svcrdma: Fix pcl_for_each_segment for empty chunks

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Summary

CVECVE-2026-89532
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-11 20:19:36 UTC
Updated2026-09-11 20:19:36 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: svcrdma: Fix pcl_for_each_segment for empty chunks When a parsed chunk list contains a chunk whose ch_segcount is zero, pcl_for_each_segment computes its inclusive upper bound as &chunk->ch_segments[ch_segcount - 1]. ch_segcount is u32, so the subtraction wraps to 0xFFFFFFFF and the bound lands far past the ch_segments flex array. The loop body then walks unrelated memory at sizeof(struct svc_rdma_segment) stride until it faults. A zero-segcount chunk is reachable from the wire: xdr_check_write_chunk() only rejects segcount values greater than rc_maxpages, and pcl_alloc_write() links a freshly allocated chunk onto rc_write_pcl/rc_reply_pcl before its segment-fill loop runs, so a Write or Reply chunk advertising zero segments leaves ch_segcount == 0 on the list. When the transport has negotiated Send-With-Invalidate, svc_rdma_get_inv_rkey() iterates all four PCLs with pcl_for_each_segment and dereferences segment->rs_handle on each iteration, turning the underflow into an out-of-bounds read and a general protection fault. xdr_check_write_list / xdr_check_reply_chunk pcl_alloc_write() chunk = pcl_alloc_chunk(...) /* ch_segcount = 0 */ list_add_tail(&chunk->ch_list, &pcl->cl_chunks) /* fill loop iterates zero times for wire segcount 0 */ svc_rdma_get_inv_rkey() pcl_for_each_chunk(rc_write_pcl) pcl_for_each_segment(segment, chunk) pos <= &ch_segments[0u - 1u] /* 0xFFFFFFFF */ segment->rs_handle /* OOB read -> GPF */ Fix by switching the macro to a half-open upper bound that uses ch_segcount directly. For ch_segcount == 0 the loop start equals the loop end and the body is skipped; for ch_segcount > 0 the iteration range is unchanged. All six existing call sites in net/sunrpc/xprtrdma/svc_rdma_recvfrom.c and net/sunrpc/xprtrdma/svc_rdma_rw.c remain correct under the new bound, so no caller changes are needed.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 9c5a03c3dc505c0295339b0a1b9e4fe36447e482 git Not specified
CNA Linux Linux affected 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 a1c954ca4977a4e6ec73ef92fe48073ec54f9fc8 git Not specified
CNA Linux Linux affected 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 6d33a7e6bf6c6b293a266a617201285a1ad32c56 git Not specified
CNA Linux Linux affected 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 b7713a784c59515d0aba558c8f5df6a0164dd3a9 git Not specified
CNA Linux Linux affected 5.11 Not specified
CNA Linux Linux unaffected 5.11 semver Not specified
CNA Linux Linux unaffected 6.12.109 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.50 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.4 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/9c5a03c3dc505c0295339b0a1b9e4fe36447e482 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/b7713a784c59515d0aba558c8f5df6a0164dd3a9 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a1c954ca4977a4e6ec73ef92fe48073ec54f9fc8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/6d33a7e6bf6c6b293a266a617201285a1ad32c56 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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