Bug 2406781 (CVE-2025-40046)

Summary: CVE-2025-40046 kernel: io_uring/zcrx: fix overshooting recv limit
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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OS: Linux   
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Description OSIDB Bzimport 2025-10-28 12:05:13 UTC 
In the Linux kernel, the following vulnerability has been resolved:

io_uring/zcrx: fix overshooting recv limit

It's reported that sometimes a zcrx request can receive more than was
requested. It's caused by io_zcrx_recv_skb() adjusting desc->count for
all received buffers including frag lists, but then doing recursive
calls to process frag list skbs, which leads to desc->count double
accounting and underflow.
Comment 1 Jon Moroney 2025-10-28 20:20:31 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025102813-CVE-2025-40046-391f@gregkh/T