Bug 2383910 (CVE-2025-38481)

Summary: CVE-2025-38481 kernel: comedi: Fail COMEDI_INSNLIST ioctl if n_insns is too large
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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Description OSIDB Bzimport 2025-07-28 12:02:45 UTC 
In the Linux kernel, the following vulnerability has been resolved:

comedi: Fail COMEDI_INSNLIST ioctl if n_insns is too large

The handling of the `COMEDI_INSNLIST` ioctl allocates a kernel buffer to
hold the array of `struct comedi_insn`, getting the length from the
`n_insns` member of the `struct comedi_insnlist` supplied by the user.
The allocation will fail with a WARNING and a stack dump if it is too
large.

Avoid that by failing with an `-EINVAL` error if the supplied `n_insns`
value is unreasonable.

Define the limit on the `n_insns` value in the `MAX_INSNS` macro.  Set
this to the same value as `MAX_SAMPLES` (65536), which is the maximum
allowed sum of the values of the member `n` in the array of `struct
comedi_insn`, and sensible comedi instructions will have an `n` of at
least 1.
Comment 1 Avinash Hanwate 2025-07-28 17:51:32 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025072814-CVE-2025-38481-1476@gregkh/T