Messages in this thread | | | Subject | Re: [PATCH 1/2] pipe: check limits only when increasing pipe capacity | From | Vegard Nossum <> | Date | Tue, 16 Aug 2016 13:55:01 +0200 |
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On 08/16/2016 01:10 PM, Michael Kerrisk (man-pages) wrote: > When changing a pipe's capacity with fcntl(F_SETPIPE_SZ), various > limits defined by /proc/sys/fs/pipe-* files are checked to see > if unprivileged users are exceeding limits on memory consumption. > [...]
> --- > fs/pipe.c | 25 +++++++++++++++++-------- > 1 file changed, 17 insertions(+), 8 deletions(-) > > diff --git a/fs/pipe.c b/fs/pipe.c > index 4ebe6b2..a98ebca 100644 > --- a/fs/pipe.c > +++ b/fs/pipe.c > @@ -1122,14 +1122,23 @@ long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg) > if (!nr_pages) > goto out; > > - if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) { > - ret = -EPERM; > - goto out; > - } else if ((too_many_pipe_buffers_hard(pipe->user) || > - too_many_pipe_buffers_soft(pipe->user)) && > - !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) { > - ret = -EPERM; > - goto out; > + /* > + * If trying to increase the pipe capacity, check that an > + * unprivileged user is not trying to exceed various limits. > + * (Decreasing the pipe capacity is always permitted, even > + * if the user is currently over a limit.) > + */ > + if (nr_pages > pipe->buffers) { > + if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) { > + ret = -EPERM; > + goto out; > + } else if ((too_many_pipe_buffers_hard(pipe->user) || > + too_many_pipe_buffers_soft(pipe->user)) && > + !capable(CAP_SYS_RESOURCE) && > + !capable(CAP_SYS_ADMIN)) { > + ret = -EPERM; > + goto out; > + } > } > ret = pipe_set_size(pipe, nr_pages); > break; >
FWIW: Reviewed-by: Vegard Nossum <vegard.nossum@oracle.com>
Vegard
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