Re: [keyutils PATCH v2] man: keyctl_read(3): fix documentation for short buffer case

[Eric Biggers <ebiggers3@gmail.com>]

On Thu, Nov 02, 2017 at 11:06:05AM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> When keyctl_read() is passed a buffer that is too small, the behavior is
> inconsistent.  Some key types will fill as much of the buffer as
> possible, while others won't copy anything.  Moreover, the in-kernel
> documentation contradicted the man page on this point.
> 
> Update the man page to say that this point is unspecified.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  man/keyctl_read.3 | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/man/keyctl_read.3 b/man/keyctl_read.3
> index 25821ad..852bc05 100644
> --- a/man/keyctl_read.3
> +++ b/man/keyctl_read.3
> @@ -33,8 +33,8 @@ permission on a key to be able to read it.
>  and
>  .I buflen
>  specify the buffer into which the payload data will be placed.  If the buffer
> -is too small, the full size of the payload will be returned and no copy will
> -take place.
> +is too small, then the full size of the payload will be returned, and the
> +contents of the buffer may be overwritten in some undefined way.
>  .P
>  .BR keyctl_read_alloc ()
>  is similar to
> @@ -62,8 +62,8 @@ though the byte-ordering is as appropriate for the kernel.
>  On success
>  .BR keyctl_read ()
>  returns the amount of data placed into the buffer.  If the buffer was too
> -small, then the size of buffer required will be returned, but no data will be
> -transferred.
> +small, then the size of buffer required will be returned, and the contents of
> +the buffer may have been overwritten in some undefined way.
>  .P
>  On success
>  .BR keyctl_read_alloc ()
> -- 
> 2.15.0.403.gc27cc4dac6-goog
> 

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