CVE-2023-52587 Information

Mar 07, 2024 cve

Description

In the Linux kernel the following vulnerability has been resolved:

IB/ipoib: Fix mcast list locking

Releasing the priv->lock while iterating the priv->multicast_list in ipoib_mcast_join_task() opens a window for ipoib_mcast_dev_flush() to remove the items while in the middle of iteration. If the mcast is removed while the lock was dropped the for loop spins forever resulting in a hard lockup (as was reported on RHEL 4.18.0-372.75.1.el8_6 kernel):

Task A (kworker/u72:2 below)       | Task B (kworker/u72:0 below)
-----------------------------------+-----------------------------------
ipoib_mcast_join_task(work)        | ipoib_ib_dev_flush_light(work)
  spin_lock_irq(&priv->lock)       | __ipoib_ib_dev_flush(priv ...)
  list_for_each_entry(mcast       | ipoib_mcast_dev_flush(dev = priv->dev)
      &priv->multicast_list list) |
    ipoib_mcast_join(dev mcast)   |
      spin_unlock_irq(&priv->lock) |
                                   |   spin_lock_irqsave(&priv->lock flags)
                                   |   list_for_each_entry_safe(mcast tmcast
                                   |                  &priv->multicast_list list)
                                   |     list_del(&mcast->list);
                                   |     list_add_tail(&mcast->list &remove_list)
                                   |   spin_unlock_irqrestore(&priv->lock flags)
      spin_lock_irq(&priv->lock)   |
                                   |   ipoib_mcast_remove_list(&remove_list)

(Here mcast is no longer on the | list_for_each_entry_safe(mcast tmcast priv->multicast_list and we keep | remove_list list) spinning on the remove_list of | »> wait_for_completion(&mcast->done) the other thread which is blocked | and the list is still valid on | it’s stack.)

Fix this by keeping the lock held and changing to GFP_ATOMIC to prevent eventual sleeps. Unfortunately we could not reproduce the lockup and confirm this fix but based on the code review I think this fix should address such lockups.

crash> bc 31 PID: 747 TASK: ff1c6a1a007e8000 CPU: 31 COMMAND: \kworker/u72:2\n– [exception RIP: ipoib_mcast_join_task+0x1b1] RIP: ffffffffc0944ac1 RSP: ff646f199a8c7e00 RFLAGS: 00000002 RAX: 0000000000000000 RBX: ff1c6a1a04dc82f8 RCX: 0000000000000000 work (&priv->mcast_task.work) RDX: ff1c6a192d60ac68 RSI: 0000000000000286 RDI: ff1c6a1a04dc8000 &mcast->list RBP: ff646f199a8c7e90 R8: ff1c699980019420 R9: ff1c6a1920c9a000 R10: ff646f199a8c7e00 R11: ff1c6a191a7d9800 R12: ff1c6a192d60ac00 mcast R13: ff1c6a1d82200000 R14: ff1c6a1a04dc8000 R15: ff1c6a1a04dc82d8 dev priv (&priv->lock) &priv->multicast_list (aka head) ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 — — 5 [ff646f199a8c7e00] ipoib_mcast_join_task+0x1b1 at ffffffffc0944ac1 [ib_ipoib] 6 [ff646f199a8c7e98] process_one_work+0x1a7 at ffffffff9bf10967

crash> rx ff646f199a8c7e68 ff646f199a8c7e68: ff1c6a1a04dc82f8 «< work = &priv->mcast_task.work

crash> list -hO ipoib_dev_priv.multicast_list ff1c6a1a04dc8000 (empty)

crash> ipoib_dev_priv.mcast_task.work.funcmcast_mutex.owner.counter ff1c6a1a04dc8000 mcast_task.work.func = 0xffffffffc0944910 <ipoib_mcast_join_task> mcast_mutex.owner.counter = 0xff1c69998efec000

crash> b 8 PID: 8 TASK: ff1c69998efec000 CPU: 33 COMMAND: \kworker/u72:0\n– 3 [ff646f1980153d50] wait_for_completion+0x96 at ffffffff9c7d7646 4 [ff646f1980153d90] ipoib_mcast_remove_list+0x56 at ffffffffc0944dc6 [ib_ipoib] 5 [ff646f1980153de8] ipoib_mcast_dev_flush+0x1a7 at ffffffffc09455a7 [ib_ipoib] 6 [ff646f1980153e58] __ipoib_ib_dev_flush+0x1a4 at ffffffffc09431a4 [ib_ipoib] 7 [ff

truncated—

Reference

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