CVE-2026-89533
svcrdma: Fix offset arithmetic in read_chunk_range
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.
INFO
Published Date :
Sept. 11, 2026, 8:19 p.m.
Last Modified :
Sept. 14, 2026, 1:19 p.m.
Remotely Exploit :
Yes !
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | CRITICAL | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 |
Solution
- Use '>=' to skip fully consumed segments.
- Apply offset subtraction inside min_t().
- Return success for zero-length requests.
- Stop iteration when range is consumed.
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Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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CVE Modified by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Sep. 14, 2026
Action Type Old Value New Value Added Affected Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/89xxx/CVE-2026-89533.json">CVE-2026-89533</a> Added Reference https://git.kernel.org/stable/c/10873311f91db9454e2fadbf9866bc819e0646d9 Added Reference https://git.kernel.org/stable/c/addbf02dfe3b25e7e38e03bbd4e2a6ed86a14be7 Added Reference https://git.kernel.org/stable/c/cba8543c18cf42fd80fd63effb6df6ff4f7e73ce -
CVE Modified by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Sep. 13, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H -
New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Sep. 11, 2026
Action Type Old Value New Value Added 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. Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/89xxx/CVE-2026-89533.json">CVE-2026-89533</a> Added Reference https://git.kernel.org/stable/c/4493c96bbd0068fadf69cbae8d13426202e34cdc Added Reference https://git.kernel.org/stable/c/4a44c140cc2f3643a39e258bb0c0ab9d0f494f5e Added Reference https://git.kernel.org/stable/c/6ee4dc7476b3abc92ec1d444533a559f33f59561 Added Reference https://git.kernel.org/stable/c/a46b35f213c2426f5d6a0458a8f7e873fc59cdfd