svcrdma: Validate Read chunk positions before reconstruction

Overview

In the Linux kernel, the following vulnerability has been resolved:

svcrdma: Validate Read chunk positions before reconstruction

The RPC/RDMA Read chunk position field is supplied by the remote client and stored verbatim in the parsed chunk list. xdr_count_read_segments() checks only 4-byte alignment; it never compares the position against the received inline body length.

In the single-chunk path, svc_rdma_read_complete_one() splits the head and tail kvecs at ch_position. A position past the inline body underflows the tail length, exposing adjacent slab memory to the upper XDR decoder.

In the multi-chunk path, svc_rdma_read_multiple_chunks() computes gap lengths between chunks as unsigned subtractions from ch_position. Overlapping Read chunks cause these subtractions to underflow. A final position past the inline body likewise underflows the trailing gap length. svc_rdma_copy_inline_range() then copies past the receive buffer into request pages that are returned to the client through the Reply channel.

Bound inline-range copies in svc_rdma_copy_inline_range() against the decoded inline RPC body saved in rc_saved_arg. Reject a single Read chunk positioned beyond that body, and reject multi-chunk lists where accumulated read bytes exceed the next chunk's position. Apply the same position and overlap checks in the call-chunk interleaving path.

Affected

• Linux >= d96962e6d0e281bab6a48e83b42f5dce6eb28bf4 < 3861eeabaebe243050952b34063763527c44e1fe
• Linux >= d96962e6d0e281bab6a48e83b42f5dce6eb28bf4 < 5ab3f6d882fe07ae5e61d0bcfeea00b9409155c2
• Linux >= d96962e6d0e281bab6a48e83b42f5dce6eb28bf4 < f84ec84d8d4bc65f9ae23372570349687f66fa39
• Linux >= d96962e6d0e281bab6a48e83b42f5dce6eb28bf4 < 577097455d084610fc31e91e6a61c5793b6f04ba
• Linux >= d96962e6d0e281bab6a48e83b42f5dce6eb28bf4 < 3779b7b9e7d1c8ba4738f9d327de3b0288cefe9b
• Linux 5.11

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

Vendor advisories

• Red Hat VEX · Important · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9 · updated 2026-09-27 · vex