[PATCH] nvmet-auth: fix out-of-bounds write in nvmet_auth_challenge()

[Weiming Shi <bestswngs@gmail.com>]

nvmet_auth_challenge() receives its output buffer as a void pointer.
sizeof(*d) therefore evaluates to one with GCC and undercounts the fixed
challenge header by 15 bytes.  A short AUTH_RECEIVE buffer can pass the
check before the challenge is copied past the end of its allocation.

Use the typed challenge pointer when calculating the response size.

  BUG: KASAN: slab-out-of-bounds in nvmet_execute_auth_receive (drivers/nvme/target/fabrics-cmd-auth.c:442 drivers/nvme/target/fabrics-cmd-auth.c:569)
  Write of size 32 by task kworker/1:1H/64
  Workqueue: nvmet_tcp_wq nvmet_tcp_io_work
  Call Trace:
  nvmet_execute_auth_receive (drivers/nvme/target/fabrics-cmd-auth.c:442 drivers/nvme/target/fabrics-cmd-auth.c:569)
  nvmet_tcp_try_recv_pdu (drivers/nvme/target/tcp.c:1119 drivers/nvme/target/tcp.c:1243)
  nvmet_tcp_io_work (drivers/nvme/target/tcp.c:1350 drivers/nvme/target/tcp.c:1382 drivers/nvme/target/tcp.c:1445)
  process_one_work (kernel/workqueue.c:3322)
  worker_thread (kernel/workqueue.c:3405 kernel/workqueue.c:3486)
  kthread (kernel/kthread.c:436)
  ret_from_fork (arch/x86/kernel/process.c:158)
  ret_from_fork_asm (arch/x86/entry/entry_64.S:245)
  The buggy address is located 16 bytes inside of
   allocated 33-byte region [ffff888000554e80, ffff888000554ea1)
  Kernel panic - not syncing: KASAN: panic_on_warn set ...

Cc: stable@vger.kernel.org
Fixes: db1312dd9548 ("nvmet: implement basic In-Band Authentication")
Reported-by: co+77553a7fc66ac133@bugs.sh
Closes: https://lore.kernel.org/all/Ah6QavQXwvshtqyUcYD1P1R7XE0ND9fB7lbV@bugs.sh/
Assisted-by: Codex:gpt-5.6
Signed-off-by: Weiming Shi <bestswngs@gmail.com>
---
 drivers/nvme/target/fabrics-cmd-auth.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nvme/target/fabrics-cmd-auth.c b/drivers/nvme/target/fabrics-cmd-auth.c
index 92f8a76f10..dccdb55a36 100644
--- a/drivers/nvme/target/fabrics-cmd-auth.c
+++ b/drivers/nvme/target/fabrics-cmd-auth.c
@@ -427,7 +427,7 @@ static int nvmet_auth_challenge(struct nvmet_req *req, void *d, int al)
 	struct nvmet_ctrl *ctrl = req->sq->ctrl;
 	int ret = 0;
 	int hash_len = nvme_auth_hmac_hash_len(ctrl->shash_id);
-	int data_size = sizeof(*d) + hash_len;
+	int data_size = sizeof(*data) + hash_len;
 
 	if (ctrl->dh_tfm)
 		data_size += ctrl->dh_keysize;
-- 
2.55.0