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 5327C333434 for ; Mon, 2 Mar 2026 09:46:16 +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=1772444778; cv=none; b=u0ibvDKbZgDGPHjcF+AOK3rpAt6mEkrOq4oBS0SZgdKHpp17ijriVMi/e3D/dmbr/cyrUDpod6XRdV5KiECjWlaNEVFHuxQqBRvk+0jRK7fOJ1JGzl4JZbksHCGd0ffSvUbWnSuVEi/wLOmjG8x6saxIRDWahU9xcLcLrYnKAmQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772444778; c=relaxed/simple; bh=AdN5BIKqvaD/m+CfD/B1gdDrBp6A2Pyn3P3Wg3pT75A=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=m9IR3axCJBIkoSJ2Eillke8+DD8haTJV4tWSZKv+Vi1rc4zNRFA27FuzjJDJ38M7oZ58NSQbLnHZrgRktAy0pqKnoCZIoLZRj1cxQVn0rHAUrB0uUOKedBWWHjTxkKi+iO5Mf0VQJscRxcG27OWia6Ohg415RiEabHrfTni1Kh0= 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=K1bUHAyo; 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="K1bUHAyo" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1772444776; 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=BBWL7AkeE2fO9iOHWP24JjF/LvZ0Uocj4yyy3v7eU9Y=; b=K1bUHAyouIcw9g5RQ3+cG2y2b8ZTogc9O7Gi04ybOBNKkfmaBEaTZGr0NgJ8j/7sTbyNOV i9FnADMbOtggeTe4nybYaRQt5e/VvPMl11sgBJEycEBiuZVLKIpghhwfJmEcrQEU6I5H+M 4ObWbuZi/hTCstXUxVU7gxkfsqv6V68= Received: from mx-prod-mc-01.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-561-L1Lm3fTLPG-he5WeyQJvPg-1; Mon, 02 Mar 2026 04:46:08 -0500 X-MC-Unique: L1Lm3fTLPG-he5WeyQJvPg-1 X-Mimecast-MFC-AGG-ID: L1Lm3fTLPG-he5WeyQJvPg_1772444767 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (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-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 567BE1956095; Mon, 2 Mar 2026 09:46:07 +0000 (UTC) Received: from fedora (unknown [10.45.224.37]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 0131A1956053; Mon, 2 Mar 2026 09:46:04 +0000 (UTC) Received: by fedora (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 2 Mar 2026 10:46:06 +0100 (CET) Date: Mon, 2 Mar 2026 10:45:57 +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 6.18.y] x86/uprobes: Fix XOL allocation failure for 32-bit tasks 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 3.0 on 10.30.177.17 [ 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 845aeaf36b8d..73be14736062 100644 --- a/arch/x86/kernel/uprobes.c +++ b/arch/x86/kernel/uprobes.c @@ -1819,3 +1819,27 @@ 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 ee3d36eda45d..f548fea2adec 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 f11ceb8be8c4..4e45236064dc 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; -- 2.52.0