The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y git checkout FETCH_HEAD git cherry-pick -x 229e6ee43d2a160a1592b83aad620d6027084aad # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024120651-ruse-sturdily-f7c5@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 229e6ee43d2a160a1592b83aad620d6027084aad Mon Sep 17 00:00:00 2001 From: Pratyush Brahma quic_pbrahma@quicinc.com Date: Fri, 4 Oct 2024 14:34:28 +0530 Subject: [PATCH] iommu/arm-smmu: Defer probe of clients after smmu device bound

Null pointer dereference occurs due to a race between smmu driver probe and client driver probe, when of_dma_configure() for client is called after the iommu_device_register() for smmu driver probe has executed but before the driver_bound() for smmu driver has been called.

Following is how the race occurs:

T1:Smmu device probe T2: Client device probe

really_probe() arm_smmu_device_probe() iommu_device_register() really_probe() platform_dma_configure() of_dma_configure() of_dma_configure_id() of_iommu_configure() iommu_probe_device() iommu_init_device() arm_smmu_probe_device() arm_smmu_get_by_fwnode() driver_find_device_by_fwnode() driver_find_device() next_device() klist_next() /* null ptr assigned to smmu */ /* null ptr dereference while smmu->streamid_mask */ driver_bound() klist_add_tail()

When this null smmu pointer is dereferenced later in arm_smmu_probe_device, the device crashes.

Fix this by deferring the probe of the client device until the smmu device has bound to the arm smmu driver.

Fixes: 021bb8420d44 ("iommu/arm-smmu: Wire up generic configuration support") Cc: stable@vger.kernel.org Co-developed-by: Prakash Gupta quic_guptap@quicinc.com Signed-off-by: Prakash Gupta quic_guptap@quicinc.com Signed-off-by: Pratyush Brahma quic_pbrahma@quicinc.com Link: https://lore.kernel.org/r/20241004090428.2035-1-quic_pbrahma@quicinc.com [will: Add comment] Signed-off-by: Will Deacon will@kernel.org

diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c index 8321962b3714..14618772a3d6 100644 --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c @@ -1437,6 +1437,17 @@ static struct iommu_device *arm_smmu_probe_device(struct device *dev) goto out_free; } else { smmu = arm_smmu_get_by_fwnode(fwspec->iommu_fwnode); + + /* + * Defer probe if the relevant SMMU instance hasn't finished + * probing yet. This is a fragile hack and we'd ideally + * avoid this race in the core code. Until that's ironed + * out, however, this is the most pragmatic option on the + * table. + */ + if (!smmu) + return ERR_PTR(dev_err_probe(dev, -EPROBE_DEFER, + "smmu dev has not bound yet\n")); }

ret = -EINVAL;