lkml.org 
[lkml]   [2011]   [Apr]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [RFC] [PATCH] drop_pagecache syscall
    On Wed, Apr 27, 2011 at 05:10:41AM -0400, Mike Frysinger wrote:
    > On Wed, Apr 27, 2011 at 05:01, Andrea Righi wrote:
    > > On Wed, Apr 27, 2011 at 10:14:53AM +1000, Dave Chinner wrote:
    > >> On Tue, Apr 26, 2011 at 11:35:27PM +0200, Andrea Righi wrote:
    > >> > This functionality can be used by all the applications that want to have a
    > >> > better control over the page cache management (for example to immediately drop
    > >> > pages that for sure will not be reused in the near future, without calling
    > >> > posix_fadvise() for all the files they've touched), or to provide a more fine
    > >> > grained debugging feature usable by the filesystem benchmarks.
    > >> >
    > >> > The system call does not require root privileges and it can be called by any
    > >> > unprivileged application. For example, we can write a userspace tool to run
    > >> > something like this:
    > >> >
    > >> >   $ drop-pagecache /path/file_or_dir
    > >>
    > >> That's a potential DOS vector, I think. Drop the pagecache in a hard
    > >> loop on the root fs of a busy server and watch it crawl...
    > >
    > > Yes, probably we could allow only the CAP_SYS_ADMIN tasks to execute
    > > this syscall.
    >
    > if /proc/sys/vm/drop_caches has any checks other than file permission
    > checks (i.e. UID==0), it'd probably be better to copy those rather
    > than picking something different.

    ok, what about checking current_euid() == 0?

    Thanks,
    -Andrea
    --
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2011-04-27 11:49    [W:0.025 / U:119.964 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site