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CVE PROGRAM SOURCE RECORD9.1 Critical

CVE-2026-93228

svcrdma: Reject Write/Reply chunks with segcount 0

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Status
Published
Published
Updated
Assigning organization
Linux

Description

In the Linux kernel, the following vulnerability has been resolved: svcrdma: Reject Write/Reply chunks with segcount 0 A peer can send a Write or Reply chunk whose segcount field is zero. xdr_check_write_chunk() only rejects segcount > rc_maxpages, so zero passes the range check, and xdr_inline_decode(stream, 0) returns the current (non-NULL) cursor without advancing. The function returns true and pcl_alloc_write() then links a struct svc_rdma_chunk with ch_segcount == 0 onto rc_write_pcl or rc_reply_pcl. An earlier patch in this series made pcl_for_each_segment() safe for ch_segcount == 0, so this no longer drives the memory walk it used to. Rejecting the malformed frame at the decode boundary is still worthwhile as defense in depth: it keeps degenerate zero-segment chunks off the parsed chunk lists entirely, so any future consumer that walks ch_segments directly cannot observe one, and it makes the zero-floor easy to backport to trees where the macro change is more intrusive. RFC 8166 has no meaning for a Write/Reply chunk that describes no remote buffer, so no legitimate client is affected. xdr_check_reply_chunk() funnels Reply chunks through xdr_check_write_chunk() and inherits the same rejection. pcl_alloc_write() also links each chunk onto the parsed chunk list before filling its segment array. If a future change weakens the segcount-0 rejection, an incomplete chunk is visible to consumers during the fill loop. Reorder so that list_add_tail() follows the segment fill loop, ensuring only fully-populated chunks appear on the list.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 to < ac730b8cbaeec6831116e1455d909ecbdcdcbd34affected
  • 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 to < 28c5a3a572f6cf81ac304459cfd515480995d62aaffected
  • 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 to < fe533ae1bed2ef2b3d54ee7ab410da1874ed3d4faffected
  • 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 to < a798714b58041e88716db3bf8fb03ae13eecd54aaffected
  • 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 to < 45dbdb2637b7fc5f1355b588780d2a7fb0516805affected
  • 78147ca8b4a9b6cf0e597ddd6bf17959e08376c2 to < 9808eb7656666acc7291bae9ab6b987bd16e47e0affected

Linux Linux

Default version status: affected

  • 5.11affected
  • 0 to < 5.11unaffected
  • 6.1.191 to ≤ 6.1.*unaffected
  • 6.6.160 to ≤ 6.6.*unaffected
  • 6.12.111 to ≤ 6.12.*unaffected
  • 6.18.50 to ≤ 6.18.*unaffected
  • 7.2.4 to ≤ 7.2.*unaffected
  • 7.3 to ≤ *unaffected

References