Bug 2408808 (CVE-2025-40106)

Summary: CVE-2025-40106 kernel: comedi: fix divide-by-zero in comedi_buf_munge()
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 2025-10-31 10:01:37 UTC 
In the Linux kernel, the following vulnerability has been resolved:

comedi: fix divide-by-zero in comedi_buf_munge()

The comedi_buf_munge() function performs a modulo operation
`async->munge_chan %= async->cmd.chanlist_len` without first
checking if chanlist_len is zero. If a user program submits a command with
chanlist_len set to zero, this causes a divide-by-zero error when the device
processes data in the interrupt handler path.

Add a check for zero chanlist_len at the beginning of the
function, similar to the existing checks for !map and
CMDF_RAWDATA flag. When chanlist_len is zero, update
munge_count and return early, indicating the data was
handled without munging.

This prevents potential kernel panics from malformed user commands.
Comment 1 Jon Moroney 2025-10-31 16:26:29 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025103155-CVE-2025-40106-ed47@gregkh/T