In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
SUNRPC: fix gssx_dec_option_array error path bugs<\/p>\n
Four 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.<\/p>\n
gssx_dec_option_array() sets oa->count = 1 before allocating
\noa->data. If that allocation fails, -ENOMEM is returned with
\noa->count == 1 and oa->data == NULL. All other error paths jump
\nto free_oa: which frees oa->data and NULLs it but also leaves
\noa->count == 1. The caller trusts the count:<\/p>\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 *\/<\/p>\n
Independently, free_creds: releases the partially decoded svc_cred
\nwith a bare kfree(creds). gssx_dec_linux_creds() installs a
\ngroups_alloc() result into creds->cr_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.<\/p>\n
The 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->cr_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.<\/p>\n
Fix all four together:<\/p>\n
– Move the oa->count = 1 assignment below the oa->data allocation
\n so it is never set when oa->data is NULL.
\n – Reset oa->count 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.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
SUNRPC: fix gssx_dec_option_array error path bugs<\/p>\n
Four coupled defects in the gssx XDR option-array decoder make the
\nerror paths u<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-21466","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/21466","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=21466"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=21466"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=21466"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}