CVE-2026-89996dma-buf: dma-heap: don't publish fd before copy_to_user() succeeds
- —Not scoredno CVSS score yet
- 0.21%Exploitation in 30 daysEPSS · top 88% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
In the Linux kernel, the following vulnerability has been resolved: dma-buf: dma-heap: don't publish fd before copy_to_user() succeeds DMA_HEAP_IOCTL_ALLOC allocates a dma-buf and installs an fd into the caller's fd table via dma_buf_fd() -> fd_install() before dma_heap_ioctl() copies the result back to userspace. If the trailing copy_to_user() fails, userspace never learns the fd number, but the fd (and the underlying dma-buf reference) are already visible to other threads in the same process and are leaked for the lifetime of the process. The obvious "close it on the failure path" fix is unsafe: once fd_install() has run, another thread can already dup() the fd, send it via SCM_RIGHTS, or close() it and let its number be reused, so a subsequent close_fd() from the ioctl path can operate on an unrelated file. This was pointed out by Christian König on v1 [1]. Restructure the allocation path so that fd_install() is the last, unfailable step of a successful ioctl: 1. heap->ops->allocate() creates the dma_buf. 2. get_unused_fd_flags() reserves an fd number in the caller's fd table without publishing it, so no other thread can observe it. 3. copy_to_user() delivers the fd number to userspace; on failure the fd is returned with put_unused_fd() and the dma_buf reference is dropped with dma_buf_put(), leaving no user- visible state behind. 4. dma_buf_fd_install() publishes the fd and emits the trace_dma_buf_fd tracepoint -- from here on the ioctl cannot fail. A new dma_buf_fd_install() helper is introduced in dma-buf.c to wrap fd_install() together with the DMA_BUF_TRACE() call, preserving the export tracing that dma_buf_fd() provides. dma_heap_ioctl_allocate() is refactored to return the struct dma_buf * directly (returning ERR_PTR on failure) so the caller holds the dmabuf reference across steps 3 and 4. The failure at step 3 is easily reachable from userspace: pass a struct dma_heap_allocation_data that lives in a page whose protection is flipped to PROT_READ between copy_from_user() and copy_to_user() (e.g. via mprotect()). Before this change each such ioctl leaks one dmabuf fd; after it, the fd table is unchanged on failure and only /dev/dma_heap/<name> remains open. No UAPI or heap-driver interface change. [1] https://lore.kernel.org/dri-devel/[email protected]/
Timeline
ID reserved
By Linux
- 5 days later
· 5 days later
Published
- 44 days later
· 44 days later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
No CVSS score yet: neither the CNA, CISA nor NVD has scored this CVE. NVD status: Received.
- EPSS (exploitation in 30 days)
- 0.21% · top 88% of all CVEs (12 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: Not scored.
Affected products
- affected c02a81fba74fe3488ad6b08bfb5a1329005418f8 – < 1953ef8d11eb5870fe621259708a90900bead272
- affected c02a81fba74fe3488ad6b08bfb5a1329005418f8 – < ad61defb3e66ac0c598ad6f39b57f15784543d46
- affected c02a81fba74fe3488ad6b08bfb5a1329005418f8 – < 1bf6083a41f810d760c4dcd1b80c5194a92575aa
- affected c02a81fba74fe3488ad6b08bfb5a1329005418f8 – < 69d57dbadb27ffd5eef34fd184bab145500cdabc
- affected c02a81fba74fe3488ad6b08bfb5a1329005418f8 – < 0d4a5d218055db29b50cc07d3d73d27007c2a391
- affected c02a81fba74fe3488ad6b08bfb5a1329005418f8 – < 30d0aff2c65a277135cfd8ea28fa1ee75e0ea4e0
- affected 5.6
- unaffected < 5.6
- unaffected 6.1.191 – ≤ 6.1.*
- unaffected 6.6.160 – ≤ 6.6.*
- unaffected 6.12.112 – ≤ 6.12.*
- unaffected 6.18.52 – ≤ 6.18.*
- unaffected 7.2.5 – ≤ 7.2.*
- unaffected 7.3 – ≤ *
References
References6
- https://git.kernel.org/stable/c/1953ef8d11eb5870fe621259708a90900bead272 (opens in a new tab)
- https://git.kernel.org/stable/c/ad61defb3e66ac0c598ad6f39b57f15784543d46 (opens in a new tab)
- https://git.kernel.org/stable/c/1bf6083a41f810d760c4dcd1b80c5194a92575aa (opens in a new tab)
- https://git.kernel.org/stable/c/69d57dbadb27ffd5eef34fd184bab145500cdabc (opens in a new tab)
- https://git.kernel.org/stable/c/0d4a5d218055db29b50cc07d3d73d27007c2a391 (opens in a new tab)
- https://git.kernel.org/stable/c/30d0aff2c65a277135cfd8ea28fa1ee75e0ea4e0 (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-80604 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-89996)Record last updated .