SUNRPC: fix gssx_dec_option_array error path bugs

Summary

In the Linux kernel, the following vulnerability has been resolved: SUNRPC: fix gssx_dec_option_array error path bugs Four coupled defects in the gssx XDR option-array decoder make the error paths unsafe: a NULL deref in the caller, a refcount leak on the decoded group_info, and a latent use-after-free that the leak fix would otherwise expose. gssx_dec_option_array() sets oa->count = 1 before allocating oa->data. If that allocation fails, -ENOMEM is returned with oa->count == 1 and oa->data == NULL. All other error paths jump to free_oa: which frees oa->data and NULLs it but also leaves oa->count == 1. The caller trusts the count: gssp_accept_sec_context_upcall() gssx_dec_accept_sec_context() gssx_dec_option_array() /* fails, count=1 data=NULL */ data = res.options.data[0].value /* NULL deref */ Independently, free_creds: releases the partially decoded svc_cred with a bare kfree(creds). gssx_dec_linux_creds() installs a groups_alloc() result into creds->cr_group_info; that object is kvmalloc-backed and refcounted, and only put_group_info() reaches kvfree(). A plain kfree(creds) drops the wrapper and leaks the group_info allocation. The natural fix for the leak is to call free_svc_cred(creds) before kfree(creds), but free_svc_cred() invokes put_group_info() on creds->cr_group_info unconditionally when non-NULL. The existing out_free_groups: path in gssx_dec_linux_creds() already called groups_free() on that pointer without clearing it, so once free_svc_cred() is wired in, the subsequent put_group_info() would touch freed memory. Fix all four together: • Move the oa->count = 1 assignment below the oa->data allocation so it is never set when oa->data is NULL. • Reset oa->count to 0 at free_oa: so count and data stay coherent and the caller sees an empty option array. • Call free_svc_cred(creds) before kfree(creds) at free_creds: so the refcounted cr_group_info is released. free_svc_cred() either NULL-guards each field explicitly (cr_group_info has an if() check) or delegates to a helper that is NULL-safe itself (kfree for the string fields, gss_mech_put() which guards with if(gm) at gss_mech_switch.c:342), so it is safe to call on a partially decoded svc_cred where only cr_uid/cr_gid/cr_group_info have been written and everything else is zero from kzalloc. • In gssx_dec_linux_creds()'s out_free_groups: path, release cr_group_info with put_group_info() rather than groups_free() so the teardown matches free_svc_cred()'s refcount-aware path, and clear the pointer so a later free_svc_cred() on the same creds does not release it a second time.

Timeline

1. Sep 11, 2026, 7:44 PM UTCCVE published
2. Oct 16, 2026, 7:23 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: yes · Technical impact: partial

3. Oct 30, 2026, 12:32 PM UTCRecord last updated

Affected versions

• Linux Linux

  From 5.10.214 · fixed in 5.10.273; From 5.15.153 · fixed in 5.15.224; From 6.1.83 · fixed in 6.1.191; From 6.6.23 · fixed in 6.6.160; From 4.19.311 · fixed in 4.20; From 5.4.273 · fixed in 5.5; From 6.7.11 · fixed in 6.8; From 6.8.2 · fixed in 6.9

• Linux Linux

  6.9

• KernelLinux

  fixed in 6.6.160; From 6.7.0 · fixed in 6.12.111; From 6.9.0 · fixed in 6.18.51; From 6.13.0 · fixed in 7.2.4

References 8