From: Matthew Wilcox <willy@infradead.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Kees Cook <keescook@chromium.org>,
Iurii Zaikin <yzaikin@google.com>,
Luis Chamberlain <mcgrof@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
linux-fsdevel@vger.kernel.org, netdev@vger.kernel.org,
bpf@vger.kernel.org
Subject: Re: [PATCH 6/6] sysctl: pass kernel pointers to ->proc_handler
Date: Fri, 17 Apr 2020 11:17:18 -0700 [thread overview]
Message-ID: <20200417181718.GN5820@bombadil.infradead.org> (raw)
In-Reply-To: <20200417064146.1086644-7-hch@lst.de>
On Fri, Apr 17, 2020 at 08:41:46AM +0200, Christoph Hellwig wrote:
> diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
> index b6f5d459b087..d5c9a9bf4e90 100644
> --- a/fs/proc/proc_sysctl.c
> +++ b/fs/proc/proc_sysctl.c
> @@ -539,13 +539,13 @@ static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
> return err;
> }
>
> -static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf,
> +static ssize_t proc_sys_call_handler(struct file *filp, void __user *ubuf,
> size_t count, loff_t *ppos, int write)
> {
> struct inode *inode = file_inode(filp);
> struct ctl_table_header *head = grab_header(inode);
> struct ctl_table *table = PROC_I(inode)->sysctl_entry;
> - void *new_buf = NULL;
> + void *kbuf;
> ssize_t error;
>
> if (IS_ERR(head))
> @@ -564,27 +564,36 @@ static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf,
> if (!table->proc_handler)
> goto out;
>
> - error = BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, buf, &count,
> - ppos, &new_buf);
> + if (write) {
> + kbuf = memdup_user_nul(ubuf, count);
> + if (IS_ERR(kbuf)) {
> + error = PTR_ERR(kbuf);
> + goto out;
> + }
> + } else {
> + error = -ENOMEM;
> + kbuf = kzalloc(count, GFP_KERNEL);
> + if (!kbuf)
> + goto out;
> + }
> +
> + error = BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, &kbuf, &count,
> + ppos);
> if (error)
> - goto out;
> + goto out_free_buf;
>
> /* careful: calling conventions are nasty here */
I think this comment can go now ;-)
> - if (new_buf) {
> - mm_segment_t old_fs;
> -
> - old_fs = get_fs();
> - set_fs(KERNEL_DS);
> - error = table->proc_handler(table, write, (void __user *)new_buf,
> - &count, ppos);
> - set_fs(old_fs);
> - kfree(new_buf);
> - } else {
> - error = table->proc_handler(table, write, buf, &count, ppos);
> - }
> + error = table->proc_handler(table, write, kbuf, &count, ppos);
> + if (error)
> + goto out_free_buf;
> +
> + error = -EFAULT;
> + if (copy_to_user(ubuf, kbuf, count))
> + goto out_free_buf;
Can we skip this if !write? Indeed, don't we have to in case the user has
passed a pointer to a read-only memory page?
next prev parent reply other threads:[~2020-04-17 18:17 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-17 6:41 pass kernel pointers to the sysctl ->proc_handler method Christoph Hellwig
2020-04-17 6:41 ` [PATCH 1/6] bpf-cgroup: remove unused exports Christoph Hellwig
2020-04-17 6:41 ` [PATCH 2/6] firmware_loader: " Christoph Hellwig
2020-04-17 7:43 ` Greg Kroah-Hartman
2020-04-17 7:48 ` Christoph Hellwig
2020-04-17 6:41 ` [PATCH 3/6] mm: remove watermark_boost_factor_sysctl_handler Christoph Hellwig
2020-04-17 6:41 ` [PATCH 4/6] sysctl: remove all extern declaration from sysctl.c Christoph Hellwig
2020-04-22 12:33 ` Eric W. Biederman
2020-04-22 17:26 ` Christoph Hellwig
2020-04-17 6:41 ` [PATCH 5/6] sysctl: avoid forward declarations Christoph Hellwig
2020-04-17 6:41 ` [PATCH 6/6] sysctl: pass kernel pointers to ->proc_handler Christoph Hellwig
2020-04-17 7:45 ` Greg Kroah-Hartman
2020-04-17 18:17 ` Matthew Wilcox [this message]
2020-04-21 7:42 ` Christoph Hellwig
2020-04-17 19:39 ` Andrey Ignatov
2020-04-17 19:50 ` Matthew Wilcox
2020-04-17 22:38 ` Andrey Ignatov
2020-04-21 7:55 ` Christoph Hellwig
2020-04-17 22:36 ` [Potential Spoof] " Andrey Ignatov
2020-04-17 18:00 ` pass kernel pointers to the sysctl ->proc_handler method Luis Chamberlain
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