Allow userfaultfd monitor track termination of the processes that have
memory backed by the uffd.
Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
Acked-by: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx>
---
fs/userfaultfd.c | 24 ++++++++++++++++++++++++
include/linux/userfaultfd_k.h | 7 +++++++
include/uapi/linux/userfaultfd.h | 5 ++++-
kernel/exit.c | 2 ++
4 files changed, 37 insertions(+), 1 deletion(-)
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 651d6d8..839ffd5 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -774,6 +774,30 @@ void userfaultfd_unmap_complete(struct mm_struct *mm, struct list_head *uf)
}
}
+void userfaultfd_exit(struct mm_struct *mm)
+{
+ struct vm_area_struct *vma = mm->mmap;
+
+ while (vma) {
+ struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx;
+
+ if (ctx && (ctx->features & UFFD_FEATURE_EVENT_EXIT)) {
+ struct userfaultfd_wait_queue ewq;
+
+ userfaultfd_ctx_get(ctx);
+
+ msg_init(&ewq.msg);
+ ewq.msg.event = UFFD_EVENT_EXIT;
+
+ userfaultfd_event_wait_completion(ctx, &ewq);
+
+ ctx->features &= ~UFFD_FEATURE_EVENT_EXIT;
+ }
+
+ vma = vma->vm_next;
+ }
+}
+
static int userfaultfd_release(struct inode *inode, struct file *file)
{
struct userfaultfd_ctx *ctx = file->private_data;
diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index a40be5d..0468548 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -72,6 +72,8 @@ extern int userfaultfd_unmap_prep(struct vm_area_struct *vma,
extern void userfaultfd_unmap_complete(struct mm_struct *mm,
struct list_head *uf);
+extern void userfaultfd_exit(struct mm_struct *mm);
+
#else /* CONFIG_USERFAULTFD */
/* mm helpers */
@@ -136,6 +138,11 @@ static inline void userfaultfd_unmap_complete(struct mm_struct *mm,
struct list_head *uf)
{
}
+
+static inline void userfaultfd_exit(struct mm_struct *mm)
+{
+}
+
#endif /* CONFIG_USERFAULTFD */
#endif /* _LINUX_USERFAULTFD_K_H */
diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h
index 3b05953..c055947 100644
--- a/include/uapi/linux/userfaultfd.h
+++ b/include/uapi/linux/userfaultfd.h
@@ -18,7 +18,8 @@
* means the userland is reading).
*/
#define UFFD_API ((__u64)0xAA)
-#define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_FORK | \
+#define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_EXIT | \
+ UFFD_FEATURE_EVENT_FORK | \
UFFD_FEATURE_EVENT_REMAP | \
UFFD_FEATURE_EVENT_REMOVE | \
UFFD_FEATURE_EVENT_UNMAP | \
@@ -112,6 +113,7 @@ struct uffd_msg {
#define UFFD_EVENT_REMAP 0x14
#define UFFD_EVENT_REMOVE 0x15
#define UFFD_EVENT_UNMAP 0x16
+#define UFFD_EVENT_EXIT 0x17
/* flags for UFFD_EVENT_PAGEFAULT */
#define UFFD_PAGEFAULT_FLAG_WRITE (1<<0) /* If this was a write fault */
@@ -161,6 +163,7 @@ struct uffdio_api {
#define UFFD_FEATURE_MISSING_HUGETLBFS (1<<4)
#define UFFD_FEATURE_MISSING_SHMEM (1<<5)
#define UFFD_FEATURE_EVENT_UNMAP (1<<6)
+#define UFFD_FEATURE_EVENT_EXIT (1<<7)
__u64 features;
__u64 ioctls;
diff --git a/kernel/exit.c b/kernel/exit.c
index 16c6077..c11bf9d 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -55,6 +55,7 @@
#include <linux/kcov.h>
#include <linux/random.h>
#include <linux/rcuwait.h>
+#include <linux/userfaultfd_k.h>
#include <linux/uaccess.h>
#include <asm/unistd.h>
@@ -547,6 +548,7 @@ static void exit_mm(void)
enter_lazy_tlb(mm, current);
task_unlock(current);
mm_update_next_owner(mm);
+ userfaultfd_exit(mm);
mmput(mm);
if (test_thread_flag(TIF_MEMDIE))
exit_oom_victim();
--
1.9.1
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