Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

IB/mlx5: Fix potential deadlock in MR deregistration

The issue arises when kzalloc() is invoked while holding umem_mutex or any other lock acquired under umem_mutex. This is problematic because kzalloc() can trigger fs_reclaim_aqcuire(), which may, in turn, invoke mmu_notifier_invalidate_range_start(). This function can lead to mlx5_ib_invalidate_range(), which attempts to acquire umem_mutex again, resulting in a deadlock.

The problematic flow: CPU0 | CPU1 ---------------------------------------|------------------------------------------------ mlx5_ib_dereg_mr() | → revoke_mr() | → mutex_lock(&umem_odp->umem_mutex) | | mlx5_mkey_cache_init() | → mutex_lock(&dev->cache.rb_lock) | → mlx5r_cache_create_ent_locked() | → kzalloc(GFP_KERNEL) | → fs_reclaim() | → mmu_notifier_invalidate_range_start() | → mlx5_ib_invalidate_range() | → mutex_lock(&umem_odp->umem_mutex) → cache_ent_find_and_store() | → mutex_lock(&dev->cache.rb_lock) |

Additionally, when kzalloc(…