Re: [PATCH 1/2] pipe: check limits only when increasing pipe capacity
flat view
From: Vegard Nossum <hidden>
Date: 2016-08-16 11:55:39
Also in:
lkml, stable
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.
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quoted hunk ↗ jump to hunk
--- 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 [off-list ref] Vegard