FAILED: patch "[PATCH] rust: block: fix GenDisk cleanup paths" failed to apply to 6.12-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.12-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 <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 2957771379fa335103a4b539db57bb2271e12142
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026070953-laurel-zeppelin-239b@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From 2957771379fa335103a4b539db57bb2271e12142 Mon Sep 17 00:00:00 2001
From: Haoze Xie <royenheart@gmail.com>
Date: Sat, 30 May 2026 14:11:54 +0800
Subject: [PATCH] rust: block: fix GenDisk cleanup paths

GenDiskBuilder::build() still has fallible work after
__blk_mq_alloc_disk(), but its error path only recovers the
foreign queue data. That leaks the temporary gendisk and
request_queue until later teardown. If the caller moved the last
Arc<TagSet<T>> into build(), the leaked queue can retain blk-mq
state after the tag set is dropped.

Fix the pre-registration failure path by dropping the temporary
gendisk reference with put_disk() before recovering queue_data,
so disk_release() can tear down the owned queue.

Also pair GenDisk::drop() with put_disk() after del_gendisk().
Once a Rust GenDisk has been added with device_add_disk(),
del_gendisk() only unregisters it; the final gendisk reference
still has to be dropped to complete the release path.

Fixes: 3253aba3408a ("rust: block: introduce `kernel::block::mq` module")
Cc: stable@kernel.org
Reported-by: Yuan Tan <yuantan098@gmail.com>
Reported-by: Xin Liu <bird@lzu.edu.cn>
Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: Haoze Xie <royenheart@gmail.com>
Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
Link: https://patch.msgid.link/b70aff9a920cc42110fe5cf454c3099561863519.1780063368.git.royenheart@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/rust/kernel/block/mq/gen_disk.rs b/rust/kernel/block/mq/gen_disk.rs
index 912cb805caf5..fc97dd873974 100644
--- a/rust/kernel/block/mq/gen_disk.rs
+++ b/rust/kernel/block/mq/gen_disk.rs
@@ -150,6 +150,19 @@ pub fn build<T: Operations>(
         // SAFETY: `gendisk` is a valid pointer as we initialized it above
         unsafe { (*gendisk).fops = &TABLE };
 
+        let cleanup_failure = ScopeGuard::new_with_data((gendisk, data), |(gendisk, data)| {
+            // SAFETY: `gendisk` came from `__blk_mq_alloc_disk()` above and
+            // has not been added to the VFS on this cleanup path.
+            unsafe { bindings::put_disk(gendisk) };
+            // SAFETY: `data` came from `into_foreign()` above and has not been
+            // converted back on this cleanup path.
+            drop(unsafe { T::QueueData::from_foreign(data) });
+        });
+
+        // The failure guard now owns both pieces of cleanup; the early guard
+        // must not run on this path anymore.
+        recover_data.dismiss();
+
         let mut writer = NullTerminatedFormatter::new(
             // SAFETY: `gendisk` points to a valid and initialized instance. We
             // have exclusive access, since the disk is not added to the VFS
@@ -172,7 +185,7 @@ pub fn build<T: Operations>(
             },
         )?;
 
-        recover_data.dismiss();
+        cleanup_failure.dismiss();
 
         // INVARIANT: `gendisk` was initialized above.
         // INVARIANT: `gendisk` was added to the VFS via `device_add_disk` above.
@@ -215,6 +228,11 @@ fn drop(&mut self) {
         // to the VFS.
         unsafe { bindings::del_gendisk(self.gendisk) };
 
+        // SAFETY: By type invariant, `self.gendisk` was added to the VFS, so
+        // `put_disk()` must follow `del_gendisk()` to drop the final gendisk
+        // reference and trigger the remaining release path.
+        unsafe { bindings::put_disk(self.gendisk) };
+
         // SAFETY: `queue.queuedata` was created by `GenDiskBuilder::build` with
         // a call to `ForeignOwnable::into_foreign` to create `queuedata`.
         // `ForeignOwnable::from_foreign` is only called here.