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 7E11B3F9AD2; Sat, 28 Feb 2026 17:42:58 +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=1772300578; cv=none; b=gftcsCWVDTisU2ZY9wPvTpCtkRauKeOs3gip6VhzoQfKKAI7R6zSf9/no0RKlsn+gC+nepiX8sJZFG1GCas0N72foAur0CoEdqiaqqrjoku9mYK91sY0kHKAeQYxBrHYwtbGTI4YZ5TNCB3pFX3XlO6DCw40Jwi0JuCPl2+Xcms= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772300578; c=relaxed/simple; bh=hA+DYSRYKtLUOo1IIuD02yY0aD61JcSOLCGFa/5OB4Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=bIdTdT5Uzn64RIkzyYPgkVHBfcWDwBtgHE3isxXWhlgykYh2YhN2nOTLvM3Lqza+xepSFoEt19U3OWF2o7FGKcDyXNZIz5YixtTPiHmYUP9bLqVAKMAZHz9qekOHo3H7ZgagdAtd0wf9LqpR25aogbTTayL9qXpqjSq8GO5ivLc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=uvIY/0eE; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="uvIY/0eE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B4986C19423; Sat, 28 Feb 2026 17:42:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772300578; bh=hA+DYSRYKtLUOo1IIuD02yY0aD61JcSOLCGFa/5OB4Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uvIY/0eE9RkbVRPPCDrUuQYWjph7GBTAl8q98TAPNSgnwHBpQiCuhqjxk+zmJ/o4Q mF1q6AN/gVtP+wXFDT/7I+DBid4L/g5Pe6zp8ZPHTvXGJg30Mr87D+7xxR7ZOzkwfU PtB4VtG7+FnXKmzO3kGVS4n/0+FI9ueMLbEIHOgXh473xMiw7F2fYlghBaFcefD2vO Opw3gRD8JsFQlZYwMgNi3wfGACbYvYAwgL4hkXB4h6boIEfpasze6UT+TyimfPe6K4 4gagxc6Cc0BZEtuwgQcTnmieGpBkwtYJEI0rfWIFsFTfFYTJcu7+lxmxBKSXAM+34g QBa2rhg9FbBEQ== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Oleg Nesterov , Paulo Andrade , "Peter Zijlstra (Intel)" , Sasha Levin Subject: [PATCH 6.19 619/844] x86/uprobes: Fix XOL allocation failure for 32-bit tasks Date: Sat, 28 Feb 2026 12:28:52 -0500 Message-ID: <20260228173244.1509663-620-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260228173244.1509663-1-sashal@kernel.org> References: <20260228173244.1509663-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit 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: Sasha Levin --- 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 7be8e361ca55b..619dddf54424e 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) return false; } + +#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 ee3d36eda45dd..f548fea2adec8 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 d546d32390a81..1ab7a7e4efb63 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; -- 2.51.0