CVE-2023-53083: nfsd: don't replace page in rq_pages if it's a continuation of last page

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-05-02 · updated 2026-08-04

Description

In the Linux kernel, the following vulnerability has been resolved: nfsd: don't replace page in rq_pages if it's a continuation of last page The splice read calls nfsd_splice_actor to put the pages containing file data into the svc_rqst->rq_pages array. It's possible however to get a splice result that only has a partial page at the end, if (e.g.) the filesystem hands back a short read that doesn't cover the whole page. nfsd_splice_actor will plop the partial page into its rq_pages array and return. Then later, when nfsd_splice_actor is called again, the remainder of the page may end up being filled out. At this point, nfsd_splice_actor will put the page into the array _again_ corrupting the reply. If this is done enough times, rq_next_page will overrun the array and corrupt the trailing fields -- the rq_respages and rq_next_page pointers themselves. If we've already added the page to the array in the last pass, don't add it to the array a second time when dealing with a splice continuation. This was originally handled properly in nfsd_splice_actor, but commit 91e23b1c3982 ("NFSD: Clean up nfsd_splice_actor()") removed the check for it.

Affected products

Linux kernel: from 5.19 before 6.1.22; from 6.2 before 6.2.9; 6.3-rc1, 6.3-rc2, 6.3-rc3 — fixed in 6.1.22, 6.2.9

How to fix

Upgrade to a fixed version: Linux kernel 6.1.22, 6.2.9. Check the vendor advisory for mitigations.

References

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