{"id":"AZL-100656","summary":"CVE-2026-89544 affecting package kernel 6.6.150.1-1","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: fix gssx_dec_option_array error path bugs\n\nFour coupled defects in the gssx XDR option-array decoder make the\nerror paths unsafe: a NULL deref in the caller, a refcount leak on\nthe decoded group_info, and a latent use-after-free that the leak\nfix would otherwise expose.\n\ngssx_dec_option_array() sets oa-\u003ecount = 1 before allocating\noa-\u003edata.  If that allocation fails, -ENOMEM is returned with\noa-\u003ecount == 1 and oa-\u003edata == NULL.  All other error paths jump\nto free_oa: which frees oa-\u003edata and NULLs it but also leaves\noa-\u003ecount == 1.  The caller trusts the count:\n\n    gssp_accept_sec_context_upcall()\n      gssx_dec_accept_sec_context()\n        gssx_dec_option_array()        /* fails, count=1 data=NULL */\n      data = res.options.data[0].value /* NULL deref */\n\nIndependently, free_creds: releases the partially decoded svc_cred\nwith a bare kfree(creds).  gssx_dec_linux_creds() installs a\ngroups_alloc() result into creds-\u003ecr_group_info; that object is\nkvmalloc-backed and refcounted, and only put_group_info() reaches\nkvfree().  A plain kfree(creds) drops the wrapper and leaks the\ngroup_info allocation.\n\nThe natural fix for the leak is to call free_svc_cred(creds) before\nkfree(creds), but free_svc_cred() invokes put_group_info() on\ncreds-\u003ecr_group_info unconditionally when non-NULL.  The existing\nout_free_groups: path in gssx_dec_linux_creds() already called\ngroups_free() on that pointer without clearing it, so once\nfree_svc_cred() is wired in, the subsequent put_group_info() would\ntouch freed memory.\n\nFix all four together:\n\n  - Move the oa-\u003ecount = 1 assignment below the oa-\u003edata allocation\n    so it is never set when oa-\u003edata is NULL.\n  - Reset oa-\u003ecount to 0 at free_oa: so count and data stay\n    coherent and the caller sees an empty option array.\n  - Call free_svc_cred(creds) before kfree(creds) at free_creds:\n    so the refcounted cr_group_info is released.  free_svc_cred()\n    either NULL-guards each field explicitly (cr_group_info has\n    an if() check) or delegates to a helper that is NULL-safe\n    itself (kfree for the string fields, gss_mech_put() which\n    guards with if(gm) at gss_mech_switch.c:342), so it is safe\n    to call on a partially decoded svc_cred where only\n    cr_uid/cr_gid/cr_group_info have been written and everything\n    else is zero from kzalloc.\n  - In gssx_dec_linux_creds()'s out_free_groups: path, release\n    cr_group_info with put_group_info() rather than groups_free()\n    so the teardown matches free_svc_cred()'s refcount-aware path,\n    and clear the pointer so a later free_svc_cred() on the same\n    creds does not release it a second time.","modified":"2026-09-13T06:06:36Z","published":"2026-09-11T20:19:37Z","upstream":["CVE-2026-89544"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89544"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"6.6.150.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-100656.json"}}],"schema_version":"1.9.0"}