From 067b3b41b4dd5bf51d6874206f5c1f72e0684eeb Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 27 Oct 2025 09:44:24 +0100 Subject: [PATCH] rseq: Simplify registration There is no point to read the critical section element in the newly registered user space RSEQ struct first in order to clear it. Just clear it and be done with it. Signed-off-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Mathieu Desnoyers Link: https://patch.msgid.link/20251027084306.274661227@linutronix.de --- kernel/rseq.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) diff --git a/kernel/rseq.c b/kernel/rseq.c index 51fafc4528b0f..80af48a972f06 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -492,11 +492,9 @@ void rseq_syscall(struct pt_regs *regs) /* * sys_rseq - setup restartable sequences for caller thread. */ -SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, - int, flags, u32, sig) +SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, int, flags, u32, sig) { int ret; - u64 rseq_cs; if (flags & RSEQ_FLAG_UNREGISTER) { if (flags & ~RSEQ_FLAG_UNREGISTER) @@ -557,11 +555,9 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, * avoid a potential segfault on return to user-space. The proper thing * to do would have been to fail the registration but this would break * older libcs that reuse the rseq area for new threads without - * clearing the fields. + * clearing the fields. Don't bother reading it, just reset it. */ - if (rseq_get_rseq_cs_ptr_val(rseq, &rseq_cs)) - return -EFAULT; - if (rseq_cs && clear_rseq_cs(rseq)) + if (put_user(0UL, &rseq->rseq_cs)) return -EFAULT; #ifdef CONFIG_DEBUG_RSEQ -- 2.47.3