linux-kernel - [PATCH 5.11 297/329] xen/gntdev: fix gntdev

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Date:   Mon, 17 May 2021 16:03:28 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Marek Marczykowski-Górecki 
        <marmarek@...isiblethingslab.com>, Juergen Gross <jgross@...e.com>,
        Luca Fancellu <luca.fancellu@....com>
Subject: [PATCH 5.11 297/329] xen/gntdev: fix gntdev_mmap() error exit path

From: Juergen Gross <jgross@...e.com>

commit 970655aa9b42461f8394e4457307005bdeee14d9 upstream.

Commit d3eeb1d77c5d0af ("xen/gntdev: use mmu_interval_notifier_insert")
introduced an error in gntdev_mmap(): in case the call of
mmu_interval_notifier_insert_locked() fails the exit path should not
call mmu_interval_notifier_remove(), as this might result in NULL
dereferences.

One reason for failure is e.g. a signal pending for the running
process.

Fixes: d3eeb1d77c5d0af ("xen/gntdev: use mmu_interval_notifier_insert")
Cc: stable@...r.kernel.org
Reported-by: Marek Marczykowski-Górecki <marmarek@...isiblethingslab.com>
Tested-by: Marek Marczykowski-Górecki <marmarek@...isiblethingslab.com>
Signed-off-by: Juergen Gross <jgross@...e.com>
Reviewed-by: Luca Fancellu <luca.fancellu@....com>
Link: https://lore.kernel.org/r/20210423054038.26696-1-jgross@suse.com
Signed-off-by: Juergen Gross <jgross@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/xen/gntdev.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -1005,8 +1005,10 @@ static int gntdev_mmap(struct file *flip
 		err = mmu_interval_notifier_insert_locked(
 			&map->notifier, vma->vm_mm, vma->vm_start,
 			vma->vm_end - vma->vm_start, &gntdev_mmu_ops);
-		if (err)
+		if (err) {
+			map->vma = NULL;
 			goto out_unlock_put;
+		}
 	}
 	mutex_unlock(&priv->lock);