From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 CACD7387593; Mon, 23 Mar 2026 14:43:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774277000; cv=none; b=fLyjSJnIt6AjpNPfWYHOAWjvqYILE/ML8cr4fjIr1JUo0EOC/H5u2sIvQbXrjRjJcd4kOZ70yELJTyREPq+mEmPLNSc61A4VrbCMLPMxxLMJHmkY+05i6jjV48OJDAWSbbl2Fbmp8llJMhHbhpcng8u7dxtezyls6ENk6zzVT+s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774277000; c=relaxed/simple; bh=tjz/uXlcYtFBZBGg1uf5qfwY2swGDdUB3UHvBp8sjSk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=NBCh3XcyQAIOZ5flUrw/0hW++hgLDWTyRXfFwS8Zr3Ami0wWwHA0pNF1J0zWWF6etGFathADL8c0WTTn2OGLHB6gNsTuSqyU/Gb218/+U74S1XCk5CahkkD8X0U3473XCdQe9NsA4SXEsJw+Y3w4BYt2dUDnMy57mP7ao/OQpLo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=n8nTsKDe; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="n8nTsKDe" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 60391C4CEF7; Mon, 23 Mar 2026 14:43:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1774277000; bh=tjz/uXlcYtFBZBGg1uf5qfwY2swGDdUB3UHvBp8sjSk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=n8nTsKDedLH/PsU5t+jxraWbDW4mgXuygt/tLl9bWfC+RjUmVLxVtugsRqXUQRfpx oXNZ4a1awdW5Hqry7AxLh79YcNfQImd9tas1nPzt7FBmMVDcFRdj50gHzBau9nZtdi GnvAdooUw6e043fxAFuH8xLEGf58EeTp+wgmzq90= 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 6.12 282/460] x86/uprobes: Fix XOL allocation failure for 32-bit tasks Date: Mon, 23 Mar 2026 14:44:38 +0100 Message-ID: <20260323134533.407124029@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260323134526.647552166@linuxfoundation.org> References: <20260323134526.647552166@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-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 @@ -1223,3 +1223,27 @@ 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 @@ -146,6 +146,7 @@ extern void arch_uprobe_copy_ixol(struct 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 { }; --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -1493,6 +1493,12 @@ static const struct vm_special_mapping x .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) { @@ -1508,9 +1514,7 @@ 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;