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s390/pci: Fix use-after-free race in zpci floating interrupt cleanup From: Niklas Schnelle To: Tobias Schumacher , Gerd Bayer , Julian Ruess , Farhan Ali , Christian Borntraeger , Halil Pasic , Matthew Rosato Cc: Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Sven Schnelle , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20261005-s390_irq_domain_fixes-v2-4-d45b824874c0@linux.ibm.com> References: <20261005-s390_irq_domain_fixes-v2-0-d45b824874c0@linux.ibm.com> <20261005-s390_irq_domain_fixes-v2-4-d45b824874c0@linux.ibm.com> Autocrypt: addr=schnelle@linux.ibm.com; prefer-encrypt=mutual; keydata=mQINBGHm3M8BEAC+MIQkfoPIAKdjjk84OSQ8erd2OICj98+GdhMQpIjHXn/RJdCZLa58k /ay5x0xIHkWzx1JJOm4Lki7WEzRbYDexQEJP0xUia0U+4Yg7PJL4Dg/W4Ho28dRBROoJjgJSLSHwc 3/1pjpNlSaX/qg3ZM8+/EiSGc7uEPklLYu3gRGxcWV/944HdUyLcnjrZwCn2+gg9ncVJjsimS0ro/ 2wU2RPE4ju6NMBn5Go26sAj1owdYQQv9t0d71CmZS9Bh+2+cLjC7HvyTHKFxVGOznUL+j1a45VrVS 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malwarescore=0 clxscore=1015 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2610060076 On Mon, 2026-10-05 at 14:03 +0200, Tobias Schumacher wrote: > zpci_clear_irq() stops the adapter from raising new interrupts for the > function, but a zpci_floating_irq_handler() already running on another CP= U > can still be scanning zdev->aibv when zpci_msi_teardown_floating() releas= es > it. >=20 > Clear the zpci_ibv[] entry so no further handler picks the vector up, the= n > wait for a grace period before releasing it. The handler runs inside the > rcu_read_lock() section that do_airq_interrupt() holds across > airq->handler(), so synchronize_rcu() drains any handler still in flight. > Free the summary bit only after the grace period, so it cannot be handed = to > another device while a reader still holds the old pointer. >=20 > zpci_ibv served both delivery modes, indexed by summary bit under > FLOATING and by cpu under DIRECTED. Only the floating vectors are > published to and torn down under the interrupt handler, so split the > directed vectors out into zpci_dibv and annotate zpci_ibv __rcu, which > lets sparse check the accessors above. >=20 > Fixes: f770950a4709 ("s390/pci: Migrate s390 IRQ logic to IRQ domain API"= ) > Cc: stable@vger.kernel.org > Signed-off-by: Tobias Schumacher > --- > arch/s390/pci/pci_irq.c | 60 +++++++++++++++++++++++++++----------------= ------ > 1 file changed, 33 insertions(+), 27 deletions(-) >=20 --- snip --- > @@ -660,10 +664,12 @@ void __init zpci_irq_exit(void) > =20 > if (irq_delivery =3D=3D DIRECTED) { > for_each_possible_cpu(cpu) { > - airq_iv_release(zpci_ibv[cpu]); > + airq_iv_release(zpci_dibv[cpu]); > } > + kfree(zpci_dibv); > + } else { > + kfree(zpci_ibv); > } > - kfree(zpci_ibv); > if (zpci_sbv) > airq_iv_release(zpci_sbv); > unregister_adapter_interrupt(&zpci_airq); This is pre-existing but my additional LLM review noticed it. It seems like a theoretical race and against the reverse cleanup vs setup rule, that kfree(zpci_ibv) is done before unregister_adapter_interrupt().=20 Thanks, Niklas