From: Hunter Adrian <adrian.hunter@nokia.com>
Date: Thu, 14 May 2009 04:32:30 +0000 (+0200)
Subject: UBIFS: return error if link and unlink race
X-Git-Tag: Release-2010-05/1~3^2~74
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=64427711828a05d54c1f99efab691a02d7134904;p=pandora-kernel.git

UBIFS: return error if link and unlink race

Consider a scenario when 'vfs_link(dirA/fileA)' and
'vfs_unlink(dirA/fileA, dirB/fileB)' race. 'vfs_link()' does not
lock 'dirA->i_mutex', so this is possible. Both of the functions
lock 'fileA->i_mutex' though. Suppose 'vfs_unlink()' wins, and takes
'fileA->i_mutex' mutex first. Suppose 'fileA->i_nlink' is 1. In this
case 'ubifs_unlink()' will drop the last reference, and put 'inodeA'
to the list of orphans. After this, 'vfs_link()' will link
'dirB/fileB' to 'inodeA'. Thir is a problem because, for example,
the subsequent 'vfs_unlink(dirB/fileB)' will add the same inode
to the list of orphans.

This problem was reported by J. R. Okajima <hooanon05@yahoo.co.jp>

[Artem: add more comments, amended commit message]

Signed-off-by: Adrian Hunter <adrian.hunter@nokia.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
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