From patchwork Tue Jan 7 02:06:31 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jordan Rome X-Patchwork-Id: 13927968 X-Patchwork-Delegate: bpf@iogearbox.net Received: from mout.perfora.net (mout.perfora.net [74.208.4.194]) (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 29657ECC for ; Tue, 7 Jan 2025 02:12:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.208.4.194 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736215958; cv=none; b=VyUx9aCibEUOl/y38pNJDcIxlFBzO6Xivz/xcpP3vGCH1TtrWxLCTcvcbmaSxnXp+QR/MFHjoTxynQaixuHqdvOr0l9/aYwlMaWv+JB+4IwMcwkfO/t/ynFFFk8HQtEUDxJGZ6cjiDBwtO0a0kxQdRaOpGxGFm3kFMd9iUT808A= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736215958; c=relaxed/simple; bh=/J5L2tYmebI1qwyWCtAD5UhOp6Si8cKLLRLy/rh40So=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=MGZYB8xJvCaTew3yKBi5PZvLKBPLlUJ/PnEIsn8rRjEIMG0/8ZC/sKTaXmjIZCEF8Y8322Q7vp2ShZnwHZZrEsO+lSDdcP4XmIl5a01nBnVCU6lPm6EtjvWaEzOyPiSeaISH9kEB1od3Pd3C1NR51z/ZUznCIzUsz6+9e7hAtjg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=jordanrome.com; spf=pass smtp.mailfrom=jordanrome.com; dkim=pass (2048-bit key) header.d=jordanrome.com header.i=linux@jordanrome.com header.b=2qOQiykY; arc=none smtp.client-ip=74.208.4.194 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=jordanrome.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=jordanrome.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=jordanrome.com header.i=linux@jordanrome.com header.b="2qOQiykY" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=jordanrome.com; s=s1-ionos; t=1736215950; x=1736820750; i=linux@jordanrome.com; bh=3ePT0FPt9l0Qzkz0xRTw2LrsfjW4Z5KL+i91TUZCoiY=; h=X-UI-Sender-Class:From:To:Cc:Subject:Date:Message-ID: MIME-Version:Content-Transfer-Encoding:cc: content-transfer-encoding:content-type:date:from:message-id: mime-version:reply-to:subject:to; b=2qOQiykYOK/Jmr6CODErS5q1lgZ2BGDH5qHzgsxjvbvZq7yp6tR8ZFqrwgIS9oQ9 GYpIiDmZRStodc6t5G56w4lbofX8nyIoYgn0ZFVUk9BylaDYuApLMVe8klMY75WtI ZqqtHhsel8Ok/+HtnNba2UZkTCS/9VblUcSkGQCSETXC49atfShnDYRC00hKpMkUR FJwDW9gMHgJN0R1LBAqfnbA0z7rYBPuG94L6yIljVOHDyunHW+MXWkwnHpdaU6pKu a5RPlCYWsvHpTdsV//usq2k2Nl0Ks+orwiuBexLcIDW4W1zeklqekuPo8RCCsQBRY brYJxR5WlquH6zWLHA== X-UI-Sender-Class: 55c96926-9e95-11ee-ae09-1f7a4046a0f6 Received: from localhost ([69.171.251.13]) by mrelay.perfora.net (mreueus002 [74.208.5.2]) with ESMTPSA (Nemesis) id 0MHIlZ-1tIfAm04jz-008nC5; Tue, 07 Jan 2025 03:06:43 +0100 From: Jordan Rome To: bpf@vger.kernel.org Cc: linux-mm@kvack.org, Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Kernel Team , Andrew Morton , Shakeel Butt Subject: [bpf-next v2 1/2] bpf: Add bpf_copy_from_user_task_str kfunc Date: Mon, 6 Jan 2025 18:06:31 -0800 Message-ID: <20250107020632.170883-1-linux@jordanrome.com> X-Mailer: git-send-email 2.43.5 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Provags-ID: V03:K1:swEFtqhmW2Kwgld9kRCHV/0VrQFU6PZ5hV+JiC+7/AR7So7t/EL C/GGahB7cSR1JDBXJ1k2Sly455EiX0+T86stg8IH1wt13fcvppXhcq4p6tpO/wZJJXe7MkF R0q7AODVholSw2csXtbuLreZYLgF4miBagbv28HnOespwAyVXT4VqctkPEedZZDqRavoAxS WrZFxxHGQnYM3yAeOZDPg== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:/v3exhYE17k=;B+un3PO91ndLDTqzVXAK/Iiv3Wa XZsP9AHT7ttsJnHGahqrXO/6eP6Y4pofhvFCWwgQYDuVe3cNA7Gi9KZw6MxLNMh1BAMs+g12c v3Xwp3AQvtGh8EMQcXbK/QQBIHHBlW5KhdVeWMyyZISAAjU8sU4jiPHbMm2guK2hLAL46S6NU OxfTCUBxabNGtS/dGuLsvOn+21uXS2Vm9ern6iFQcJevb5TjtyBT7e4mPpVKRVHGqHpSkcZuq mqI7mctB/13VcdWIUR+4ewyZU5q+FrBXtmS6EV2otjGXqs2dKd3cVWShJiBIvesyHlwoBnEJF iNdC1IllWyNvemzFGRV0KUykQUpA6AauRjQ3EWWFqHSkyMpwovKMCUPbwT6mVTOqcWwqasPYj MOYsV40XlJOE6+X97Rl+Te1QuXi+zuBWkWusy6ebJKNyUs76RLufaLjGX8D0jMs78OCX2OFeu Bwr+Awnd0U/21QLKV/QJrMJM1awDoRdZxxduEm7gEGXzxPQ72qhYqt7zy2WNh11RPMJE4Ep9o BsD4UutbJf6S50wHN/m7/fT6bYUsJh3+DqONNqHqL3H9jWlo2vX7yHJ68oem2MeB8yj7digVP QVcmCcISxPpmP2pwKnQltIHh/WoZ23XucSPj9Fr9YZfF6p4z388DQkPrH6fNn5erq2h4RnFvp kApsSh9+2t/91Aj6uTg1Grdk1NV5R6Ci7XYJyHG/n5vxDACgMw98eF9zJ1PVAknx7j4CVvJNV 7DAjfusEXUDDuppcu0wyxbU4p28tynsew4spPa0w9sSAPAHHyv9Bq9b+a5IPPfe8TtLzBSI42 XRjWpkZ/71FbN2miKwM3ZdG5Zhtz+3eeB1cb8hUhk4jPcVpc5KIQT2npAB5ggJeWuOVX+GNxF cTGg8ExWSHgviyPQoeuOg/eAY2nLCv6ymhFw3AD0xrrS1LMf5OLQfj+nULXOrrFIXhegUImnu M7QaHwGcy3Jr7WIvEl9vxXhwTSv+K+1+owmKgDoFj+ju+o19uDdkeVzswj58mlm0gTc9U2d6c LcG734Q9pA2l9I7zkeovE02BYHwnamo/W3PBAqm X-Patchwork-Delegate: bpf@iogearbox.net This new kfunc will be able to copy a string from another process's/task's address space. This is similar to `bpf_copy_from_user_str` but accepts a `struct task_struct*` argument. This required adding an additional function in memory.c, namely `copy_str_from_process_vm`, which works similar to `access_process_vm` but utilizes the `strncpy_from_user` helper and only supports reading/copying and not writing. Signed-off-by: Jordan Rome --- include/linux/mm.h | 3 ++ kernel/bpf/helpers.c | 46 ++++++++++++++++++++ mm/memory.c | 101 +++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 150 insertions(+) -- 2.43.5 diff --git a/include/linux/mm.h b/include/linux/mm.h index c39c4945946c..52b304b20630 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2484,6 +2484,9 @@ extern int access_process_vm(struct task_struct *tsk, unsigned long addr, extern int access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf, int len, unsigned int gup_flags); +extern int copy_str_from_process_vm(struct task_struct *tsk, unsigned long addr, + void *buf, int len, unsigned int gup_flags); + long get_user_pages_remote(struct mm_struct *mm, unsigned long start, unsigned long nr_pages, unsigned int gup_flags, struct page **pages, diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index cd5f9884d85b..45d41b7a9906 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -3072,6 +3072,51 @@ __bpf_kfunc void bpf_local_irq_restore(unsigned long *flags__irq_flag) local_irq_restore(*flags__irq_flag); } +/** + * bpf_copy_from_user_task_str() - Copy a string from an task's address space + * @dst: Destination address, in kernel space. This buffer must be + * at least @dst__sz bytes long. + * @dst__sz: Maximum number of bytes to copy, includes the trailing NUL. + * @unsafe_ptr__ign: Source address in the task's address space. + * @tsk: The task whose address space will be used + * @flags: The only supported flag is BPF_F_PAD_ZEROS + * + * Copies a NULL-terminated string from a task's address space to BPF space. + * If user string is too long this will still ensure zero termination in the + * dst buffer unless buffer size is 0. + * + * If BPF_F_PAD_ZEROS flag is set, memset the tail of @dst to 0 on success and + * memset all of @dst on failure. + */ +__bpf_kfunc int bpf_copy_from_user_task_str(void *dst, u32 dst__sz, const void __user *unsafe_ptr__ign, struct task_struct *tsk, u64 flags) +{ + int count = dst__sz - 1; + int ret = 0; + + if (unlikely(flags & ~BPF_F_PAD_ZEROS)) + return -EINVAL; + + if (unlikely(!dst__sz)) + return 0; + + ret = copy_str_from_process_vm(tsk, (unsigned long)unsafe_ptr__ign, dst, count, 0); + + if (ret <= 0) { + if (flags & BPF_F_PAD_ZEROS) + memset((char *)dst, 0, dst__sz); + return ret; + } + + if (ret < count) { + if (flags & BPF_F_PAD_ZEROS) + memset((char *)dst + ret, 0, dst__sz - ret); + } else { + ((char *)dst)[count] = '\0'; + } + + return ret + 1; +} + __bpf_kfunc_end_defs(); BTF_KFUNCS_START(generic_btf_ids) @@ -3164,6 +3209,7 @@ BTF_ID_FLAGS(func, bpf_iter_bits_new, KF_ITER_NEW) BTF_ID_FLAGS(func, bpf_iter_bits_next, KF_ITER_NEXT | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_iter_bits_destroy, KF_ITER_DESTROY) BTF_ID_FLAGS(func, bpf_copy_from_user_str, KF_SLEEPABLE) +BTF_ID_FLAGS(func, bpf_copy_from_user_task_str, KF_SLEEPABLE) BTF_ID_FLAGS(func, bpf_get_kmem_cache) BTF_ID_FLAGS(func, bpf_iter_kmem_cache_new, KF_ITER_NEW | KF_SLEEPABLE) BTF_ID_FLAGS(func, bpf_iter_kmem_cache_next, KF_ITER_NEXT | KF_RET_NULL | KF_SLEEPABLE) diff --git a/mm/memory.c b/mm/memory.c index 75c2dfd04f72..514490bd7d6d 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -6673,6 +6673,75 @@ static int __access_remote_vm(struct mm_struct *mm, unsigned long addr, return buf - old_buf; } +/* + * Copy a string from another process's address space as given in mm. + * Don't return partial results. If there is any error return -EFAULT. + */ +static int __copy_str_from_remote_vm(struct mm_struct *mm, unsigned long addr, + void *buf, int len, unsigned int gup_flags) +{ + void *old_buf = buf; + int err = 0; + + if (mmap_read_lock_killable(mm)) + return -EFAULT; + + /* Untag the address before looking up the VMA */ + addr = untagged_addr_remote(mm, addr); + + /* Avoid triggering the temporary warning in __get_user_pages */ + if (!vma_lookup(mm, addr)) { + mmap_read_unlock(mm); + return -EFAULT; + } + + while (len) { + int bytes, offset, retval; + void *maddr; + struct vm_area_struct *vma = NULL; + struct page *page = get_user_page_vma_remote(mm, addr, + gup_flags, &vma); + + if (IS_ERR(page)) { + /* + * Treat as a total failure for now until we decide how + * to handle the CONFIG_HAVE_IOREMAP_PROT case and + * stack expansion. + */ + err = -EFAULT; + break; + } + + bytes = len; + offset = addr & (PAGE_SIZE - 1); + if (bytes > PAGE_SIZE - offset) + bytes = PAGE_SIZE - offset; + + maddr = kmap_local_page(page); + retval = strncpy_from_user(buf, (const char __user *)addr, bytes); + unmap_and_put_page(page, maddr); + + if (retval < 0) { + err = retval; + break; + } + + len -= retval; + buf += retval; + addr += retval; + + /* Found the end of the string */ + if (retval < bytes) + break; + } + mmap_read_unlock(mm); + + if (err) + return err; + + return buf - old_buf; +} + /** * access_remote_vm - access another process' address space * @mm: the mm_struct of the target address space @@ -6714,6 +6783,38 @@ int access_process_vm(struct task_struct *tsk, unsigned long addr, } EXPORT_SYMBOL_GPL(access_process_vm); +/** + * copy_str_from_process_vm - copy a string from another process's address space. + * @tsk: the task of the target address space + * @addr: start address to access + * @buf: source or destination buffer + * @len: number of bytes to transfer + * @gup_flags: flags modifying lookup behaviour + * + * The caller must hold a reference on @mm. + * + * Return: number of bytes copied from source to destination. If the string + * is shorter than @len then return the length of the string. + * On any error, return -EFAULT. + */ +int copy_str_from_process_vm(struct task_struct *tsk, unsigned long addr, + void *buf, int len, unsigned int gup_flags) +{ + struct mm_struct *mm; + int ret; + + mm = get_task_mm(tsk); + if (!mm) + return -EFAULT; + + ret = __copy_str_from_remote_vm(mm, addr, buf, len, gup_flags); + + mmput(mm); + + return ret; +} +EXPORT_SYMBOL_GPL(copy_str_from_process_vm); + /* * Print the name of a VMA. */