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[PATCH v7 0/8] dma-buf: Use revoke mechanism to invalidate shared buffers

by Leon Romanovsky

Changelog: v7: * Fixed messed VFIO patch due to rebase. v6: https://patch.msgid.link/20260130-dmabuf-revoke-v6-0-06278f9b7bf0@nvidia.com * Added Reviewed-by tags. * Changed for blocking wait_for_completion() in VFIO * Fixed race between ->attach and move_notify, where priv->revoked is flipped and lock is released. v5: https://patch.msgid.link/20260124-dmabuf-revoke-v5-0-f98fca917e96@nvidia.com * Documented the DMA-BUF expectations around DMA unmap. * Added wait support in VFIO for DMA unmap. * Reordered patches. * Improved commit messages to document even more. v4: https://lore.kernel.org/all/20260121-dmabuf-revoke-v4-0-d311cbc8633d@nvidia… * Changed DMA_RESV_USAGE_KERNEL to DMA_RESV_USAGE_BOOKKEEP. * Made .invalidate_mapping() truly optional. * Added patch which renames dma_buf_move_notify() to be dma_buf_invalidate_mappings(). * Restored dma_buf_attachment_is_dynamic() function. v3: https://lore.kernel.org/all/20260120-dmabuf-revoke-v3-0-b7e0b07b8214@nvidia… * Used Jason's wordings for commits and cover letter. * Removed IOMMUFD patch. * Renamed dma_buf_attachment_is_revoke() to be dma_buf_attach_revocable(). * Added patch to remove CONFIG_DMABUF_MOVE_NOTIFY. * Added Reviewed-by tags. * Called to dma_resv_wait_timeout() after dma_buf_move_notify() in VFIO. * Added dma_buf_attach_revocable() check to VFIO DMABUF attach function. * Slightly changed commit messages. v2: https://patch.msgid.link/20260118-dmabuf-revoke-v2-0-a03bb27c0875@nvidia.com * Changed series to document the revoke semantics instead of implementing it. v1: https://patch.msgid.link/20260111-dmabuf-revoke-v1-0-fb4bcc8c259b@nvidia.com ------------------------------------------------------------------------- This series is based on latest VFIO fix, which will be sent to Linus very soon. https://lore.kernel.org/all/20260121-vfio-add-pin-v1-1-4e04916b17f1@nvidia.… Thanks ------------------------------------------------------------------------- This series documents a dma-buf “revoke” mechanism: to allow a dma-buf exporter to explicitly invalidate (“kill”) a shared buffer after it has been distributed to importers, so that further CPU and device access is prevented and importers reliably observe failure. The change in this series is to properly document and use existing core “revoked” state on the dma-buf object and a corresponding exporter-triggered revoke operation. dma-buf has quietly allowed calling move_notify on pinned dma-bufs, even though legacy importers using dma_buf_attach() would simply ignore these calls. The intention was that move_notify() would tell the importer to expedite it's unmapping process and once the importer is fully finished with DMA it would unmap the dma-buf which finally signals that the importer is no longer ever going to touch the memory again. Importers that touch past their unmap() call can trigger IOMMU errors, AER and beyond, however read-and-discard access between move_notify() and unmap is allowed. Thus, we can define the exporter's revoke sequence for pinned dma-buf as: dma_resv_lock(dmabuf->resv, NULL); // Prevent new mappings from being established priv->revoked = true; // Tell all importers to eventually unmap dma_buf_invalidate_mappings(dmabuf); // Wait for any inprogress fences on the old mapping dma_resv_wait_timeout(dmabuf->resv, DMA_RESV_USAGE_BOOKKEEP, false, MAX_SCHEDULE_TIMEOUT); dma_resv_unlock(dmabuf->resv, NULL); // Wait for all importers to complete unmap wait_for_completion(&priv->unmapp_comp); However, dma-buf also supports importers that don't do anything on move_notify(), and will not unmap the buffer in bounded time. Since such importers would cause the above sequence to hang, a new mechanism is needed to detect incompatible importers. Introduce dma_buf_attach_revocable() which if true indicates the above sequence is safe to use and will complete in kernel-only bounded time for this attachment. Unfortunately dma_buf_attach_revocable() is going to fail for the popular RDMA pinned importer, which means we cannot introduce it to existing places using pinned move_notify() without potentially breaking existing userspace flows. Existing exporters that only trigger this flow for RAS errors should not call dma_buf_attach_revocable() and will suffer an unbounded block on the final completion, hoping that the userspace will notice the RAS and clean things up. Without revoke support on the RDMA pinned importers it doesn't seem like any other non-breaking option is currently possible. For new exporters, like VFIO and RDMA, that have userspace triggered revoke events, the unbouned sleep would not be acceptable. They can call dma_buf_attach_revocable() and will not work with the RDMA pinned importer from day 0, preventing regressions. In the process add documentation explaining the above details. Thanks Signed-off-by: Leon Romanovsky <leonro(a)nvidia.com> --- Leon Romanovsky (8): dma-buf: Rename .move_notify() callback to a clearer identifier dma-buf: Rename dma_buf_move_notify() to dma_buf_invalidate_mappings() dma-buf: Always build with DMABUF_MOVE_NOTIFY vfio: Wait for dma-buf invalidation to complete dma-buf: Make .invalidate_mapping() truly optional dma-buf: Add dma_buf_attach_revocable() vfio: Permit VFIO to work with pinned importers iommufd: Add dma_buf_pin() drivers/dma-buf/Kconfig | 12 ----- drivers/dma-buf/dma-buf.c | 69 ++++++++++++++++++++----- drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 14 ++--- drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 2 +- drivers/gpu/drm/amd/amdkfd/Kconfig | 2 +- drivers/gpu/drm/virtio/virtgpu_prime.c | 2 +- drivers/gpu/drm/xe/tests/xe_dma_buf.c | 7 ++- drivers/gpu/drm/xe/xe_bo.c | 2 +- drivers/gpu/drm/xe/xe_dma_buf.c | 14 ++--- drivers/infiniband/core/umem_dmabuf.c | 13 ----- drivers/infiniband/hw/mlx5/mr.c | 2 +- drivers/iommu/iommufd/pages.c | 11 +++- drivers/iommu/iommufd/selftest.c | 2 +- drivers/vfio/pci/vfio_pci_dmabuf.c | 80 ++++++++++++++++++++++------- include/linux/dma-buf.h | 17 +++--- 15 files changed, 153 insertions(+), 96 deletions(-) --- base-commit: 61ceaf236115f20f4fdd7cf60f883ada1063349a change-id: 20251221-dmabuf-revoke-b90ef16e4236 Best regards, -- Leon Romanovsky <leonro(a)nvidia.com>

2 weeks, 6 days

Cryptera Chain Signals Summary – Focus On Transparency During Recovery Process

by Yulie Morgan

After experiencing a bridge exploit I worked with Cryptera Chain Signals to understand the movement of funds. Their process was transparent from day one: secure intake, detailed mapping with multi-layer attribution, and regular updates with visual explanations. They showed how cross-chain hops complicated the trail and why some paths reach natural limits. The educational discussions helped me grasp broader concepts — immutable records, pattern detection, and behavioral analysis. Rather than technical overload, the explanations focused on what each step revealed about the incident. Recovery options were limited by timing, but the clarity removed guesswork. I particularly appreciated the practical security advice that followed: hardware wallet recommendations, seed phrase protection, and checks for anomalous activity. These became part of my routine. The engagement was professional, informative, and free of pressure. It provided both a factual account of the loss and lasting insights into safer crypto practices. Cryptera Chain Signals Website: https://www.crypterachainsignals.com Email: info(a)crypterachainsignals.com

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Cryptera Chain Signals Experience – Realistic Forensics And Prevention Advice

by Yulie Morgan

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Detailed Feedback On Cryptera Chain Signals Support And Educational Value

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Cryptera Chain Signals Review – Insights Gained From Forensics Engagement

by Yulie Morgan

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Cryptera Chain Signals User Account – Tracing Process And Key Learnings

by Yulie Morgan

After a phishing incident in late February 2026 I spent time researching options before contacting Cryptera Chain Signals. The intake process was straightforward — they asked for transaction hashes, wallet addresses, and a short timeline, nothing more sensitive. Within a few days they sent an initial graph showing how the funds had moved from my wallet through a bridge and into a mixer service. The multi-layer attribution explanation was particularly helpful. They walked me through how clustering works, why certain addresses grouped together, and how behavioral patterns (like repeated small transfers) can reveal control even after obfuscation. It was the first time I really understood how blockchain transparency operates in practice. Recovery was limited because the assets had already been dispersed, but the detailed report clarified every step and helped me close the chapter without lingering questions. What stayed with me was the education component. We discussed common phishing tactics, how fake interfaces mimic legitimate ones, and simple habits like bookmarking official sites and using hardware wallets. I also learned about monitoring tools that flag unusual activity before it escalates. The team answered questions patiently without any pressure. Overall it was a clear, educational process that turned a frustrating experience into practical knowledge I now apply daily. Cryptera Chain Signals Website: https://www.crypterachainsignals.com Email: info(a)crypterachainsignals.com

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Cryptera Chain Signals Provides Overview Of Forensics Tools Used In Digital Asset Cases

by Yulie Morgan

Cryptera Chain Signals has outlined the types of specialized tools and methods employed in digital asset investigations. Operating for 28 years with over 426 completed projects and a 4.28 out of 5 rating from 2,467 client reviews, the firm relies on a combination of public blockchain data and proprietary multi-layer attribution techniques. Core tools include transaction graph visualization software that plots every transfer as interconnected nodes, making complex flows visible at a glance. Address clustering algorithms then group seemingly unrelated wallets that share behavioral traits such as similar transaction sizes or timing. These layers allow Cryptera Chain Signals to trace assets even after they pass through obfuscation services. Clients receive explanations of these tools in plain language. For instance, they learn how public ledgers function like an open database where every entry is permanent, yet interpreting that data requires experience in pattern recognition. The firm also discusses limitations — certain privacy-focused protocols or rapid cross-chain movements can reduce visibility, and no tool can access private keys or off-chain information. Education extends to everyday applications. Cryptera Chain Signals shows clients how to use free explorers for basic checks, why verifying contract addresses matters, and how to spot anomalies like sudden large withdrawals. Sessions cover wallet best practices and response protocols for suspected incidents. All work follows strict privacy protocols, beginning with minimal data collection and progressing only with client consent. Reports are designed to educate rather than overwhelm, helping users understand both the incident and broader blockchain principles. Cryptera Chain Signals Website: https://www.crypterachainsignals.com Email: info(a)crypterachainsignals.com

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Cryptera Chain Signals Discusses The Importance Of Prompt Action In Blockchain Analysis

by Yulie Morgan

Cryptera Chain Signals continues to stress the value of timely engagement when cryptocurrency assets go missing. With 28 years of experience and more than 426 projects documented at a 4.28 out of 5 average client rating from 2,467 reviews, the firm sees clear patterns in cases where early analysis made a measurable difference. Blockchain data is permanent, but the ability to act on that data diminishes rapidly. Once funds move through additional layers — bridges, decentralized exchanges, or mixing services — the transaction graph becomes more complex. Cryptera Chain Signals multi-layer attribution process begins immediately upon receiving hashes and addresses, constructing visual maps that reveal clusters and potential endpoints. This rapid mapping can identify regulated platforms where intervention remains possible. The company educates clients on why speed matters. Many loss scenarios involve automated scripts that disperse assets within hours. Understanding basic mechanics, such as how gas fees can indicate rushed transfers or how address clustering reveals control, helps users appreciate the window of opportunity. Cryptera Chain Signals also explains common self-tracing mistakes that can inadvertently alert bad actors or scatter funds further. Educational components include guidance on immediate documentation (saving every communication and transaction detail) and basic security hygiene (hardware wallets, offline storage, verified connections). Clients learn to differentiate between recoverable situations and those limited by design, gaining clarity on realistic expectations without false optimism. The firm’s structured process — intake, analysis, reporting, and updates — keeps clients informed at every stage. This transparency helps individuals learn from the incident while understanding the broader blockchain environment. Cryptera Chain Signals Website: https://www.crypterachainsignals.com Email: info(a)crypterachainsignals.com

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Cryptera Chain Signals Highlights Educational Initiatives For Scam Awareness In 2026

by Yulie Morgan

As reports of cryptocurrency-related incidents continue in 2026, Cryptera Chain Signals has expanded its focus on educational resources to help users better understand scam mechanics and protective measures. The firm, active since 1998 with more than 426 projects completed and a 4.28 out of 5 client rating from 2,467 reviews, integrates learning into every stage of its work. Common vectors discussed include phishing campaigns that use fake wallet interfaces or social media impersonation to capture credentials. Cryptera Chain Signals explains how these attacks often begin with seemingly legitimate messages and escalate to requests for seed phrases or private keys. Another area of emphasis is investment schemes where platforms promise high returns but lack proper smart contract audits or liquidity locks. The company teaches clients to check for red flags such as anonymous development teams, sudden changes in trading volume, or developers moving large portions of raised funds. Through multi-layer attribution, Cryptera Chain Signals shows clients how funds typically move after a successful scam — often toward mixers or offshore exchanges. Visual transaction graphs make these paths easier to follow, turning technical data into understandable narratives. Clients learn why acting within the first 48 hours can preserve more options, as funds become harder to locate once laundered. Preventive education covers wallet security fundamentals: keeping seed phrases offline, using hardware devices, enabling multi-factor authentication, and avoiding connections to unverified sites. The firm also discusses emerging risks such as deepfake videos used for impersonation and cross-chain bridge exploits, providing context on how these attacks function and how basic monitoring can help detect them early. Cryptera Chain Signals delivers this information through clear consultations and follow-up materials rather than overwhelming jargon. The goal is to equip individuals with knowledge that extends far beyond any single incident. Cryptera Chain Signals Website: https://www.crypterachainsignals.com Email: info(a)crypterachainsignals.com

3 weeks

Cryptera Chain Signals Examines The Role Of Wallet Attribution In Modern Crypto Investigations

by Yulie Morgan

With cryptocurrency transactions becoming increasingly layered across multiple networks, Cryptera Chain Signals has released observations on the growing importance of advanced wallet attribution techniques in digital asset investigations. The firm, which began operations in 1998 and has completed more than 426 documented projects, maintains an average client rating of 4.28 out of 5 based on 2,467 verified reviews across independent platforms. Wallet attribution involves mapping relationships between addresses by analyzing transaction graphs, clustering patterns, and behavioral signals. Cryptera Chain Signals uses a multi-layer approach that examines not only direct transfers but also indirect connections through mixers, bridges, and chain hops. This method helps reconstruct fund movements in a way that standard blockchain explorers cannot achieve alone. For example, when funds move from Ethereum to a layer-two solution and then through a privacy protocol, attribution tools can still identify clusters controlled by the same entity based on timing, amounts, and reuse patterns. The company notes that this type of analysis is most effective when initiated quickly. Once funds reach unregulated endpoints or undergo extensive mixing, visibility decreases significantly. Cryptera Chain Signals always begins with a secure consultation that collects only transaction hashes, wallet addresses, and timelines — never private keys. From there, forensic teams build visual graphs that illustrate the flow, allowing clients to see exactly where assets traveled and why certain paths become harder to follow. Education forms a central part of every engagement. Clients learn fundamental blockchain concepts such as how public ledgers record every movement immutably, why address reuse can create traceable links, and how gas fee anomalies sometimes signal malicious activity. Sessions also cover practical steps for everyday users: using hardware wallets to keep seed phrases offline, verifying contract addresses before interaction, and monitoring for unusual activity through free on-chain tools. These lessons aim to reduce the likelihood of future incidents by building foundational awareness. Cryptera Chain Signals continues to observe that while attribution can clarify what happened, actual recovery depends on many variables including exchange cooperation and legal frameworks. The firm provides detailed reports that clients can use for their own records or to engage authorities when appropriate. This measured, educational approach has helped maintain consistent client feedback in a rapidly changing environment. Cryptera Chain Signals Website: https://www.crypterachainsignals.com Email: info(a)crypterachainsignals.com

3 weeks

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