This is a note to let you know that I've just added the patch titled
drm/shmem-helper: Avoid vm_open error paths
to the 5.15-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-shmem-helper-avoid-vm_open-error-paths.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 09bf649a74573cb596e211418a4f8008f265c5a9 Mon Sep 17 00:00:00 2001
From: Rob Clark <robdclark@xxxxxxxxxxxx>
Date: Wed, 30 Nov 2022 10:57:48 -0800
Subject: drm/shmem-helper: Avoid vm_open error paths
From: Rob Clark <robdclark@xxxxxxxxxxxx>
commit 09bf649a74573cb596e211418a4f8008f265c5a9 upstream.
vm_open() is not allowed to fail. Fortunately we are guaranteed that
the pages are already pinned, thanks to the initial mmap which is now
being cloned into a forked process, and only need to increment the
refcnt. So just increment it directly. Previously if a signal was
delivered at the wrong time to the forking process, the
mutex_lock_interruptible() could fail resulting in the pages_use_count
not being incremented.
Fixes: 2194a63a818d ("drm: Add library for shmem backed GEM objects")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Signed-off-by: Javier Martinez Canillas <javierm@xxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20221130185748.357410-3-robdclark@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/drm_gem_shmem_helper.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -541,12 +541,20 @@ static void drm_gem_shmem_vm_open(struct
{
struct drm_gem_object *obj = vma->vm_private_data;
struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
- int ret;
WARN_ON(shmem->base.import_attach);
- ret = drm_gem_shmem_get_pages(shmem);
- WARN_ON_ONCE(ret != 0);
+ mutex_lock(&shmem->pages_lock);
+
+ /*
+ * We should have already pinned the pages when the buffer was first
+ * mmap'd, vm_open() just grabs an additional reference for the new
+ * mm the vma is getting copied into (ie. on fork()).
+ */
+ if (!WARN_ON_ONCE(!shmem->pages_use_count))
+ shmem->pages_use_count++;
+
+ mutex_unlock(&shmem->pages_lock);
drm_gem_vm_open(vma);
}
Patches currently in stable-queue which might be from robdclark@xxxxxxxxxxxx are
queue-5.15/drm-shmem-helper-remove-errant-put-in-error-path.patch
queue-5.15/drm-shmem-helper-avoid-vm_open-error-paths.patch
