linux-hardening - Re: [PATCH 1/1] trace: Move readpos from seq_buf to trace

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Message-ID: <20231019180904.70e623f1@gandalf.local.home>
Date: Thu, 19 Oct 2023 18:09:04 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: kernel test robot <lkp@...el.com>
Cc: "Matthew Wilcox (Oracle)" <willy@...radead.org>,
 oe-kbuild-all@...ts.linux.dev, Kees Cook <keescook@...omium.org>, Christoph
 Hellwig <hch@....de>, Justin Stitt <justinstitt@...gle.com>,
 linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org, Kent
 Overstreet <kmo@...erainc.com>, Petr Mladek <pmladek@...e.com>, Andy
 Shevchenko <andriy.shevchenko@...ux.intel.com>, Rasmus Villemoes
 <linux@...musvillemoes.dk>, Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: Re: [PATCH 1/1] trace: Move readpos from seq_buf to trace_seq

On Fri, 20 Oct 2023 05:59:36 +0800
kernel test robot <lkp@...el.com> wrote:

> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25  323) /**
> 9dbbc3b9d09d6d lib/seq_buf.c          Zhen Lei                 2021-07-07  324   * seq_buf_to_user - copy the sequence buffer to user space
> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25  325)  * @s: seq_buf descriptor
> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25  326)  * @ubuf: The userspace memory location to copy to
> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25  327)  * @cnt: The amount to copy

When you resend, I guess you should add the @start as well.

-- Steve

> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25  328)  *
> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25  329)  * Copies the sequence buffer into the userspace memory pointed to
> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25  330)  * by @ubuf. It starts from the last read position (@s->readpos)
> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25  331)  * and writes up to @cnt characters or till it reaches the end of
> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25  332)  * the content in the buffer (@s->len), which ever comes first.
> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25  333)  *
> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25  334)  * On success, it returns a positive number of the number of bytes
> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25  335)  * it copied.
> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25  336)  *
> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25  337)  * On failure it returns -EBUSY if all of the content in the
> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25  338)  * sequence has been already read, which includes nothing in the
> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25  339)  * sequence (@s->len == @s->readpos).
> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25  340)  *
> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25  341)  * Returns -EFAULT if the copy to userspace fails.
> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25  342)  */
> 9377093a882be0 lib/seq_buf.c          Matthew Wilcox (Oracle   2023-10-19  343) int seq_buf_to_user(struct seq_buf *s, char __user *ubuf, size_t start, int cnt)
> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25 @344) {
> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25  345) 	int len;
> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25  346) 	int ret;
> 3a161d99c43ce7 kernel/trace/seq_buf.c Steven Rostedt (Red Hat  2014-06-25  347)