CVE-2026-89533

Description

In the Linux kernel, the following vulnerability has been resolved: svcrdma: Fix offset arithmetic in read_chunk_range svc_rdma_read_chunk_range() walks a Read chunk's segment list to build a sub-range starting at byte offset and spanning length bytes for a Position-Zero or Call chunk. Two arithmetic defects in the per-segment loop produce wrong DMA lengths and a u32 underflow: pcl_for_each_segment(segment, chunk) { if (offset > segment->rs_length) { offset -= segment->rs_length; continue; } dummy.rs_handle = segment->rs_handle; dummy.rs_length = min_t(u32, length, segment->rs_length) - offset; dummy.rs_offset = segment->rs_offset + offset; First, the skip predicate uses '>' instead of '>='. When offset equals the segment's full rs_length, the segment is fully consumed and should be skipped, but the loop falls through into the body. The resulting dummy.rs_length is min_t(u32, length, rs_length) - rs_length, which underflows to a near-UINT_MAX u32 when length is smaller than rs_length, or is zero otherwise. Second, the length formula subtracts offset from the min_t() result rather than from segment->rs_length before the cap. For offset > 0 the segment's residual is rs_length - offset, not rs_length, so the cap must be applied to the residual. With the current bracketing, whenever length is smaller than rs_length - offset the per-segment length becomes length - offset instead of length, silently dropping offset bytes from the rebuilt chunk. Combined with the boundary case above it also enables the u32 underflow path, which propagates a huge nr_bvec into svc_rdma_build_read_segment() and a multi-MiB kmalloc_array_node() in svc_rdma_get_rw_ctxt(). Additionally, svc_rdma_read_call_chunk() can invoke this function with length == 0 when the last Read chunk ends exactly at the end of the Call chunk. With the corrected >= predicate, every segment is skipped and the function returns the initial -EINVAL, rejecting a valid request. Return success immediately when length is zero. Also break out of the loop once length is fully consumed to avoid passing zero-length segments to svc_rdma_build_read_segment(). Fix by using '>=' so a fully-consumed segment is skipped, by moving '- offset' inside min_t() so the cap is applied to the segment's residual length, by returning success for zero-length requests, and by stopping iteration when the requested range has been consumed.

Gravité et risque d'exploitation

CVE-2026-89533 obtient un score CVSS de 9.8/10, soit une gravité critique. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.50 %, ce qui la place devant 41.7 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <5.11, <=6.1.*, <=6.12.*, 5.15.221, <4a44c140cc2f3643a39e258bb0c0ab9d0f494f5e, d7cc73972661be4a02a1b09f1d9b3283c6c05154, 0, <cba8543c18cf42fd80fd63effb6df6ff4f7e73ce, <10873311f91db9454e2fadbf9866bc819e0646d9, 7.2.4, 5.11, 6.1.188, <=6.6.*, 6.6.157, <addbf02dfe3b25e7e38e03bbd4e2a6ed86a14be7, <=6.18.*, <=7.2.*, <6ee4dc7476b3abc92ec1d444533a559f33f59561, <4493c96bbd0068fadf69cbae8d13426202e34cdc, <a46b35f213c2426f5d6a0458a8f7e873fc59cdfd, <=*, <=5.15.*, 6.18.50, 6.12.109, 7.3) est présent sur votre parc.
• Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
• À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
• Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.

Références

• https://git.kernel.org/stable/c/10873311f91db9454e2fadbf9866bc819e0646d9
• https://git.kernel.org/stable/c/addbf02dfe3b25e7e38e03bbd4e2a6ed86a14be7
• https://git.kernel.org/stable/c/cba8543c18cf42fd80fd63effb6df6ff4f7e73ce
• https://git.kernel.org/stable/c/6ee4dc7476b3abc92ec1d444533a559f33f59561
• https://git.kernel.org/stable/c/a46b35f213c2426f5d6a0458a8f7e873fc59cdfd
• https://git.kernel.org/stable/c/4493c96bbd0068fadf69cbae8d13426202e34cdc
• https://git.kernel.org/stable/c/4a44c140cc2f3643a39e258bb0c0ab9d0f494f5e