[PATCH RESEND sched_ext/for-7.2] sched_ext: Use offsetofend on both sides of the ops_cid layout assert

[Tejun Heo]

sizeof() includes trailing struct pad, offsetofend() doesn't. On
32-bit PPC, sched_ext_ops_cid tail-pads 4 bytes past @priv and the
assert trips. Use offsetofend() on both sides.

Reported-by: kernel test robot <lkp@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-kbuild-all/202605081637.DbH4SZ1E-lkp@xxxxxxxxx/
Fixes: 7e655ed7b953 ("sched_ext: Add bpf_sched_ext_ops_cid struct_ops type")
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
---
 kernel/sched/ext.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 7ac7d10a41be..f86ee15be7cb 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -10380,9 +10380,11 @@ static int __init scx_init(void)
 	/*
 	 * cid-form must end exactly at @priv - validate_ops() skips
 	 * cpu_acquire/cpu_release for cid-form because reading those fields
-	 * past the BPF allocation would be UB.
+	 * past the BPF allocation would be UB. offsetofend() on both sides
+	 * instead of sizeof() on sched_ext_ops_cid to sidestep trailing
+	 * struct padding (e.g. 32-bit PPC tail-pads ops_cid past @priv).
 	 */
-	BUILD_BUG_ON(sizeof(struct sched_ext_ops_cid) !=
+	BUILD_BUG_ON(offsetofend(struct sched_ext_ops_cid, priv) !=
 		     offsetofend(struct sched_ext_ops, priv));
 #undef CID_OFFSET_MATCH
 
-- 
2.54.0