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rseq: Simplify registration

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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 <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://patch.msgid.link/20251027084306.274661227@linutronix.de
This commit is contained in:
Thomas Gleixner
2025-10-27 09:44:24 +01:00
committed by Ingo Molnar
parent 41b43a6ba3
commit 067b3b41b4
1 changed files with 3 additions and 7 deletions
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10
kernel/rseq.c
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@@ -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