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 8658521B191; Sat, 30 May 2026 17:43:36 +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=1780163017; cv=none; b=i+6jp6P/9+M9rZqWRVtzk+MUVd6DnnB4dJNAO4z/rxPG4kKMLYq05H1MAKnukF/rLc6mCbxobWC0ZYYKArxddtOb7ZxGLbwDVhCP9+kh8hv+MZScWmaGEib9jvVEGO2wx3Ur4pp30qozT9CXV0nGR+B9fxvEZkEdFkI6/7QvQYo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780163017; c=relaxed/simple; bh=vqlsMw16Sy8neNTLWf6WjqUbOvguk/YplNOcFtwV4Jc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=evGAMhpPghq5kwR0HVQhVIQL6d7nOBbnhIcYlH32TjY39meuW04CsKxDI7ogedQbXmdLXg4NFbWHggSiSpbbtgW72PaIozivGJvYtakh+EK9zKphltGpQ4SoWqB4cUuCXYFYZMc8QWTK+s7yGxNqB1JoMs+6lXwGVK/Z5mJYAmo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=lRJg0k7h; 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="lRJg0k7h" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8D9461F00893; Sat, 30 May 2026 17:43:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1780163016; bh=BCh0DlUvPDMy7ERRW9R3KgP1LSCcIN5H3X+YiUzW/Wo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=lRJg0k7h/2xf2Ujz13HY6WzyUagRS8OZNkld6GeuiEZLJjSN/i9DWLy9J4t5eysgv YCgl5IHgsgHAXt3kIkRu9wUXuSBnUaprgyKagV3cwf6ZiOCbnXOoVIREuLXgjW8a5t 0G12a7sYZxQB4JWRREHnyOPno5xhkagg01n+zvgQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org, Sasha Levin Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Paulo Andrade , Oleg Nesterov , "Peter Zijlstra (Intel)" Subject: [PATCH 5.15 131/776] x86/uprobes: Fix XOL allocation failure for 32-bit tasks Date: Sat, 30 May 2026 17:57:25 +0200 Message-ID: <20260530160243.786168891@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260530160240.228940103@linuxfoundation.org> References: <20260530160240.228940103@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Oleg Nesterov [ 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 Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/uprobes.c | 24 ++++++++++++++++++++++++ include/linux/uprobes.h | 1 + kernel/events/uprobes.c | 10 +++++++--- 3 files changed, 32 insertions(+), 3 deletions(-) --- a/arch/x86/kernel/uprobes.c +++ b/arch/x86/kernel/uprobes.c @@ -1097,3 +1097,27 @@ bool arch_uretprobe_is_alive(struct retu 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 --- a/include/linux/uprobes.h +++ b/include/linux/uprobes.h @@ -138,6 +138,7 @@ extern bool arch_uretprobe_is_alive(stru extern bool arch_uprobe_ignore(struct arch_uprobe *aup, struct pt_regs *regs); extern void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr, void *src, unsigned long len); +extern unsigned long arch_uprobe_get_xol_area(void); #else /* !CONFIG_UPROBES */ struct uprobes_state { }; --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -1437,6 +1437,12 @@ void uprobe_munmap(struct vm_area_struct set_bit(MMF_RECALC_UPROBES, &vma->vm_mm->flags); } +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) { @@ -1452,9 +1458,7 @@ static int xol_add_vma(struct mm_struct } 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;