From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E0FB940926D; Tue, 21 Jul 2026 18:52:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784659939; cv=none; b=RWy6BSJDCqavMrJRih5siWq/64RKIKY0DNYgUQr6MIQErogAB4ip8QDk6Nr7saXfkWm9jQGI1JrUNuwKxa/Q9nilOAdh6SrKRpuzlNINneu0VF/3I85DZP8X9LdmhJ/EUYDQRjNHNFCW/KbxmOzGxtYZ+gsdCNsb40eKoaf90Fw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784659939; c=relaxed/simple; bh=HfjxCNvi+1yeGtrw0gcyMXi1ys2DA4Yh69dciV/cY+M=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=r9GmrqeP5JcDep25CthnV2g8tPZwwpzJI4ANnQI6VyekfsAxwkijOA+EICbXwh1scQsxZPdIYMKm+JTckd016TvrC3TIvA+NGDqNZSA6mzK+hHgg4KGqMi/eygmXis2H24n07nCxgSq8gZQrDKVbV6eM0m+zb0C+bfz8JgGLqUU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ChYJd0q1; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="ChYJd0q1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 52ED91F000E9; Tue, 21 Jul 2026 18:52:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784659937; bh=lXWJhcIo8GLN9NH3xAg8zxoHFrwAr7bo7YI5QTjinIU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ChYJd0q1ci6HxbzeP9dYEHrusm8LbK78ll8ZCO6KUWCcWK9b6kAzhHjam/q0Tip59 A1YmvQbTuegxb3Toiys6Hc1NQXM1YIZemWODLlc1OB2NPDyc70QG967Dd7SSdR/dQP 02da42Coifc9C4O+Lc3bA5CmeQ6t1KX+dod1iwXs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Aboorva Devarajan , Shrikanth Hegde , Madhavan Srinivasan , Sasha Levin Subject: [PATCH 7.1 0791/2077] powerpc/kexec: fix double get_cpu() imbalance in kexec_prepare_cpus Date: Tue, 21 Jul 2026 17:07:44 +0200 Message-ID: <20260721152611.451996130@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152552.646164743@linuxfoundation.org> References: <20260721152552.646164743@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Aboorva Devarajan [ Upstream commit 5c86f1c1f972761a04bf22f4c0618d1aa714185b ] kexec_prepare_cpus_wait() calls get_cpu() internally to obtain the current CPU id. kexec_prepare_cpus() calls kexec_prepare_cpus_wait() twice -- once for KEXEC_STATE_IRQS_OFF and once for KEXEC_STATE_REAL_MODE -- but only issues a single put_cpu() at the end, leaving preempt_count elevated by one extra nesting level. In practice the imbalance does not trigger a 'scheduling while atomic' splat because the kexec path is a one-way trip: IRQs are already disabled, no schedule() occurs after the leak, and default_machine_kexec() overwrites preempt_count with HARDIRQ_OFFSET before jumping into kexec_sequence() which never returns. However the bookkeeping is still wrong. kexec_prepare_cpus() calls local_irq_disable()/hard_irq_disable() before invoking kexec_prepare_cpus_wait(), so the CPU is already pinned and the get_cpu()/put_cpu() preempt_disable() bracketing is unnecessary. Only the current CPU id is needed, so replace get_cpu() with raw_smp_processor_id() and drop the now-unneeded put_cpu(). Fixes: 1fc711f7ffb0 ("powerpc/kexec: Fix race in kexec shutdown") Signed-off-by: Aboorva Devarajan Reviewed-by: Shrikanth Hegde Signed-off-by: Madhavan Srinivasan Link: https://patch.msgid.link/20260605082912.305100-4-aboorvad@linux.ibm.com Signed-off-by: Sasha Levin --- arch/powerpc/kexec/core_64.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/arch/powerpc/kexec/core_64.c b/arch/powerpc/kexec/core_64.c index 825ab8a88f18e6..58c13a59b93b58 100644 --- a/arch/powerpc/kexec/core_64.c +++ b/arch/powerpc/kexec/core_64.c @@ -169,7 +169,7 @@ static void kexec_prepare_cpus_wait(int wait_state) int my_cpu, i, notified=-1; hw_breakpoint_disable(); - my_cpu = get_cpu(); + my_cpu = raw_smp_processor_id(); /* Make sure each CPU has at least made it to the state we need. * * FIXME: There is a (slim) chance of a problem if not all of the CPUs @@ -267,8 +267,6 @@ static void kexec_prepare_cpus(void) /* after we tell the others to go down */ if (ppc_md.kexec_cpu_down) ppc_md.kexec_cpu_down(0, 0); - - put_cpu(); } #else /* ! SMP */ -- 2.53.0