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

gpio: eic-sprd: use raw_spinlock_t in the irq startup path

sprd_eic_irq_unmask() enables the GPIO IRQ and then updates controller
state through sprd_eic_update(), which takes sprd_eic->lock with
spin_lock_irqsave().  The callback can be reached from irq_startup()
while setting up a requested IRQ.  That path is not sleepable, but on
PREEMPT_RT a regular spinlock_t becomes a sleeping lock.

This issue was found by our static analysis tool and then manually
reviewed against the current tree.

The grounded PoC kept the request_threaded_irq() -> __setup_irq() ->
irq_startup() -> sprd_eic_irq_unmask() -> sprd_eic_update() carrier and
used the original spin_lock_irqsave(&sprd_eic->lock) edge.  Lockdep

  BUG: sleeping function called from invalid context
  hardirqs last disabled at ... __setup_irq.constprop.0 ... [vuln_msv]
  sprd_rt_spin_lock_irqsave+0x1c/0x30 [vuln_msv]
  sprd_eic_update.constprop.0+0x48/0x90 [vuln_msv]
  sprd_eic_irq_unmask.constprop.0+0x35/0x50 [vuln_msv]
  __setup_irq.constprop.0+0xd/0x30 [vuln_msv]

Convert the Spreadtrum EIC controller lock to raw_spinlock_t.  The
locked section only serializes MMIO register updates and does not contain
sleepable operations, so keeping it non-sleeping is appropriate for the
irqchip callbacks.

https://git.kernel.org/stable/c/19d63fd528719ce7d06d9aeb88d25b7d6478198a

https://git.kernel.org/stable/c/4750909a40da9016185e0ac991510a278cecb1e7

https://git.kernel.org/stable/c/581ac2ad001ff1128931191f249a7f2074672b7a

https://git.kernel.org/stable/c/5c3c9ec1172a4c3384b8b800b3a8896cc2c1b20e

https://git.kernel.org/stable/c/6112fba4150039ccd90e29f2d1b788c73ad7b3dd

https://git.kernel.org/stable/c/90f0109019e6817eb40a486671b7722d1544ae29

https://git.kernel.org/stable/c/96612bf2712cd961dbd9b52f3a9b4ab668f57628

https://git.kernel.org/stable/c/e244cd8b51001ba480f274c44dba9002813a4739

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