Subject: Re: [net-next PATCH v5 2/3] sysctl: add proc_do_large_bitmap

From: Cong Wang <[email-masked]>
Date: Wed, 24 Feb 2010 13:24:00 +0800

Octavian Purdila wrote:
> 
> Here is a new version of this patch which fixes both the comma and invalid 
> value issues, please give it a try.
> 

Sorry, it is even worse. :(

> [net-next PATCH v5 2/3] sysctl: add proc_do_large_bitmap
> 
> The new function can be used to read/write large bitmaps via /proc. A
> comma separated range format is used for compact output and input
> (e.g. 1,3-4,10-10).
> 

Writing "50000-50100" gets EINVAL, it should be success.
Writing "50000,50100" fails too.

Please, at least, do some basic testing.

Also some comments below.

> Writing into the file will first reset the bitmap then update it
> based on the given input.
> 
> Signed-off-by: Octavian Purdila <[email-masked]>
> Cc: WANG Cong <[email-masked]>
> Cc: Eric W. Biederman <[email-masked]>

Please resend the whole patchset, and update the doc in patch 3/3.

> ---
>  include/linux/sysctl.h |    2 +
>  kernel/sysctl.c        |  134 
> ++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 136 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
> index f66014c..7bb5cb6 100644
> --- a/include/linux/sysctl.h
> +++ b/include/linux/sysctl.h
> @@ -980,6 +980,8 @@ extern int proc_doulongvec_minmax(struct ctl_table *, int,
>  				  void __user *, size_t *, loff_t *);
>  extern int proc_doulongvec_ms_jiffies_minmax(struct ctl_table *table, int,
>  				      void __user *, size_t *, loff_t *);
> +extern int proc_do_large_bitmap(struct ctl_table *, int,
> +				void __user *, size_t *, loff_t *);
>  
>  /*
>   * Register a set of sysctl names by calling register_sysctl_table
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 5259727..d8ea839 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -2635,6 +2635,140 @@ static int proc_do_cad_pid(struct ctl_table *table, 
> int write,

The above line is wrong, it should be a part of previous line.

>  	return 0;
>  }
>  
> +/**
> + * proc_do_large_bitmap - read/write from/to a large bitmap
> + * @table: the sysctl table
> + * @write: %TRUE if this is a write to the sysctl file
> + * @buffer: the user buffer
> + * @lenp: the size of the user buffer
> + * @ppos: file position
> + *
> + * The bitmap is stored at table->data and the bitmap length (in bits)
> + * in table->maxlen.
> + *
> + * We use a range comma separated format (e.g. 1,3-4,10-10) so that
> + * large bitmaps may be represented in a compact manner. Writing into
> + * the file will clear the bitmap then update it with the given input.
> + *
> + * Returns 0 on success.
> + */
> +int proc_do_large_bitmap(struct ctl_table *table, int write,
> +			 void __user *_buffer, size_t *lenp, loff_t *ppos)
> +{
> +	bool first = 1;
> +	unsigned long *bitmap = (unsigned long *) table->data;
> +	unsigned long bitmap_len = table->maxlen;
> +	int left = *lenp, err = 0;

'left' should be size_t.

> +	char __user *buffer = (char __user *) _buffer;
> +	char tr_a[] = { '-', ',', 0 }, tr_b[] = { ',', 0 }, c;
> +
> +
> +	if (!bitmap_len || !left || (*ppos && !write)) {
> +		*lenp = 0;
> +		return 0;
> +	}
> +
> +	if (write) {
> +		err = proc_skip_wspace(&buffer, &left);
> +		while (!err && left) {
> +			unsigned long val_a, val_b;
> +			bool neg;
> +
> +			err = proc_get_ulong(&buffer, &left, tr_a,
> +					     &val_a, &neg, &c);
> +			if (err)
> +				break;
> +
> +			if (val_a >= bitmap_len || neg) {
> +				err = -EINVAL;
> +				break;
> +			}
> +
> +			val_b = val_a;
> +			if (left && c == '-') {
> +				/* skip the - */
> +				buffer++; left--;
> +
> +				err = proc_get_ulong(&buffer, &left, tr_b,
> +						     &val_b, &neg, &c);
> +				if (err)
> +					break;
> +
> +				if (val_b >= bitmap_len || neg ||
> +				    val_a > val_b) {
> +					err = -EINVAL;
> +					break;
> +				}
> +			}
> +
> +			if (left) {
> +				err = proc_skip_wspace(&buffer, &left);
> +				if (err)
> +					break;
> +				if (left) {
> +					if (get_user(c, buffer)) {
> +						err = -EFAULT;
> +						break;
> +					}
> +					if (c != ',') {
> +						err = -EINVAL;
> +						break;
> +					}
> +					/* skip the , */
> +					buffer++; left--;
> +				}
> +			}
> +
> +			if (first)
> +				bitmap_clear(bitmap, 0, bitmap_len);
> +
> +			while (val_a <= val_b)
> +				set_bit(val_a++, bitmap);
> +
> +			first = 0;
> +		}
> +		if (!err)
> +			err = proc_skip_wspace(&buffer, &left);
> +	} else {
> +		unsigned long bit_a, bit_b = 0;
> +
> +		while (left) {
> +			bit_a = find_next_bit(bitmap, bitmap_len, bit_b);
> +			if (bit_a >= bitmap_len)
> +				break;
> +			bit_b = find_next_zero_bit(bitmap, bitmap_len,
> +						   bit_a + 1) - 1;
> +
> +			err = proc_put_ulong(&buffer, &left, bit_a, 0, first,
> +					     ',');
> +			if (err)
> +				break;
> +			if (bit_a != bit_b) {
> +				err = proc_put_char(&buffer, &left, '-');
> +				if (err)
> +					break;
> +				err = proc_put_ulong(&buffer, &left, bit_b, 0,
> +						     1, 0);
> +				if (err)
> +					break;
> +			}
> +
> +			first = 0; bit_b++;
> +		}
> +		if (!err)
> +			err = proc_put_char(&buffer, &left, '\n');
> +	}
> +
> +	if (first) {
> +		if (err)
> +			return err;
> +		bitmap_clear(bitmap, 0, bitmap_len);
> +	}
> +	*lenp -= left;
> +	*ppos += *lenp;
> +	return 0;
> +}
> +
>  #else /* CONFIG_PROC_FS */
>  
>  int proc_dostring(struct ctl_table *table, int write,