Commit 2cb68e45 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Peter Zijlstra
Browse files

rseq: Set rseq::cpu_id_start to 0 on unregistration 



The RSEQ rework changed that to RSEQ_CPU_UNINITILIZED, which is obviously
incompatible. Revert back to the original behavior.

Fixes: 0f085b41 ("rseq: Provide and use rseq_set_ids()")
Reported-by: default avatarDmitry Vyukov <dvyukov@google.com>
Signed-off-by: default avatarThomas Gleixner <tglx@kernel.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarDmitry Vyukov <dvyukov@google.com>
Tested-by: default avatarDmitry Vyukov <dvyukov@google.com>
Link: https://patch.msgid.link/20260428224427.271566313%40kernel.org
Cc: stable@vger.kernel.org
parent cb48828f

kernel/rseq.c

+9 −11
Original line number Diff line number Diff line
@@ -236,11 +236,6 @@ static int __init rseq_debugfs_init(void) 
}

__initcall(rseq_debugfs_init);



static bool rseq_set_ids(struct task_struct *t, struct rseq_ids *ids, u32 node_id)

{

	return rseq_set_ids_get_csaddr(t, ids, node_id, NULL);

}



static bool rseq_handle_cs(struct task_struct *t, struct pt_regs *regs)

{

	struct rseq __user *urseq = t->rseq.usrptr;
@@ -384,19 +379,22 @@ void rseq_syscall(struct pt_regs *regs) 


static bool rseq_reset_ids(void)

{

	struct rseq_ids ids = {

		.cpu_id		= RSEQ_CPU_ID_UNINITIALIZED,

		.mm_cid		= 0,

	};

	struct rseq __user *rseq = current->rseq.usrptr;



	/*

	 * If this fails, terminate it because this leaves the kernel in

	 * stupid state as exit to user space will try to fixup the ids

	 * again.

	 */

	if (rseq_set_ids(current, &ids, 0))

	scoped_user_rw_access(rseq, efault) {

		unsafe_put_user(0, &rseq->cpu_id_start, efault);

		unsafe_put_user(RSEQ_CPU_ID_UNINITIALIZED, &rseq->cpu_id, efault);

		unsafe_put_user(0, &rseq->node_id, efault);

		unsafe_put_user(0, &rseq->mm_cid, efault);

	}

	return true;



efault:

	force_sig(SIGSEGV);

	return false;

}