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From: "Ahmed S. Darwish" <darwish.07@gmail.com>
To: Alexey Dobriyan <adobriyan@gmail.com>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 11/13] proc: readdir /proc/*/task
Date: Tue, 28 Aug 2018 12:36:22 +0000
Message-ID: <20180828123622.GA2087@darwi-kernel> (raw)
In-Reply-To: <20180827231503.26899-11-adobriyan@gmail.com>

On Tue, Aug 28, 2018 at 02:15:01AM +0300, Alexey Dobriyan wrote:
> ---
>  fs/proc/base.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>

Missing description and S-o-b. Further comments below..

> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 33f444721965..668e465c86b3 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -3549,11 +3549,11 @@ static int proc_task_readdir(struct file *file, struct dir_context *ctx)
>  	for (task = first_tid(proc_pid(inode), tid, ctx->pos - 2, ns);
>  	     task;
>  	     task = next_tid(task), ctx->pos++) {
> -		char name[10 + 1];
> -		unsigned int len;
> +		char name[10], *p = name + sizeof(name);
> +

Multiple issues:

- len should be 11, as was in the original code
  (0xffffffff = 4294967295, 10 letters)

- while we're at it, let's use a constant for the '11' instead of
  mysterious magic numbers

- 'p' is clearly overflowing the stack here

>  		tid = task_pid_nr_ns(task, ns);
> -		len = snprintf(name, sizeof(name), "%u", tid);
> -		if (!proc_fill_cache(file, ctx, name, len,
> +		p = _print_integer_u32(p, tid);
> +		if (!proc_fill_cache(file, ctx, p, name + sizeof(name) - p,

You're replacing snprintf() code __that did proper len checking__
with code that does not. That's not good.

I can't see how the fourth proc_fill_cache() parameter, ``name +
sizeof(name)'' safely ever replace the original 'len' parameter.
It's a pointer value .. (!)

Overall this looks like a broken patch submitted by mistake.

Thanks,

-- 
Darwish
http://darwish.chasingpointers.com

  reply index

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-27 23:14 [PATCH 01/13] seq_file: rewrite seq_puts() in terms of seq_write() Alexey Dobriyan
2018-08-27 23:14 ` [PATCH 02/13] proc: apply seq_puts() whenever possible Alexey Dobriyan
2018-08-27 23:14 ` [PATCH 03/13] proc: rename "p" variable in proc_readfd_common() Alexey Dobriyan
2018-08-27 23:14 ` [PATCH 04/13] proc: rename "p" variable in proc_map_files_readdir() Alexey Dobriyan
2018-08-27 23:14 ` [PATCH 05/13] proc: new and improved way to print decimals Alexey Dobriyan
2018-08-27 23:14 ` [PATCH 06/13] proc: convert /proc/self to _print_integer() Alexey Dobriyan
2018-08-29  9:50   ` David Laight
2018-08-30 13:13     ` Alexey Dobriyan
2018-08-27 23:14 ` [PATCH 07/13] proc: convert /proc/thread-self " Alexey Dobriyan
2018-08-27 23:14 ` [PATCH 08/13] proc: convert /proc/*/fd " Alexey Dobriyan
2018-08-27 23:14 ` [PATCH 09/13] proc: convert dentry flushing on exit " Alexey Dobriyan
2018-08-27 23:15 ` [PATCH 10/13] proc: convert readdir /proc " Alexey Dobriyan
2018-08-27 23:15 ` [PATCH 11/13] proc: readdir /proc/*/task Alexey Dobriyan
2018-08-28 12:36   ` Ahmed S. Darwish [this message]
2018-08-28 13:04     ` Ahmed S. Darwish
2018-08-28 19:35       ` Alexey Dobriyan
2018-08-29 23:43         ` Andrew Morton
2018-08-30 13:20           ` Alexey Dobriyan
2018-08-28 19:31     ` Alexey Dobriyan
2018-08-27 23:15 ` [PATCH 12/13] proc: convert /proc/*/statm to _print_integer() Alexey Dobriyan
2018-08-27 23:15 ` [PATCH 13/13] proc: convert /proc/*/task/*/children " Alexey Dobriyan
2018-08-28 18:24 ` [PATCH 01/13] seq_file: rewrite seq_puts() in terms of seq_write() Joe Perches
2018-08-28 20:48   ` Joe Perches
2018-09-03 14:17 ` Alexey Dobriyan

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