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rseq: Set rseq::cpu_id_start to 0 on unregistration

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

Fixes: 0f085b4188 ("rseq: Provide and use rseq_set_ids()")
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Link: https://patch.msgid.link/20260428224427.271566313%40kernel.org
Cc: stable@vger.kernel.org
This commit is contained in:
Thomas Gleixner 2026-04-28 10:10:19 +02:00 committed by Peter Zijlstra
parent cb48828f06
commit 2cb68e4512
1 changed files with 9 additions and 11 deletions
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20
kernel/rseq.c
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@ -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))
return true;
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;
}