From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 5CD6840B6F1 for ; Mon, 2 Mar 2026 15:14:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772464476; cv=none; b=QTG3r8HX4nct32NgRwCwtPEeD1RmUhMyhNaU5euihpAyq2msC2MB5C4teksalvGJdv9KFHe/gMM5c3DWeAkfeo7iqIHVMWppjSCubmhzoVQzdxEG7lSps+RHYhz1iY6oVgV2cV1tm8KU5qQNC8pQumNKbnjjrB85+U8wqV6U8yU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772464476; c=relaxed/simple; bh=HKZRcSRAOXVOFB8CLIC5vgmIzc89fmsHnsdGjPNHH64=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=X6VROC/d85YkCGLkYv5GCWE1kghioInayY9DI8/E/Z9o1zP9pINKeLCI5Z1z1XH//5zm5OOSWAfdG5XyIHu4IBCzVtXBnEDCugELKce4fR9F9xiFrXpzThx/ZjLrQ2eX9dBowiZII8e+9SnWGRrxkl2Js2p14wkw4BDF2RLeVVo= 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=HQhIyJuZ; arc=none smtp.client-ip=170.10.129.124 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="HQhIyJuZ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1772464474; 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=8zzTG2R0eOCQTbAfQXWXLurUXdad//xQ9kMoH+SbIJw=; b=HQhIyJuZea1Q1bKfORmLcVyFn8pRuFtki3hjVOD8NFwBdch27Ho2RCGgMGtQIxG+IUZXL/ FEZxM2YjBaEzfa4ftgqoUt9PRpKiwCS5vezn2rBsZEsoFC3sSPctSeXXhOWlOoDuZc45EI TPFWyUEgYetrvXQDo4G2HA5VVFA99WY= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-569-GzuSfCDNMM6CiBHW8i-GTQ-1; Mon, 02 Mar 2026 10:14:33 -0500 X-MC-Unique: GzuSfCDNMM6CiBHW8i-GTQ-1 X-Mimecast-MFC-AGG-ID: GzuSfCDNMM6CiBHW8i-GTQ_1772464472 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D35F21800869; Mon, 2 Mar 2026 15:14:31 +0000 (UTC) Received: from fedora (unknown [10.45.224.37]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 129FC19560B2; Mon, 2 Mar 2026 15:14:28 +0000 (UTC) Received: by fedora (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 2 Mar 2026 16:14:31 +0100 (CET) Date: Mon, 2 Mar 2026 16:14:27 +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: [PATCH 6.12.y] x86/uprobes: Fix XOL allocation failure for 32-bit tasks Message-ID: References: <20260301012146.1677811-1-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: <20260301012146.1677811-1-sashal@kernel.org> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 [ Upstream commit d55c571e4333fac71826e8db3b9753fadfbead6a ] 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 9194695662b2..6abb25ca9cd1 100644 --- a/arch/x86/kernel/uprobes.c +++ b/arch/x86/kernel/uprobes.c @@ -1223,3 +1223,27 @@ bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx, else return regs->sp <= ret->stack; } + +#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 d0cb0e02cd6a..34be2d579045 100644 --- a/include/linux/uprobes.h +++ b/include/linux/uprobes.h @@ -146,6 +146,7 @@ extern void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr, extern void uprobe_handle_trampoline(struct pt_regs *regs); extern void *arch_uprobe_trampoline(unsigned long *psize); extern unsigned long uprobe_get_trampoline_vaddr(void); +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 e30c4dd345f4..80cd12eb5854 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -1496,6 +1496,12 @@ static const struct vm_special_mapping xol_mapping = { .fault = xol_fault, }; +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) { @@ -1511,9 +1517,7 @@ 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; -- 2.52.0