From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 0FD0B430BA1 for ; Mon, 2 Mar 2026 09:45:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772444724; cv=none; b=f6otqSZz/9Zp0zZ98Z4a4/LR4ZEHO5gNk5G3r1EoQeYaWLDPx0oowUR8dNhB3rqbQXz/O8k7GEMAmnxldMHS8ir4DYeUDiyriH6KIR2PKw0T7dasn6TbixB8WKAcVU5q3oEWg/QNhL0WUzWZcRNqILwcvqYqo2RrDKerUMT4t2U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772444724; c=relaxed/simple; bh=LoTwO3EeQS+4MjHXcMfxYZRi+8u5iJZGZBFTvyVt7Vg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=HuI0BPqpoouywH5cW1ilrj93ZCJHi9wfuIcsaNoZUjyQQwR2aN00JlVELjCSfZtveSMTt77DGtvwO2QSouAnNfqTTU4+0pjhZr7dmvKvRRvmwMcsSTEpFHffXY8tJakJMpG8nO6eBxRtxW5awBGxXJZA/teKubH5kkcIXM9brCM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=gNLr1yVQ; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="gNLr1yVQ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1772444722; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=yPtVXkP8KA5UW6r/Q7mKGuCwCo9/GepMlst5FcQcDt4=; b=gNLr1yVQEH9pSmkjefc6F8ihjtqNBuniQZ/OfRakV/TkIgxEAWDXgWkcZWCGmCag3w9uLY XMjfD7KlKTJqD/YQFaRiZZf7Ezg319TYs7ezKXRyMsUOGh+o9j768tSmpNbcMmjWerNpCF N8++g9oY9QNAdCReYJ8V0J/MUt9GTHM= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-14-o2-0LF2ZO9ichR68xRjLMw-1; Mon, 02 Mar 2026 04:45:18 -0500 X-MC-Unique: o2-0LF2ZO9ichR68xRjLMw-1 X-Mimecast-MFC-AGG-ID: o2-0LF2ZO9ichR68xRjLMw_1772444717 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A7C4E1956058; Mon, 2 Mar 2026 09:45:17 +0000 (UTC) Received: from fedora (unknown [10.45.224.37]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 983871800598; Mon, 2 Mar 2026 09:45:14 +0000 (UTC) Received: by fedora (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 2 Mar 2026 10:45:17 +0100 (CET) Date: Mon, 2 Mar 2026 10:45:12 +0100 From: Oleg Nesterov To: Sasha Levin Cc: stable@vger.kernel.org, Paulo Andrade , "Peter Zijlstra (Intel)" , linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org Subject: Re: FAILED: Patch "x86/uprobes: Fix XOL allocation failure for 32-bit tasks" failed to apply to 6.18-stable tree Message-ID: References: <20260301011537.1669125-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260301011537.1669125-1-sashal@kernel.org> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 On 02/28, Sasha Levin wrote: > > The patch below does not apply to the 6.18-stable tree. > If someone wants it applied there, or to any other stable or longterm > tree, then please email the backport, including the original git commit > id to . I never know how to react to "failed to apply to stabe" emails. I am going to send [PATCH 6.18.y] in reply to this email. Is it OK? Oleg. > Thanks, > Sasha > > ------------------ original commit in Linus's tree ------------------ > > From d55c571e4333fac71826e8db3b9753fadfbead6a Mon Sep 17 00:00:00 2001 > From: Oleg Nesterov > Date: Sun, 11 Jan 2026 16:00:37 +0100 > Subject: [PATCH] x86/uprobes: Fix XOL allocation failure for 32-bit tasks > > This script > > #!/usr/bin/bash > > echo 0 > /proc/sys/kernel/randomize_va_space > > echo 'void main(void) {}' > TEST.c > > # -fcf-protection to ensure that the 1st endbr32 insn can't be emulated > gcc -m32 -fcf-protection=branch TEST.c -o test > > bpftrace -e 'uprobe:./test:main {}' -c ./test > > "hangs", the probed ./test task enters an endless loop. > > The problem is that with randomize_va_space == 0 > get_unmapped_area(TASK_SIZE - PAGE_SIZE) called by xol_add_vma() can not > just return the "addr == TASK_SIZE - PAGE_SIZE" hint, this addr is used > by the stack vma. > > arch_get_unmapped_area_topdown() doesn't take TIF_ADDR32 into account and > in_32bit_syscall() is false, this leads to info.high_limit > TASK_SIZE. > vm_unmapped_area() happily returns the high address > TASK_SIZE and then > get_unmapped_area() returns -ENOMEM after the "if (addr > TASK_SIZE - len)" > check. > > handle_swbp() doesn't report this failure (probably it should) and silently > restarts the probed insn. Endless loop. > > I think that the right fix should change the x86 get_unmapped_area() paths > to rely on TIF_ADDR32 rather than in_32bit_syscall(). Note also that if > CONFIG_X86_X32_ABI=y, in_x32_syscall() falsely returns true in this case > because ->orig_ax = -1. > > But we need a simple fix for -stable, so this patch just sets TS_COMPAT if > the probed task is 32-bit to make in_ia32_syscall() true. > > Fixes: 1b028f784e8c ("x86/mm: Introduce mmap_compat_base() for 32-bit mmap()") > Reported-by: Paulo Andrade > Signed-off-by: Oleg Nesterov > Signed-off-by: Peter Zijlstra (Intel) > Link: https://lore.kernel.org/all/aV5uldEvV7pb4RA8@redhat.com/ > Cc: stable@vger.kernel.org > Link: https://patch.msgid.link/aWO7Fdxn39piQnxu@redhat.com > --- > arch/x86/kernel/uprobes.c | 24 ++++++++++++++++++++++++ > include/linux/uprobes.h | 1 + > kernel/events/uprobes.c | 10 +++++++--- > 3 files changed, 32 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c > index 7be8e361ca55b..619dddf54424e 100644 > --- a/arch/x86/kernel/uprobes.c > +++ b/arch/x86/kernel/uprobes.c > @@ -1823,3 +1823,27 @@ bool is_uprobe_at_func_entry(struct pt_regs *regs) > > return false; > } > + > +#ifdef CONFIG_IA32_EMULATION > +unsigned long arch_uprobe_get_xol_area(void) > +{ > + struct thread_info *ti = current_thread_info(); > + unsigned long vaddr; > + > + /* > + * HACK: we are not in a syscall, but x86 get_unmapped_area() paths > + * ignore TIF_ADDR32 and rely on in_32bit_syscall() to calculate > + * vm_unmapped_area_info.high_limit. > + * > + * The #ifdef above doesn't cover the CONFIG_X86_X32_ABI=y case, > + * but in this case in_32bit_syscall() -> in_x32_syscall() always > + * (falsely) returns true because ->orig_ax == -1. > + */ > + if (test_thread_flag(TIF_ADDR32)) > + ti->status |= TS_COMPAT; > + vaddr = get_unmapped_area(NULL, TASK_SIZE - PAGE_SIZE, PAGE_SIZE, 0, 0); > + ti->status &= ~TS_COMPAT; > + > + return vaddr; > +} > +#endif > diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h > index ee3d36eda45dd..f548fea2adec8 100644 > --- a/include/linux/uprobes.h > +++ b/include/linux/uprobes.h > @@ -242,6 +242,7 @@ extern void arch_uprobe_clear_state(struct mm_struct *mm); > extern void arch_uprobe_init_state(struct mm_struct *mm); > extern void handle_syscall_uprobe(struct pt_regs *regs, unsigned long bp_vaddr); > extern void arch_uprobe_optimize(struct arch_uprobe *auprobe, unsigned long vaddr); > +extern unsigned long arch_uprobe_get_xol_area(void); > #else /* !CONFIG_UPROBES */ > struct uprobes_state { > }; > diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c > index a7d7d83ca1d78..dfbce021fb027 100644 > --- a/kernel/events/uprobes.c > +++ b/kernel/events/uprobes.c > @@ -1694,6 +1694,12 @@ static const struct vm_special_mapping xol_mapping = { > .mremap = xol_mremap, > }; > > +unsigned long __weak arch_uprobe_get_xol_area(void) > +{ > + /* Try to map as high as possible, this is only a hint. */ > + return get_unmapped_area(NULL, TASK_SIZE - PAGE_SIZE, PAGE_SIZE, 0, 0); > +} > + > /* Slot allocation for XOL */ > static int xol_add_vma(struct mm_struct *mm, struct xol_area *area) > { > @@ -1709,9 +1715,7 @@ static int xol_add_vma(struct mm_struct *mm, struct xol_area *area) > } > > if (!area->vaddr) { > - /* Try to map as high as possible, this is only a hint. */ > - area->vaddr = get_unmapped_area(NULL, TASK_SIZE - PAGE_SIZE, > - PAGE_SIZE, 0, 0); > + area->vaddr = arch_uprobe_get_xol_area(); > if (IS_ERR_VALUE(area->vaddr)) { > ret = area->vaddr; > goto fail; > -- > 2.51.0 > > > >