From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f52.google.com (mail-wm1-f52.google.com [209.85.128.52]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7FF374FB9DF for ; Mon, 7 Sep 2026 16:52:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.52 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788799977; cv=none; b=s479broMehzkNjS8SUE8NHAoVRHGUsxuiBhWP0GnZEB3ZPi2laCQX7dFY1Spdy1PQDuuNdM7SMvcr4aBZrM9PhzYsPvwxtsIjQQ/lDaRNohdzAMEsYfDRjziUyDsQD6S9UgK7bVjpR47E1jeU0KTa6LD0sA51kjt2S+VDjoXzCo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788799977; c=relaxed/simple; bh=Q0tWSBlQLFk3oEvXn8y4hkhcwkljNZY80ooFvpI2RrA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SiHSIa7Lnwt5u0MEBi1goZE3nWvgmKxKZg3zHErhlxbeT0tPKM4rIobB798ApyPZhqbcnNmxaIBCu26zQLCxhsorpyTJxYTIDZM6x03VbZDJ2RjIEj7jrMAa//9AP/6fjumd3X7zuQwXJsOUoCH7GLp1Ylegg4nda4EG11M92hI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=U9dAsqCs; arc=none smtp.client-ip=209.85.128.52 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="U9dAsqCs" Received: by mail-wm1-f52.google.com with SMTP id 5b1f17b1804b1-49d0da752ffso16216025e9.3 for ; Mon, 07 Sep 2026 09:52:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1788799974; x=1789404774; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=aYJwxo5Nb9UiMMNksSdgP6g3PKaxvBMYGoOE/hW9Rkk=; b=U9dAsqCsC1Ng7j2pEbxxLUChmGYvpqUervfvREs7heCNRIOn9cu9aMRFNGKnSknHYh C2fzC0K9xb39/myBFYeRVx0hBDg5E8IxTeGv8un+Cfc+9Nehw7osc1sVHg5QZOdbPF47 yfSFYlde+XetyaAago/GAJPiihSea7kU1TF0Sizw2mw0kdeWHTMohDTkWjyqlPed9mm9 sWQqemLNx+AFhc1cNhBSKi6o5I1gjYYdoPQZEJMDKIAOYPenHBeIjyb9LB2YihTIWlAA QKT0rBPph+hU9wAV3xVc1MbGyc5PlG68LUcG2d0ob5Cmh3L36EmrkZOJCC6WZQIsjigb s8jw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1788799974; x=1789404774; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=aYJwxo5Nb9UiMMNksSdgP6g3PKaxvBMYGoOE/hW9Rkk=; b=R+ave+tVrzyhYHPYbXmuhNeKC8t6xiPZjmrc+JX6swMJOgzT+l3q2ojJxZkdQK0SX2 JNQD+zh/F5+kUsj4whhqWEq+vISwlck7OGXCPoktBcabEwLlvPq4WwLa2xVkN9lMRa3w pYBxEQ/7VAmKYZkFfjDP8vDklYsp7+Eeix8RVDzH/AM7OeLqEUkQpBvyJ9Ie/CRe0vWE erEwg01h7hiQQx84W9926QT/PNaRxWedmhMHCsYVREkYldQJd7FLjTPMDqe1dKjUzx9n FHOisMRtmwixpSjtpUNYDWmasMr3VE19K48zPFVKYMuPXAqlTXXvSAkd7DyAiZJUBJxA GjHg== X-Gm-Message-State: AFuF++kzspJCQmj7XznPZUwmWPMeHbBbmYWUEhe7odZC8iyGkELswsKs PVUZA+WL44y1uNPNk3o7TSIYOCMLPMwGa7RlBR9tZjc+n/uU0huKTRq5 X-Gm-Gg: AYBFou0xmW785/LMBbSqE3aBZMbSUMY0thpkz2Til7cHQevP36sg0PixO/Fwa3pnYFr p+XerDCcAAjIDBa34LRRmIAXuJ9wvN4qHCQqPdk9DkCVHFUY6/4p55wpivIoKPLMb1t9At1CRM3 8/OgGHIrvdaYvE1JhLtcblEtPtZZcqMJ8Vi1K6jw7LYHzLNx9Ghg1eIf7In8Ch8JOTahKZCZzIW 8H3nzJobv+KJesWqu0qnqMSEGJvlUcfsFMJDVv4HsfUxcAS0501zTCB53DLprhR+SDzIKd184S8 /5KvkaQHlNuRKB81pMRfBUCTJkQf4oMCCwX+sa28qvzKwmVV8JMsH0KeamtgXJCk5a4zISX19Rp atK1OF12ML0K11Rw5n8Z16nMa5AXPcg3Kp6WhW+SZOcjmjf0ex2rj3JnnwQUpGn41qsHYmMoZOC z3O03EVSBbL6YBB4LHbRQXHsDu6afDxSYPw706U9zUpii50KMnswAoOor+Rb0n/bR4CkN2BZRIW A== X-Received: by 2002:a05:600c:4fc9:b0:49c:fc6e:8cb9 with SMTP id 5b1f17b1804b1-49cfc6e8e1emr209497255e9.29.1788799973392; Mon, 07 Sep 2026 09:52:53 -0700 (PDT) Received: from dell-desktop ([2a02:587:4b5f:900:ef25:2f4:1792:4e6f]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49d03543064sm233022415e9.13.2026.09.07.09.52.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Sep 2026 09:52:52 -0700 (PDT) From: Anastasios Papagiannis To: bpf@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, david@kernel.org, akpm@linux-foundation.org, andrii@kernel.org, ast@kernel.org, brauner@kernel.org, daniel@iogearbox.net, eddyz87@gmail.com, kpsingh@kernel.org, ljs@kernel.org, matt@bobrowski.net, memxor@gmail.com, song@kernel.org, sun.jian.kdev@gmail.com, tasos.papagiannnis@gmail.com, utilityemal77@gmail.com, viro@zeniv.linux.org.uk Subject: [PATCH bpf-next v5 1/7] mm: Add copy_remote_mm_str() Date: Mon, 7 Sep 2026 19:52:14 +0300 Message-ID: <20260907165220.52431-2-tasos.papagiannnis@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260907165220.52431-1-tasos.papagiannnis@gmail.com> References: <20260907165220.52431-1-tasos.papagiannnis@gmail.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit copy_remote_vm_str() gets the target address space from a struct task_struct. This does not work for an address space that exists but is not yet associated with a task_struct, such as the mm held by struct linux_binprm during exec. Add copy_remote_mm_str(), which operates directly on a struct mm_struct. Use a common internal interface for the MMU and NOMMU implementations and define both public wrappers in mm/util.c. Preserve the existing copy_remote_vm_str() behavior, including handling zero-length requests before acquiring the task's mm. Signed-off-by: Anastasios Papagiannis --- include/linux/mm.h | 2 ++ mm/internal.h | 5 ++++ mm/memory.c | 41 ++---------------------------- mm/nommu.c | 41 ++---------------------------- mm/util.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++ 5 files changed, 73 insertions(+), 78 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index dd09c438fa23..d5bde1f71a97 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3326,6 +3326,8 @@ extern int access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf, int len, unsigned int gup_flags); #ifdef CONFIG_BPF_SYSCALL +extern int copy_remote_mm_str(struct mm_struct *mm, unsigned long addr, + void *buf, int len, unsigned int gup_flags); extern int copy_remote_vm_str(struct task_struct *tsk, unsigned long addr, void *buf, int len, unsigned int gup_flags); #endif diff --git a/mm/internal.h b/mm/internal.h index 38b1165212c9..8264a346d18a 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -25,6 +25,11 @@ struct folio_batch; struct hstate; +#ifdef CONFIG_BPF_SYSCALL +int __copy_remote_mm_str(struct mm_struct *mm, unsigned long addr, + void *buf, int len, unsigned int gup_flags); +#endif + struct huge_bootmem_page { struct list_head list; struct hstate *hstate; diff --git a/mm/memory.c b/mm/memory.c index 8b0c2c735d3d..fe2f5e988fb9 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -7331,8 +7331,8 @@ EXPORT_SYMBOL_GPL(access_process_vm); * Copy a string from another process's address space as given in mm. * If there is any error return -EFAULT. */ -static int __copy_remote_vm_str(struct mm_struct *mm, unsigned long addr, - void *buf, int len, unsigned int gup_flags) +int __copy_remote_mm_str(struct mm_struct *mm, unsigned long addr, + void *buf, int len, unsigned int gup_flags) { void *old_buf = buf; int err = 0; @@ -7407,43 +7407,6 @@ static int __copy_remote_vm_str(struct mm_struct *mm, unsigned long addr, return err; return buf - old_buf; } - -/** - * copy_remote_vm_str - copy a string from another process's address space. - * @tsk: the task of the target address space - * @addr: start address to read from - * @buf: destination buffer - * @len: number of bytes to copy - * @gup_flags: flags modifying lookup behaviour - * - * The caller must hold a reference on @mm. - * - * Return: number of bytes copied from @addr (source) to @buf (destination); - * not including the trailing NUL. Always guaranteed to leave NUL-terminated - * buffer. On any error, return -EFAULT. - */ -int copy_remote_vm_str(struct task_struct *tsk, unsigned long addr, - void *buf, int len, unsigned int gup_flags) -{ - struct mm_struct *mm; - int ret; - - if (unlikely(len == 0)) - return 0; - - mm = get_task_mm(tsk); - if (!mm) { - *(char *)buf = '\0'; - return -EFAULT; - } - - ret = __copy_remote_vm_str(mm, addr, buf, len, gup_flags); - - mmput(mm); - - return ret; -} -EXPORT_SYMBOL_GPL(copy_remote_vm_str); #endif /* CONFIG_BPF_SYSCALL */ /* diff --git a/mm/nommu.c b/mm/nommu.c index 498e01ee40b0..98596e60311f 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -1746,8 +1746,8 @@ EXPORT_SYMBOL_GPL(access_process_vm); * Copy a string from another process's address space as given in mm. * If there is any error return -EFAULT. */ -static int __copy_remote_vm_str(struct mm_struct *mm, unsigned long addr, - void *buf, int len) +int __copy_remote_mm_str(struct mm_struct *mm, unsigned long addr, + void *buf, int len, unsigned int gup_flags) { unsigned long addr_end; struct vm_area_struct *vma; @@ -1781,43 +1781,6 @@ static int __copy_remote_vm_str(struct mm_struct *mm, unsigned long addr, mmap_read_unlock(mm); return ret; } - -/** - * copy_remote_vm_str - copy a string from another process's address space. - * @tsk: the task of the target address space - * @addr: start address to read from - * @buf: destination buffer - * @len: number of bytes to copy - * @gup_flags: flags modifying lookup behaviour (unused) - * - * The caller must hold a reference on @mm. - * - * Return: number of bytes copied from @addr (source) to @buf (destination); - * not including the trailing NUL. Always guaranteed to leave NUL-terminated - * buffer. On any error, return -EFAULT. - */ -int copy_remote_vm_str(struct task_struct *tsk, unsigned long addr, - void *buf, int len, unsigned int gup_flags) -{ - struct mm_struct *mm; - int ret; - - if (unlikely(len == 0)) - return 0; - - mm = get_task_mm(tsk); - if (!mm) { - *(char *)buf = '\0'; - return -EFAULT; - } - - ret = __copy_remote_vm_str(mm, addr, buf, len); - - mmput(mm); - - return ret; -} -EXPORT_SYMBOL_GPL(copy_remote_vm_str); #endif /* CONFIG_BPF_SYSCALL */ /** diff --git a/mm/util.c b/mm/util.c index bf0513d1d3d0..2eca27b02791 100644 --- a/mm/util.c +++ b/mm/util.c @@ -1061,6 +1061,68 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen) return res; } +#ifdef CONFIG_BPF_SYSCALL +/** + * copy_remote_mm_str - copy a string from a remote address space. + * @mm: the remote address space + * @addr: start address to read from + * @buf: destination buffer + * @len: number of bytes to copy + * @gup_flags: flags modifying lookup behaviour + * + * The caller must hold a reference on @mm. + * + * Return: number of bytes copied from @addr (source) to @buf (destination), + * not including the trailing NUL. If @len is zero, return 0 without accessing + * @buf. Otherwise, @buf is always NUL-terminated. On any error, return + * -EFAULT. + */ +int copy_remote_mm_str(struct mm_struct *mm, unsigned long addr, + void *buf, int len, unsigned int gup_flags) +{ + if (unlikely(len == 0)) + return 0; + + return __copy_remote_mm_str(mm, addr, buf, len, gup_flags); +} + +/** + * copy_remote_vm_str - copy a string from another process's address space. + * @tsk: the task of the target address space + * @addr: start address to read from + * @buf: destination buffer + * @len: number of bytes to copy + * @gup_flags: flags modifying lookup behaviour + * + * Return: number of bytes copied from @addr (source) to @buf (destination), + * not including the trailing NUL. If @len is zero, return 0 without accessing + * @buf. Otherwise, @buf is always NUL-terminated. On any error, return + * -EFAULT. + */ +int copy_remote_vm_str(struct task_struct *tsk, unsigned long addr, + void *buf, int len, unsigned int gup_flags) +{ + struct mm_struct *mm; + int ret; + + if (unlikely(len == 0)) + return 0; + + mm = get_task_mm(tsk); + if (!mm) { + *(char *)buf = '\0'; + return -EFAULT; + } + + ret = __copy_remote_mm_str(mm, addr, buf, len, gup_flags); + + mmput(mm); + + return ret; +} +EXPORT_SYMBOL_GPL(copy_remote_vm_str); +#endif /* CONFIG_BPF_SYSCALL */ + int __weak memcmp_pages(struct page *page1, struct page *page2) { char *addr1, *addr2; -- 2.55.0