CVE-2022-50726 in Linux
Summary
by MITRE • 12/24/2025
In the Linux kernel, the following vulnerability has been resolved:
net/mlx5: Fix possible use-after-free in async command interface
mlx5_cmd_cleanup_async_ctx should return only after all its callback handlers were completed. Before this patch, the below race between mlx5_cmd_cleanup_async_ctx and mlx5_cmd_exec_cb_handler was possible and lead to a use-after-free:
1. mlx5_cmd_cleanup_async_ctx is called while num_inflight is 2 (i.e. elevated by 1, a single inflight callback). 2. mlx5_cmd_cleanup_async_ctx decreases num_inflight to 1. 3. mlx5_cmd_exec_cb_handler is called, decreases num_inflight to 0 and is about to call wake_up(). 4. mlx5_cmd_cleanup_async_ctx calls wait_event, which returns immediately as the condition (num_inflight == 0) holds. 5. mlx5_cmd_cleanup_async_ctx returns. 6. The caller of mlx5_cmd_cleanup_async_ctx frees the mlx5_async_ctx object. 7. mlx5_cmd_exec_cb_handler goes on and calls wake_up() on the freed object.
Fix it by syncing using a completion object. Mark it completed when num_inflight reaches 0.
Trace:
BUG: KASAN: use-after-free in do_raw_spin_lock+0x23d/0x270 Read of size 4 at addr ffff888139cd12f4 by task swapper/5/0
CPU: 5 PID: 0 Comm: swapper/5 Not tainted 6.0.0-rc3_for_upstream_debug_2022_08_30_13_10 #1 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 Call Trace: <IRQ> dump_stack_lvl+0x57/0x7d print_report.cold+0x2d5/0x684 ? do_raw_spin_lock+0x23d/0x270 kasan_report+0xb1/0x1a0 ? do_raw_spin_lock+0x23d/0x270 do_raw_spin_lock+0x23d/0x270 ? rwlock_bug.part.0+0x90/0x90 ? __delete_object+0xb8/0x100 ? lock_downgrade+0x6e0/0x6e0 _raw_spin_lock_irqsave+0x43/0x60 ? __wake_up_common_lock+0xb9/0x140 __wake_up_common_lock+0xb9/0x140 ? __wake_up_common+0x650/0x650 ? destroy_tis_callback+0x53/0x70 [mlx5_core]
? kasan_set_track+0x21/0x30 ? destroy_tis_callback+0x53/0x70 [mlx5_core]
? kfree+0x1ba/0x520 ? do_raw_spin_unlock+0x54/0x220 mlx5_cmd_exec_cb_handler+0x136/0x1a0 [mlx5_core]
? mlx5_cmd_cleanup_async_ctx+0x220/0x220 [mlx5_core]
? mlx5_cmd_cleanup_async_ctx+0x220/0x220 [mlx5_core]
mlx5_cmd_comp_handler+0x65a/0x12b0 [mlx5_core]
? dump_command+0xcc0/0xcc0 [mlx5_core]
? lockdep_hardirqs_on_prepare+0x400/0x400 ? cmd_comp_notifier+0x7e/0xb0 [mlx5_core]
cmd_comp_notifier+0x7e/0xb0 [mlx5_core]
atomic_notifier_call_chain+0xd7/0x1d0 mlx5_eq_async_int+0x3ce/0xa20 [mlx5_core]
atomic_notifier_call_chain+0xd7/0x1d0 ? irq_release+0x140/0x140 [mlx5_core]
irq_int_handler+0x19/0x30 [mlx5_core]
__handle_irq_event_percpu+0x1f2/0x620 handle_irq_event+0xb2/0x1d0 handle_edge_irq+0x21e/0xb00 __common_interrupt+0x79/0x1a0 common_interrupt+0x78/0xa0 </IRQ> <TASK> asm_common_interrupt+0x22/0x40 RIP: 0010:default_idle+0x42/0x60 Code: c1 83 e0 07 48 c1 e9 03 83 c0 03 0f b6 14 11 38 d0 7c 04 84 d2 75 14 8b 05 eb 47 22 02 85 c0 7e 07 0f 00 2d e0 9f 48 00 fb f4 <c3> 48 c7 c7 80 08 7f 85 e8 d1 d3 3e fe eb de 66 66 2e 0f 1f 84 00 RSP: 0018:ffff888100dbfdf0 EFLAGS: 00000242 RAX: 0000000000000001 RBX: ffffffff84ecbd48 RCX: 1ffffffff0afe110 RDX: 0000000000000004 RSI: 0000000000000000 RDI: ffffffff835cc9bc RBP: 0000000000000005 R08: 0000000000000001 R09: ffff88881dec4ac3 R10: ffffed1103bd8958 R11: 0000017d0ca571c9 R12: 0000000000000005 R13: ffffffff84f024e0 R14: 0000000000000000 R15: dffffc0000000000 ? default_idle_call+0xcc/0x450 default_idle_call+0xec/0x450 do_idle+0x394/0x450 ? arch_cpu_idle_exit+0x40/0x40 ? do_idle+0x17/0x450 cpu_startup_entry+0x19/0x20 start_secondary+0x221/0x2b0 ? set_cpu_sibling_map+0x2070/0x2070 secondary_startup_64_no_verify+0xcd/0xdb </TASK>
Allocated by task 49502: kasan_save_stack+0x1e/0x40 __kasan_kmalloc+0x81/0xa0 kvmalloc_node+0x48/0xe0 mlx5e_bulk_async_init+0x35/0x110 [mlx5_core]
mlx5e_tls_priv_tx_list_cleanup+0x84/0x3e0 [mlx5_core]
mlx5e_ktls_cleanup_tx+0x38f/0x760 [mlx5_core]
mlx5e_cleanup_nic_tx+0xa7/0x100 [mlx5_core]
mlx5e_detach_netdev+0x1c ---truncated---
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Analysis
by VulDB Data Team • 04/21/2026
The vulnerability described in CVE-2022-50726 resides within the Linux kernel's mlx5 driver, specifically in the asynchronous command interface handling mechanism. This flaw manifests as a use-after-free condition that can lead to system instability or potential exploitation. The issue is rooted in the mlx5_cmd_cleanup_async_ctx function which is responsible for cleaning up asynchronous command contexts. Prior to the patch, this function did not properly synchronize with callback handlers that might still be executing, creating a race condition where the cleanup process could prematurely free memory that was still in use by callback functions.
The race condition occurs during the interaction between mlx5_cmd_cleanup_async_ctx and mlx5_cmd_exec_cb_handler functions. When cleanup begins with num_inflight set to 2, the context decreases this counter to 1. However, a callback handler may simultaneously execute, reducing the counter to 0 and preparing to call wake_up(). The cleanup function then proceeds to wait_event and returns immediately upon the condition num_inflight == 0 being satisfied, even though the callback handler has not yet completed execution. This premature return allows the caller to free the mlx5_async_ctx object, while the callback handler continues execution and attempts to access the freed memory, resulting in a use-after-free error.
This vulnerability directly maps to CWE-416, which describes the use of freed memory condition, and aligns with ATT&CK technique T1059.001 for command and scripting interpreter. The kernel's memory management and synchronization mechanisms fail to prevent concurrent access patterns that lead to memory corruption. The KASAN (Kernel Address Sanitizer) report indicates that the issue occurs during a spin lock operation, suggesting that the race condition involves low-level synchronization primitives and memory access patterns typical of kernel-level concurrency issues.
The fix implemented addresses this by introducing proper synchronization using a completion object that marks the completion only when num_inflight reaches zero. This ensures that mlx5_cmd_cleanup_async_ctx waits for all callback handlers to complete before proceeding with cleanup, preventing the premature deallocation of memory. The patch follows established kernel development practices for handling asynchronous operations and memory lifecycle management. This type of vulnerability represents a critical security concern in kernel space as it can potentially allow privilege escalation or system crashes. The fix ensures proper ordering and synchronization between asynchronous callback execution and cleanup operations, thereby maintaining the integrity of kernel memory management and preventing unauthorized access patterns. Organizations should apply the relevant kernel updates immediately to mitigate this vulnerability and protect against potential exploitation through malicious network traffic or system operations that trigger the affected code path.