6.18-stable review patch. If anyone has any objections, please let me know.
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From: Xiao Ni xni@redhat.com
[ Upstream commit 90e3bb44c0a86e245d8e5c6520206fa113acb1ee ]
There is a uaf problem which is found by case 23rdev-lifetime:
Oops: general protection fault, probably for non-canonical address 0xdead000000000122 RIP: 0010:bdi_unregister+0x4b/0x170 Call Trace: <TASK> __del_gendisk+0x356/0x3e0 mddev_unlock+0x351/0x360 rdev_attr_store+0x217/0x280 kernfs_fop_write_iter+0x14a/0x210 vfs_write+0x29e/0x550 ksys_write+0x74/0xf0 do_syscall_64+0xbb/0x380 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7ff5250a177e
The sequence is: 1. rdev remove path gets reconfig_mutex 2. rdev remove path release reconfig_mutex in mddev_unlock 3. md stop calls do_md_stop and sets MD_DELETED 4. rdev remove path calls del_gendisk because MD_DELETED is set 5. md stop path release reconfig_mutex and calls del_gendisk again
So there is a race condition we should resolve. This patch adds a flag MD_DO_DELETE to avoid the race condition.
Link: https://lore.kernel.org/linux-raid/20251029063419.21700-1-xni@redhat.com Fixes: 9e59d609763f ("md: call del_gendisk in control path") Signed-off-by: Xiao Ni xni@redhat.com Suggested-by: Yu Kuai yukuai@fnnas.com Reviewed-by: Li Nan linan122@huawei.com Signed-off-by: Yu Kuai yukuai@fnnas.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/md/md.c | 3 ++- drivers/md/md.h | 1 + 2 files changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/md/md.c b/drivers/md/md.c index 6062e0deb6160..5d40beaecc9c7 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -941,7 +941,8 @@ void mddev_unlock(struct mddev *mddev) * do_md_stop. dm raid only uses md_stop to stop. So dm raid * doesn't need to check MD_DELETED when getting reconfig lock */ - if (test_bit(MD_DELETED, &mddev->flags)) { + if (test_bit(MD_DELETED, &mddev->flags) && + !test_and_set_bit(MD_DO_DELETE, &mddev->flags)) { kobject_del(&mddev->kobj); del_gendisk(mddev->gendisk); } diff --git a/drivers/md/md.h b/drivers/md/md.h index 5d5f780b84477..fd6e001c1d38f 100644 --- a/drivers/md/md.h +++ b/drivers/md/md.h @@ -354,6 +354,7 @@ enum mddev_flags { MD_HAS_MULTIPLE_PPLS, MD_NOT_READY, MD_BROKEN, + MD_DO_DELETE, MD_DELETED, };