From: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Date: Fri, 6 Feb 2009 20:59:26 +0000 (-0600)
Subject: vfs: Don't call attach_nobh_buffers() with an empty list
X-Git-Tag: v2.6.29-rc4~13
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d4cf109f05ff04c6f5065c3e14165ef01a57dd53;p=pandora-kernel.git

vfs: Don't call attach_nobh_buffers() with an empty list

This is a modification of a patch by Bill Pemberton <wfp5p@virginia.edu>

nobh_write_end() could call attach_nobh_buffers() with head == NULL.
This would result in a trap when attach_nobh_buffers() attempted to
access bh->b_this_page.

This can be illustrated by running the writev01 testcase from LTP on jfs.

This error was introduced by commit 5b41e74a "vfs: fix data leak in
nobh_write_end()".  That patch did not take into account that if
PageMappedToDisk() is true upon entry to nobh_write_begin(), then no
buffers will be allocated for the page.  In that case, we won't have to
worry about a failed write leaving unitialized data in the page.

Of course, head != NULL implies !page_has_buffers(page), so no need to
test both.

Signed-off-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Cc: Bill Pemberton <wfp5p@virginia.edu>
Cc: Dmitri Monakhov <dmonakhov@openvz.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

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