binprm *bprm)
bprm->p = vma->vm_end - sizeof(void *);
return 0;
err:
+ ksm_exit(mm);
+err_ksm:
mmap_write_unlock(mm);
err_free:
bprm->vma = NULL;
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
