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Patch "drm/msm: fix use of copy_from_user() while holding spinlock" has been added to the 4.4-stable tree

PATCH [email protected] 1 participant 1 message Sep 9, 2016

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This is a note to let you know that I've just added the patch titled

drm/msm: fix use of copy_from_user() while holding spinlock

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drm-msm-fix-use-of-copy_from_user-while-holding-spinlock.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From 89f82cbb0d5c0ab768c8d02914188aa2211cd2e3 Mon Sep 17 00:00:00 2001

From: Rob Clark <[email protected]>
Date: Mon, 22 Aug 2016 15:15:23 -0400
Subject: drm/msm: fix use of copy_from_user() while holding spinlock

From: Rob Clark <[email protected]>

commit 89f82cbb0d5c0ab768c8d02914188aa2211cd2e3 upstream.

Use instead __copy_from_user_inatomic() and fallback to slow-path where we drop and re-aquire the lock in case of fault.

Reported-by Vaishali Thakkar <[email protected]>
Signed-off-by Rob Clark <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 drivers/gpu/drm/msm/msm_gem_submit.c |   27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)
drivers/gpu/drm/msm/msm_gem_submit.c +22 -5
@@ -55,6 +55,14 @@ static struct msm_gem_submit *submit_cre
 	return submit;
 }
 
+static inline unsigned long __must_check
+copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
+{
+	if (access_ok(VERIFY_READ, from, n))
+		return __copy_from_user_inatomic(to, from, n);
+	return -EFAULT;
+}
+
 static int submit_lookup_objects(struct msm_gem_submit *submit,
 		struct drm_msm_gem_submit *args, struct drm_file *file)
 {

@@ -62,6 +70,7 @@ static int submit_lookup_objects(struct
 	int ret = 0;
 
 	spin_lock(&file->table_lock);
+	pagefault_disable();
 
 	for (i = 0; i < args->nr_bos; i++) {
 		struct drm_msm_gem_submit_bo submit_bo;

@@ -70,10 +79,15 @@ static int submit_lookup_objects(struct
 		void __user *userptr =
 			to_user_ptr(args->bos + (i * sizeof(submit_bo)));
 
-		ret = copy_from_user(&submit_bo, userptr, sizeof(submit_bo));
-		if (ret) {
-			ret = -EFAULT;
-			goto out_unlock;
+		ret = copy_from_user_inatomic(&submit_bo, userptr, sizeof(submit_bo));
+		if (unlikely(ret)) {
+			pagefault_enable();
+			spin_unlock(&file->table_lock);
+			ret = copy_from_user(&submit_bo, userptr, sizeof(submit_bo));
+			if (ret)
+				goto out;
+			spin_lock(&file->table_lock);
+			pagefault_disable();
 		}
 
 		if (submit_bo.flags & ~MSM_SUBMIT_BO_FLAGS) {

@@ -113,9 +127,12 @@ static int submit_lookup_objects(struct
 	}
 
 out_unlock:
-	submit->nr_bos = i;
+	pagefault_enable();
 	spin_unlock(&file->table_lock);
 
+out:
+	submit->nr_bos = i;
+
 	return ret;
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/drm-msm-fix-use-of-copy_from_user-while-holding-spinlock.patch