FAILED: patch "[PATCH] component: do not leave master devres group open after bind" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From c87761db2100677a69be551365105125d872af5b Mon Sep 17 00:00:00 2001
From: Kai Vehmanen <[email protected]>
Date: Wed, 13 Oct 2021 19:13:45 +0300
Subject: [PATCH] component: do not leave master devres group open after bind

In current code, the devres group for aggregate master is left open after call to component_master_add_*(). This leads to problems when the master does further managed allocations on its own. When any participating driver calls component_del(), this leads to immediate release of resources.

This came up when investigating a page fault occurring with i915 DRM driver unbind with 5.15-rc1 kernel. The following sequence occurs:

i915_pci_remove()
-> intel_display_driver_unregister()

     -> i915_audio_component_cleanup()
       -> component_del()
         -> component.c:take_down_master()
           -> hdac_component_master_unbind() [via master->ops->unbind()]
           -> devres_release_group(master->parent, NULL)

With older kernels this has not caused issues, but with audio driver moving to use managed interfaces for more of its allocations, this no longer works. Devres log shows following to occur:

component_master_add_with_match()

[  126.886032] snd_hda_intel 0000:00:1f.3: DEVRES ADD 00000000323ccdc5 devm_component_match_release (24 bytes)
[  126.886045] snd_hda_intel 0000:00:1f.3: DEVRES ADD 00000000865cdb29 grp< (0 bytes)
[  126.886049] snd_hda_intel 0000:00:1f.3: DEVRES ADD 000000001b480725 grp< (0 bytes)

audio driver completes its PCI probe()

[  126.892238] snd_hda_intel 0000:00:1f.3: DEVRES ADD 000000001b480725 pcim_iomap_release (48 bytes)

component_del() called() at DRM/i915 unbind()

[  137.579422] i915 0000:00:02.0: DEVRES REL 00000000ef44c293 grp< (0 bytes)
[  137.579445] snd_hda_intel 0000:00:1f.3: DEVRES REL 00000000865cdb29 grp< (0 bytes)
[  137.579458] snd_hda_intel 0000:00:1f.3: DEVRES REL 000000001b480725 pcim_iomap_release (48 bytes)

So the "devres_release_group(master->parent, NULL)" ends up freeing the pcim_iomap allocation. Upon next runtime resume, the audio driver will cause a page fault as the iomap alloc was released without the driver knowing about it.

Fix this issue by using the "struct master" pointer as identifier for the devres group, and by closing the devres group after
the master->ops->bind() call is done. This allows devres allocations done by the driver acting as master to be isolated from the binding state of the aggregate driver. This modifies the logic originally introduced in commit 9e1ccb4a7700 ("drivers/base: fix devres handling for master device")

index 6dc309913ccd..2d25a6416587 100644
@@ -245,7 +245,7 @@ static int try_to_bring_up_master(struct master *master,
 		return 0;
 	}
 
-	if (!devres_open_group(master->parent, NULL, GFP_KERNEL))
+	if (!devres_open_group(master->parent, master, GFP_KERNEL))
 		return -ENOMEM;
 
 	/* Found all components */

@@ -257,6 +257,7 @@ static int try_to_bring_up_master(struct master *master,
 		return ret;
 	}
 
+	devres_close_group(master->parent, NULL);
 	master->bound = true;
 	return 1;
 }

@@ -281,7 +282,7 @@ static void take_down_master(struct master *master)
 {
 	if (master->bound) {
 		master->ops->unbind(master->parent);
-		devres_release_group(master->parent, NULL);
+		devres_release_group(master->parent, master);
 		master->bound = false;
 	}
 }