drm/vmwgfx: skip hash_del_rcu when validation context has no hash table

vmw_validation_add_resource() calls hash_add_rcu() only when
ctx->sw_context is non-NULL, but the doomed-resource error path calls
hash_del_rcu() unconditionally.  The validation contexts declared with
DECLARE_VAL_CONTEXT(_, NULL, 0) in vmwgfx_kms.c, vmwgfx_scrn.c,
vmwgfx_stdu.c and vmwgfx_execbuf.c consequently reach a delete for a
node that was never added to any hash chain.

That is harmless today, but only incidentally so.  hash_del_rcu() is
hlist_del_init_rcu(), which is guarded by hlist_unhashed(), and
vmw_validation_mem_alloc() hands out memory from __GFP_ZERO pages that
are never recycled within a context's lifetime, so
node->hash.head.pprev is always NULL and the delete does nothing.
Neither property is apparent at the call site, and the asymmetry with
the add side invites a real bug the first time either one changes.

Mirror the condition from the add side so the node is only unlinked
when it was actually linked.  No functional change.

Assisted-by: Claude:claude-opus-4.7
Signed-off-by: Zack Rusin <zack.rusin@broadcom.com>
Reviewed-by: Ian Forbes <ian.forbes@broadcom.com>
Link: https://patch.msgid.link/20260505222728.519626-11-zack.rusin@broadcom.com

0 files changed, 0 insertions, 0 deletions