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.
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS Score: 9.8
AV:N - svcrdma is nfsd's RPC-over-RDMA transport; a remote peer reaches Read-chunk reconstruction on an enabled NFS/RDMA listener over routable iWARP or RoCE, consistent with prior kernel CNA scores for this subsystem.
AC:L - The attacker fully controls the wire-supplied Read-chunk position (only 4-byte alignment is checked) and can deterministically underflow gap/tail lengths or copy past the receive buffer, with no race or uncontrollable layout required.
PR:N - svc_rdma_process_read_list() and svc_rdma_read_complete_one() run in svc_rdma_recvfrom() while assembling the transport message, before svc_process() performs RPC or NFS authentication, and RDMA CM accept has no credential check.
UI:N - Sending a crafted RPC-over-RDMA message with a malicious Read list is sufficient; no victim mount, click, or other user action is required.
S:U - The vulnerable NFS/RDMA service and the affected kernel memory belong to the same host kernel security authority; this is not a VM, IOMMU, or sandbox escape.
C:H - A position past the inline body underflows the tail kvec so the XDR decoder reads adjacent slab, and overlapping chunks make svc_rdma_copy_inline_range() memcpy past the receive buffer into request pages returned on the Reply channel, disclosing kernel memory.
I:H - The reconstructed xdr_buf uses attacker-controlled head/tail lengths pointing into adjacent slab; XDR shift/copy helpers then memcpy through those kvecs, producing an out-of-bounds kernel write that can corrupt adjacent objects and hijack control flow.
A:H - The unbounded inline copy and inflated kvec lengths walk unmapped memory or trip decoder/WARN paths, causing a kernel oops or panic that an unauthenticated peer can trigger repeatedly.
| Attack Vector |
Network |
Scope |
Unchanged |
| Attack Complexity |
Low |
Confidentiality Impact |
High |
| Privileges Required |
None |
Integrity Impact |
High |
| User Interaction |
None |
Availability Impact |
High |
AV:N - svcrdma is nfsd's RPC-over-RDMA transport; a remote peer reaches Read-chunk reconstruction on an enabled NFS/RDMA listener over routable iWARP or RoCE, consistent with prior kernel CNA scores for this subsystem.
AC:L - The attacker fully controls the wire-supplied Read-chunk position (only 4-byte alignment is checked) and can deterministically underflow gap/tail lengths or copy past the receive buffer, with no race or uncontrollable layout required.
PR:N - svc_rdma_process_read_list() and svc_rdma_read_complete_one() run in svc_rdma_recvfrom() while assembling the transport message, before svc_process() performs RPC or NFS authentication, and RDMA CM accept has no credential check.
UI:N - Sending a crafted RPC-over-RDMA message with a malicious Read list is sufficient; no victim mount, click, or other user action is required.
S:U - The vulnerable NFS/RDMA service and the affected kernel memory belong to the same host kernel security authority; this is not a VM, IOMMU, or sandbox escape.
C:H - A position past the inline body underflows the tail kvec so the XDR decoder reads adjacent slab, and overlapping chunks make svc_rdma_copy_inline_range() memcpy past the receive buffer into request pages returned on the Reply channel, disclosing kernel memory.
I:H - The reconstructed xdr_buf uses attacker-controlled head/tail lengths pointing into adjacent slab; XDR shift/copy helpers then memcpy through those kvecs, producing an out-of-bounds kernel write that can corrupt adjacent objects and hijack control flow.
A:H - The unbounded inline copy and inflated kvec lengths walk unmapped memory or trip decoder/WARN paths, causing a kernel oops or panic that an unauthenticated peer can trigger repeatedly.
CVSS 3.1