From: Al Viro <viro@zeniv.linux.org.uk>
Date: Fri, 29 Oct 2010 07:30:42 +0000 (-0400)
Subject: fix open/umount race
X-Git-Tag: v2.6.37-rc1~44^2~27
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d893f1bc2a9f0f7dcb4b433452c59f9bedac0d7d;p=pandora-kernel.git

fix open/umount race

nameidata_to_filp() drops nd->path or transfers it to opened
file.  In the former case it's a Bad Idea(tm) to do mnt_drop_write()
on nd->path.mnt, since we might race with umount and vfsmount in
question might be gone already.

Fix: don't drop it, then...  IOW, have nameidata_to_filp() grab nd->path
in case it transfers it to file and do path_drop() in callers.  After
they are through with accessing nd->path...

Reported-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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