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Date: Fri, 07 Dec 2007 14:11:05 +0300 From: "Denis V. Lunev" <den@...ru> To: Andrew Morton <akpm@...ux-foundation.org> CC: David Woodhouse <dwmw2@...radead.org>, "Eric W. Biederman" <ebiederm@...ssion.com>, Linus Torvalds <torvalds@...ux-foundation.org>, "Rafael J. Wysocki" <rjw@...k.pl>, Pavel Machek <pavel@....cz>, kernel list <linux-kernel@...r.kernel.org>, netdev <netdev@...r.kernel.org>, Pavel Emelyanov <xemul@...nvz.org>, "Denis V. Lunev" <den@...nvz.org> Subject: Re: [PATCH 2.6.24-rc3] Fix /proc/net breakage Andrew Morton wrote: > On Fri, 07 Dec 2007 04:51:37 +0000 David Woodhouse <dwmw2@...radead.org> wrote: > >> On Mon, 2007-11-26 at 15:17 -0700, Eric W. Biederman wrote: >>> Well I clearly goofed when I added the initial network namespace support >>> for /proc/net. Currently things work but there are odd details visible >>> to user space, even when we have a single network namespace. >>> >>> Since we do not cache proc_dir_entry dentries at the moment we can >>> just modify ->lookup to return a different directory inode depending >>> on the network namespace of the process looking at /proc/net, replacing >>> the current technique of using a magic and fragile follow_link method. >>> >>> To accomplish that this patch: >>> - introduces a shadow_proc method to allow different dentries to >>> be returned from proc_lookup. >>> - Removes the old /proc/net follow_link magic >>> - Fixes a weakness in our not caching of proc generic dentries. >>> >>> As shadow_proc uses a task struct to decided which dentry to return we >>> can go back later and fix the proc generic caching without modifying any code that >>> uses the shadow_proc method. >>> >>> Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com> >>> --- >>> fs/proc/generic.c | 12 ++++++- >>> fs/proc/proc_net.c | 86 +++-------------------------------------------- >>> include/linux/proc_fs.h | 3 ++ >>> 3 files changed, 19 insertions(+), 82 deletions(-) >> (commit 2b1e300a9dfc3196ccddf6f1d74b91b7af55e416) >> >> This seems to have broken the use of /proc/bus/usb as a mountpoint. It >> always appears empty now, whatever's supposed to be mounted there. >> > > Yes. Denis and Eric are tossing around competing patches but afaik nobody > is happy with any of them. Guys, could we get this sorted soonish please? > Andrew, I become too relaxed after receiving "Tested-by: Giacomo Catenazzi <cate@...ian.org>" Eric, I believe that reverting an original behavior is better than your new one as - you introduce search into the depth by calling have_submounts(dentry) during revalidation for all(!) /proc dentries - your shadowing behavior will be broken if you'll mount something in the depth of shadowed tree (this can be done as a DoS attempt) As a last minute call, may be it will be better to pin network namespace like a pid namespace during mount to avoid this crap at all? Regards, Den -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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