From nobody Sun Feb 8 06:56:23 2026 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 D7C8432AACE; Fri, 16 Jan 2026 10:50:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768560606; cv=none; b=LCCztAKfBRGNW6uu25YFZtYhpbFpagVeylDgTxw1hqkLb+1jhxBq00MgzwBnSYsu2gSygHNdoROUy3qc4R7+GSVrIqrfITIeHcXTKH/8QQ3dCcGL6np9Vp/c1H+CLDhJtqfWMdA6VM/aVbrKke1p2OFXIqwoDU5G7oKqMRrxGkc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768560606; c=relaxed/simple; bh=XOaluGgtJlQu5fRibfyDjhPGTHZwgCyDnepWxVFHI9c=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=SPqK6U4Srgj84DW3Q9kE1v4xiWqs7XxgG0qIM+pFcrr3Yr2zjt0GAJuHYrTWWLN7V5P5DaWxInMKS2ADWCAKJ93E+qHdaWrGxcYxXGRO+W2ml6uzTQFSnZ6lOh3fbvTy0shjXO0nAxNb6niZCD8JSI514Bv3uja2M0f3dc44Fd4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=ifFzQVgQ; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=EmU5w9rp; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="ifFzQVgQ"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="EmU5w9rp" Date: Fri, 16 Jan 2026 10:49:51 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1768560596; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+AoGx+78koCEd4Ozrx9VquzV+QrGliPdSLjVLeyNCB8=; b=ifFzQVgQq7HsimgsNG/0nP9dyCZ3TfGEJYcfugQFxZ+hrBbzMN1wZJ7lqKyrFYFBePDBTk +6+ALwktL0dyAeMjkS+u1jBGbKBrNGw3jUlkSTkkA2nIKAVmSWLhjfTOyHrjM4VMGVKn9q BhHN8HHrXOAYPqCwbsRJvLTzvXv5zuqDwzeMRzVl2ObMLPCYhC4ZZGcKfhLBlLjFww2MeJ 0RX8zE1Qfgix+kgQQ889TrGxG3dCa+bAtiBoDT3d1fxIpi0bKQv5hA77pDYYdx5FQHMsum kXe0/0Xi/MK+0bX5v8/4aBan9/rqOG7V6BNXFYit0hov8jxBtPpfuuumqr3g8w== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1768560596; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+AoGx+78koCEd4Ozrx9VquzV+QrGliPdSLjVLeyNCB8=; b=EmU5w9rpvQS2HYqM/0NCOAFcgQG0zQw8dsOWr6XJK/jUMUd7WhFggZd9KaIjFaDELmtJhc WfbFrullNkC5p1Dg== From: "tip-bot2 for Oleg Nesterov" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: perf/core] x86/uprobes: Fix XOL allocation failure for 32-bit tasks Cc: Paulo Andrade , Oleg Nesterov , "Peter Zijlstra (Intel)" , stable@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <176856059167.510.9955645112386260072.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Precedence: bulk Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable The following commit has been merged into the perf/core branch of tip: Commit-ID: 40bb50531482258bf410d84fa4ecb944e02b887b Gitweb: https://git.kernel.org/tip/40bb50531482258bf410d84fa4ecb944e= 02b887b Author: Oleg Nesterov AuthorDate: Sun, 11 Jan 2026 16:00:37 +01:00 Committer: Peter Zijlstra CommitterDate: Fri, 16 Jan 2026 11:46:25 +01:00 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=3Dbranch 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 =3D=3D 0 get_unmapped_area(TASK_SIZE - PAGE_SIZE) called by xol_add_vma() can not just return the "addr =3D=3D 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=3Dy, in_x32_syscall() falsely returns true in this case because ->orig_ax =3D -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 ("86/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 7be8e36..619dddf 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) =20 return false; } + +#ifdef CONFIG_IA32_EMULATION +unsigned long arch_uprobe_get_xol_area(void) +{ + struct thread_info *ti =3D 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=3Dy case, + * but in this case in_32bit_syscall() -> in_x32_syscall() always + * (falsely) returns true because ->orig_ax =3D=3D -1. + */ + if (test_thread_flag(TIF_ADDR32)) + ti->status |=3D TS_COMPAT; + vaddr =3D get_unmapped_area(NULL, TASK_SIZE - PAGE_SIZE, PAGE_SIZE, 0, 0); + ti->status &=3D ~TS_COMPAT; + + return vaddr; +} +#endif diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h index ee3d36e..f548fea 100644 --- a/include/linux/uprobes.h +++ b/include/linux/uprobes.h @@ -242,6 +242,7 @@ extern void arch_uprobe_clear_state(struct mm_struct *m= m); extern void arch_uprobe_init_state(struct mm_struct *mm); extern void handle_syscall_uprobe(struct pt_regs *regs, unsigned long bp_v= addr); extern void arch_uprobe_optimize(struct arch_uprobe *auprobe, unsigned lon= g 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 a7d7d83..dfbce02 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -1694,6 +1694,12 @@ static const struct vm_special_mapping xol_mapping = =3D { .mremap =3D xol_mremap, }; =20 +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 x= ol_area *area) } =20 if (!area->vaddr) { - /* Try to map as high as possible, this is only a hint. */ - area->vaddr =3D get_unmapped_area(NULL, TASK_SIZE - PAGE_SIZE, - PAGE_SIZE, 0, 0); + area->vaddr =3D arch_uprobe_get_xol_area(); if (IS_ERR_VALUE(area->vaddr)) { ret =3D area->vaddr; goto fail;