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<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>LKML: Miklos Szeredi: [PATCH] private mounts</title><link href="/css/message.css" rel="stylesheet" type="text/css" /><link href="/css/wrap.css" rel="alternate stylesheet" type="text/css" title="wrap" /><link href="/css/nowrap.css" rel="stylesheet" type="text/css" title="nowrap" /><link href="/favicon.ico" rel="shortcut icon" /><script src="/js/simple-calendar.js" type="text/javascript"></script><script src="/js/styleswitcher.js" type="text/javascript"></script><link rel="alternate" type="application/rss+xml" title="lkml.org : last 100 messages" href="/rss.php" /><link rel="alternate" type="application/rss+xml" title="lkml.org : last messages by Miklos Szeredi" href="/groupie.php?aid=1702" /><script> var _paq = window._paq = window._paq || []; /* tracker methods like "setCustomDimension" should be called before "trackPageView" */ _paq.push(["setDoNotTrack", true]); _paq.push(["disableCookies"]); _paq.push(['trackPageView']); _paq.push(['enableLinkTracking']); (function() { var u="//m.lkml.org/"; _paq.push(['setTrackerUrl', u+'matomo.php']); _paq.push(['setSiteId', '1']); var d=document, g=d.createElement('script'), s=d.getElementsByTagName('script')[0]; g.async=true; g.src=u+'matomo.js'; s.parentNode.insertBefore(g,s); })(); </script></head><body onload="es.jasper.simpleCalendar.init();" itemscope="itemscope" itemtype="http://schema.org/BlogPosting"><table border="0" cellpadding="0" cellspacing="0"><tr><td width="180" align="center"><a href="/"><img style="border:0;width:135px;height:32px" src="/images/toprowlk.gif" alt="lkml.org" /></a></td><td width="32">聽</td><td class="nb"><div><a class="nb" href="/lkml"> [lkml]</a> 聽 <a class="nb" href="/lkml/2005"> [2005]</a> 聽 <a class="nb" href="/lkml/2005/4"> [Apr]</a> 聽 <a class="nb" href="/lkml/2005/4/24"> [24]</a> 聽 <a class="nb" href="/lkml/last100"> [last100]</a> 聽 <a href="/rss.php"><img src="/images/rss-or.gif" border="0" alt="RSS Feed" /></a></div><div>Views: <a href="#" class="nowrap" onclick="setActiveStyleSheet('wrap');return false;">[wrap]</a><a href="#" class="wrap" onclick="setActiveStyleSheet('nowrap');return false;">[no wrap]</a> 聽 <a class="nb" href="/lkml/mheaders/2005/4/24/76" onclick="this.href='/lkml/headers'+'/2005/4/24/76';">[headers]</a>聽 <a href="/lkml/bounce/2005/4/24/76">[forward]</a>聽 </div></td><td width="32">聽</td></tr><tr><td valign="top"><div class="es-jasper-simpleCalendar" baseurl="/lkml/"></div><div class="threadlist">Messages in this thread</div><ul class="threadlist"><li class="root"><a href="/lkml/2005/4/24/76">First message in thread</a></li><li class="origin"><a href="/lkml/2005/4/24/77">Miklos Szeredi</a><ul><li><a href="/lkml/2005/4/24/77">Al Viro</a><ul><li><a href="/lkml/2005/4/24/86">Miklos Szeredi</a></li></ul></li><li><a href="/lkml/2005/4/24/79">Christoph Hellwig</a><ul><li><a href="/lkml/2005/4/24/87">Miklos Szeredi</a><ul><li><a href="/lkml/2005/4/24/88">Al Viro</a><ul><li><a href="/lkml/2005/4/24/89">Miklos Szeredi</a></li></ul></li></ul></li></ul></li></ul></li></ul><div class="threadlist">Patch in this message</div><ul class="threadlist"><li><a href="/lkml/diff/2005/4/24/76/1">Get diff 1</a></li></ul></td><td width="32" rowspan="2" class="c" valign="top"><img src="/images/icornerl.gif" width="32" height="32" alt="/" /></td><td class="c" rowspan="2" valign="top" style="padding-top: 1em"><table><tr><td><table><tr><td class="lp">Subject</td><td class="rp" itemprop="name">[PATCH] private mounts</td></tr><tr><td class="lp">From</td><td class="rp" itemprop="author">Miklos Szeredi <></td></tr><tr><td class="lp">Date</td><td class="rp" itemprop="datePublished">Sun, 24 Apr 2005 22:08:13 +0200</td></tr></table></td><td></td></tr></table><pre itemprop="articleBody">This simple patch adds support for private (or invisible) mounts. The rationale is to allow mounts to be private for a user but still in the global namespace. An immediate user of this would be FUSE, which currently achieves the hiding of data with inode->permission(), which is less elegant. Christoph, I'm specially interested in your opinion, since you were so strongly opposed to the current solution in FUSE. Performance measurements indicate that the overhead is about 2% of the time spent following mounts, or 6ns per-mount on a 533 Celeron. This patch does: - add new mount flag: MS_PRIVATE / MNT_PRIVATE - add new member in struct vfsmount: mnt_uid - if MNT_PRIVATE is set, set mnt_uid to current->fsuid in do_add_mount() and do_remount() - in clone_mnt() copy mnt_uid to the new mount - in lookup_mnt() while looping through the hash chain for the mountpoint, check if the mount is "visible" for this process, and skip it if not Comments are appreciated. If there are no vetoes agains the patch, I think it's suitable for -mm. Thanks, Miklos Signed-off-by: Miklos Szeredi <miklos@szeredi.hu> diff -rup orig/linux-2.6.11/fs/namespace.c linux-2.6.11/fs/namespace.c --- orig/linux-2.6.11/fs/namespace.c 2005-03-04 23:18:48.000000000 +0100 +++ linux-2.6.11/fs/namespace.c 2005-04-24 12:44:41.000000000 +0200 @@ -81,6 +81,15 @@ void free_vfsmnt(struct vfsmount *mnt) } /* + * Check if this mount should be skipped or not + */ +static inline int mnt_visible(struct vfsmount *mnt) +{ + return !(mnt->mnt_flags & MNT_PRIVATE) || + mnt->mnt_uid == current->fsuid; +} + +/* * Now, lookup_mnt increments the ref count before returning * the vfsmount struct. */ @@ -97,7 +106,8 @@ struct vfsmount *lookup_mnt(struct vfsmo if (tmp == head) break; p = list_entry(tmp, struct vfsmount, mnt_hash); - if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) { + if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry && + mnt_visible(p)) { found = mntget(p); break; } @@ -155,6 +165,7 @@ clone_mnt(struct vfsmount *old, struct d if (mnt) { mnt->mnt_flags = old->mnt_flags; + mnt->mnt_uid = old->mnt_uid; atomic_inc(&sb->s_active); mnt->mnt_sb = sb; mnt->mnt_root = dget(root); @@ -234,6 +245,7 @@ static int show_vfsmnt(struct seq_file * { MNT_NOSUID, ",nosuid" }, { MNT_NODEV, ",nodev" }, { MNT_NOEXEC, ",noexec" }, + { MNT_PRIVATE, ",private" }, { 0, NULL } }; struct proc_fs_info *fs_infop; @@ -252,6 +264,8 @@ static int show_vfsmnt(struct seq_file * if (mnt->mnt_flags & fs_infop->flag) seq_puts(m, fs_infop->str); } + if (mnt->mnt_flags & MNT_PRIVATE) + seq_printf(m, ",mnt_uid=%u", mnt->mnt_uid); if (mnt->mnt_sb->s_op->show_options) err = mnt->mnt_sb->s_op->show_options(m, mnt); seq_puts(m, " 0 0\n"); @@ -684,8 +698,11 @@ static int do_remount(struct nameidata * down_write(&sb->s_umount); err = do_remount_sb(sb, flags, data, 0); - if (!err) + if (!err) { nd->mnt->mnt_flags=mnt_flags; + if (mnt_flags & MNT_PRIVATE) + nd->mnt->mnt_uid = current->fsuid; + } up_write(&sb->s_umount); if (!err) security_sb_post_remount(nd->mnt, flags, data); @@ -807,6 +824,8 @@ int do_add_mount(struct vfsmount *newmnt goto unlock; newmnt->mnt_flags = mnt_flags; + if (mnt_flags & MNT_PRIVATE) + newmnt->mnt_uid = current->fsuid; err = graft_tree(newmnt, nd); if (err == 0 && fslist) { @@ -1033,7 +1052,9 @@ long do_mount(char * dev_name, char * di mnt_flags |= MNT_NODEV; if (flags & MS_NOEXEC) mnt_flags |= MNT_NOEXEC; - flags &= ~(MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_ACTIVE); + if (flags & MS_PRIVATE) + mnt_flags |= MNT_PRIVATE; + flags &= ~(MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_PRIVATE|MS_ACTIVE); /* ... and get the mountpoint */ retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd); diff -rup orig/linux-2.6.11/include/linux/fs.h linux-2.6.11/include/linux/fs.h --- orig/linux-2.6.11/include/linux/fs.h 2005-03-04 23:19:05.000000000 +0100 +++ linux-2.6.11/include/linux/fs.h 2005-04-24 10:23:33.000000000 +0200 @@ -96,6 +96,7 @@ extern int dir_notify_enable; #define MS_REMOUNT 32 /* Alter flags of a mounted FS */ #define MS_MANDLOCK 64 /* Allow mandatory locks on an FS */ #define MS_DIRSYNC 128 /* Directory modifications are synchronous */ +#define MS_PRIVATE 256 /* Make this mount invisible to other users */ #define MS_NOATIME 1024 /* Do not update access times. */ #define MS_NODIRATIME 2048 /* Do not update directory access times */ #define MS_BIND 4096 diff -rup orig/linux-2.6.11/include/linux/mount.h linux-2.6.11/include/linux/mount.h --- orig/linux-2.6.11/include/linux/mount.h 2004-12-25 11:52:55.000000000 +0100 +++ linux-2.6.11/include/linux/mount.h 2005-04-24 10:24:29.000000000 +0200 @@ -19,6 +19,7 @@ #define MNT_NOSUID 1 #define MNT_NODEV 2 #define MNT_NOEXEC 4 +#define MNT_PRIVATE 8 struct vfsmount { @@ -31,6 +32,7 @@ struct vfsmount struct list_head mnt_child; /* and going through their mnt_child */ atomic_t mnt_count; int mnt_flags; + uid_t mnt_uid; int mnt_expiry_mark; /* true if marked for expiry */ char *mnt_devname; /* Name of device e.g. /dev/dsk/hda1 */ struct list_head mnt_list; - 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 <a href="http://vger.kernel.org/majordomo-info.html">http://vger.kernel.org/majordomo-info.html</a> Please read the FAQ at <a href="http://www.tux.org/lkml/">http://www.tux.org/lkml/</a> </pre></td><td width="32" rowspan="2" class="c" valign="top"><img src="/images/icornerr.gif" width="32" height="32" alt="\" /></td></tr><tr><td align="right" valign="bottom"> 聽 </td></tr><tr><td align="right" valign="bottom">聽</td><td class="c" valign="bottom" style="padding-bottom: 0px"><img src="/images/bcornerl.gif" width="32" height="32" alt="\" /></td><td class="c">聽</td><td class="c" valign="bottom" style="padding-bottom: 0px"><img src="/images/bcornerr.gif" width="32" height="32" alt="/" /></td></tr><tr><td align="right" valign="top" colspan="2"> 聽 </td><td class="lm">Last update: 2005-04-24 22:12 聽聽 [from the cache] 漏2003-2020 <a href="http://blog.jasper.es/">Jasper Spaans</a>|hosted at <a href="https://www.digitalocean.com/?refcode=9a8e99d24cf9">Digital Ocean</a> and my Meterkast|<a href="http://blog.jasper.es/categories.html#lkml-ref">Read the blog</a></td><td>聽</td></tr></table><script language="javascript" src="/js/styleswitcher.js" type="text/javascript"></script></body></html>