ghsa-4fj4-ghwr-gjf7
Vulnerability from github
Published
2025-02-27 21:32
Modified
2025-03-05 15:30
Severity ?
5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Details

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

rxrpc, afs: Fix peer hash locking vs RCU callback

In its address list, afs now retains pointers to and refs on one or more rxrpc_peer objects. The address list is freed under RCU and at this time, it puts the refs on those peers.

Now, when an rxrpc_peer object runs out of refs, it gets removed from the peer hash table and, for that, rxrpc has to take a spinlock. However, it is now being called from afs's RCU cleanup, which takes place in BH context - but it is just taking an ordinary spinlock.

The put may also be called from non-BH context, and so there exists the possibility of deadlock if the BH-based RCU cleanup happens whilst the hash spinlock is held. This led to the attached lockdep complaint.

Fix this by changing spinlocks of rxnet->peer_hash_lock back to BH-disabling locks.

================================
WARNING: inconsistent lock state
6.13.0-rc5-build2+ #1223 Tainted: G            E
--------------------------------
inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
swapper/1/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
ffff88810babe228 (&rxnet->peer_hash_lock){+.?.}-{3:3}, at: rxrpc_put_peer+0xcb/0x180
{SOFTIRQ-ON-W} state was registered at:
  mark_usage+0x164/0x180
  __lock_acquire+0x544/0x990
  lock_acquire.part.0+0x103/0x280
  _raw_spin_lock+0x2f/0x40
  rxrpc_peer_keepalive_worker+0x144/0x440
  process_one_work+0x486/0x7c0
  process_scheduled_works+0x73/0x90
  worker_thread+0x1c8/0x2a0
  kthread+0x19b/0x1b0
  ret_from_fork+0x24/0x40
  ret_from_fork_asm+0x1a/0x30
irq event stamp: 972402
hardirqs last  enabled at (972402): [<ffffffff8244360e>] _raw_spin_unlock_irqrestore+0x2e/0x50
hardirqs last disabled at (972401): [<ffffffff82443328>] _raw_spin_lock_irqsave+0x18/0x60
softirqs last  enabled at (972300): [<ffffffff810ffbbe>] handle_softirqs+0x3ee/0x430
softirqs last disabled at (972313): [<ffffffff810ffc54>] __irq_exit_rcu+0x44/0x110

other info that might help us debug this:
 Possible unsafe locking scenario:
       CPU0
       ----
  lock(&rxnet->peer_hash_lock);
  <Interrupt>
    lock(&rxnet->peer_hash_lock);

 *** DEADLOCK ***
1 lock held by swapper/1/0:
 #0: ffffffff83576be0 (rcu_callback){....}-{0:0}, at: rcu_lock_acquire+0x7/0x30

stack backtrace:
CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Tainted: G            E      6.13.0-rc5-build2+ #1223
Tainted: [E]=UNSIGNED_MODULE
Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014
Call Trace:
 <IRQ>
 dump_stack_lvl+0x57/0x80
 print_usage_bug.part.0+0x227/0x240
 valid_state+0x53/0x70
 mark_lock_irq+0xa5/0x2f0
 mark_lock+0xf7/0x170
 mark_usage+0xe1/0x180
 __lock_acquire+0x544/0x990
 lock_acquire.part.0+0x103/0x280
 _raw_spin_lock+0x2f/0x40
 rxrpc_put_peer+0xcb/0x180
 afs_free_addrlist+0x46/0x90 [kafs]
 rcu_do_batch+0x2d2/0x640
 rcu_core+0x2f7/0x350
 handle_softirqs+0x1ee/0x430
 __irq_exit_rcu+0x44/0x110
 irq_exit_rcu+0xa/0x30
 sysvec_apic_timer_interrupt+0x7f/0xa0
 </IRQ>
Show details on source website

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{
  "affected": [],
  "aliases": [
    "CVE-2025-21809"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-667"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-02-27T20:16:03Z",
    "severity": "MODERATE"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nrxrpc, afs: Fix peer hash locking vs RCU callback\n\nIn its address list, afs now retains pointers to and refs on one or more\nrxrpc_peer objects.  The address list is freed under RCU and at this time,\nit puts the refs on those peers.\n\nNow, when an rxrpc_peer object runs out of refs, it gets removed from the\npeer hash table and, for that, rxrpc has to take a spinlock.  However, it\nis now being called from afs\u0027s RCU cleanup, which takes place in BH\ncontext - but it is just taking an ordinary spinlock.\n\nThe put may also be called from non-BH context, and so there exists the\npossibility of deadlock if the BH-based RCU cleanup happens whilst the hash\nspinlock is held.  This led to the attached lockdep complaint.\n\nFix this by changing spinlocks of rxnet-\u003epeer_hash_lock back to\nBH-disabling locks.\n\n    ================================\n    WARNING: inconsistent lock state\n    6.13.0-rc5-build2+ #1223 Tainted: G            E\n    --------------------------------\n    inconsistent {SOFTIRQ-ON-W} -\u003e {IN-SOFTIRQ-W} usage.\n    swapper/1/0 [HC0[0]:SC1[1]:HE1:SE0] takes:\n    ffff88810babe228 (\u0026rxnet-\u003epeer_hash_lock){+.?.}-{3:3}, at: rxrpc_put_peer+0xcb/0x180\n    {SOFTIRQ-ON-W} state was registered at:\n      mark_usage+0x164/0x180\n      __lock_acquire+0x544/0x990\n      lock_acquire.part.0+0x103/0x280\n      _raw_spin_lock+0x2f/0x40\n      rxrpc_peer_keepalive_worker+0x144/0x440\n      process_one_work+0x486/0x7c0\n      process_scheduled_works+0x73/0x90\n      worker_thread+0x1c8/0x2a0\n      kthread+0x19b/0x1b0\n      ret_from_fork+0x24/0x40\n      ret_from_fork_asm+0x1a/0x30\n    irq event stamp: 972402\n    hardirqs last  enabled at (972402): [\u003cffffffff8244360e\u003e] _raw_spin_unlock_irqrestore+0x2e/0x50\n    hardirqs last disabled at (972401): [\u003cffffffff82443328\u003e] _raw_spin_lock_irqsave+0x18/0x60\n    softirqs last  enabled at (972300): [\u003cffffffff810ffbbe\u003e] handle_softirqs+0x3ee/0x430\n    softirqs last disabled at (972313): [\u003cffffffff810ffc54\u003e] __irq_exit_rcu+0x44/0x110\n\n    other info that might help us debug this:\n     Possible unsafe locking scenario:\n           CPU0\n           ----\n      lock(\u0026rxnet-\u003epeer_hash_lock);\n      \u003cInterrupt\u003e\n        lock(\u0026rxnet-\u003epeer_hash_lock);\n\n     *** DEADLOCK ***\n    1 lock held by swapper/1/0:\n     #0: ffffffff83576be0 (rcu_callback){....}-{0:0}, at: rcu_lock_acquire+0x7/0x30\n\n    stack backtrace:\n    CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Tainted: G            E      6.13.0-rc5-build2+ #1223\n    Tainted: [E]=UNSIGNED_MODULE\n    Hardware name: ASUS All Series/H97-PLUS, BIOS 2306 10/09/2014\n    Call Trace:\n     \u003cIRQ\u003e\n     dump_stack_lvl+0x57/0x80\n     print_usage_bug.part.0+0x227/0x240\n     valid_state+0x53/0x70\n     mark_lock_irq+0xa5/0x2f0\n     mark_lock+0xf7/0x170\n     mark_usage+0xe1/0x180\n     __lock_acquire+0x544/0x990\n     lock_acquire.part.0+0x103/0x280\n     _raw_spin_lock+0x2f/0x40\n     rxrpc_put_peer+0xcb/0x180\n     afs_free_addrlist+0x46/0x90 [kafs]\n     rcu_do_batch+0x2d2/0x640\n     rcu_core+0x2f7/0x350\n     handle_softirqs+0x1ee/0x430\n     __irq_exit_rcu+0x44/0x110\n     irq_exit_rcu+0xa/0x30\n     sysvec_apic_timer_interrupt+0x7f/0xa0\n     \u003c/IRQ\u003e",
  "id": "GHSA-4fj4-ghwr-gjf7",
  "modified": "2025-03-05T15:30:51Z",
  "published": "2025-02-27T21:32:16Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-21809"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0e77dd41689637ac4e1b8fe0f27541f373640855"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/10ba5a3d57af20e494e0d979d1894260989235dd"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/79d458c13056559d49b5e41fbc4b6890e68cf65b"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}


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