Bug 1284906

Summary:	cp will corrupt sparse files with trailing extents
Product:	Red Hat Enterprise Linux 7	Reporter:	Pádraig Brady <pbrady>
Component:	coreutils	Assignee:	Kamil Dudka <kdudka>
Status:	CLOSED ERRATA	QA Contact:	Jakub Prokes <jprokes>
Severity:	high	Docs Contact:	Petr Bokoc <pbokoc>
Priority:	urgent
Version:	7.2	CC:	fkrska, jkurik, jprokes, jscotka, pbokoc
Target Milestone:	rc	Keywords:	Patch, Reproducer, ZStream
Target Release:	---
Hardware:	All
OS:	Unspecified
Whiteboard:
Fixed In Version:	coreutils-8.22-16.el7	Doc Type:	Bug Fix
Doc Text:	Copying sparse files with trailing extents using "cp" no longer causes data corruption When creating sparse files, the fallocate utility could allocate extents beyond EOF using `FALLOC_FL_KEEP_SIZE`. As a consequence, when there was a gap (hole) between the extents, and EOF was within that gap, the final hole was not reproduced, which caused silent data corruption in the copied file due to its size being too small. With this update, the "cp" command ensures that extents beyond the apparent file size are not processed, as such processing and allocating is not currently supported. As a result, silent data corruption in certain type of sparse files no longer occurs.	Story Points:	---
Clone Of:
Clones:	1285365 (view as bug list)		Environment:
Last Closed:	2016-11-04 07:40:06 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	1285365

Description Pádraig Brady 2015-11-24 12:48:38 UTC

cp will corrupt copies of a file that has:

1. a hole up to the apparent size of the file.
2. an extent after the apparent EOF.

To reproduce:

echo blabla > sparse_falloc.in
truncate -s 2M sparse_falloc.in
fallocate -n -o 4M -l 1M sparse_falloc.in
cp sparse_falloc.in sparse_falloc.out
cmp sparse_falloc.in sparse_falloc.out || echo corrupt

Upstream backportable fix is at:
http://git.sv.gnu.org/gitweb/?p=coreutils.git;a=patch;h=eea6b49

Comment 1 Ondrej Vasik 2015-11-25 10:34:33 UTC

Thanks Pádraig for heads-up.

Comment 10 errata-xmlrpc 2016-11-04 07:40:06 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2016-2497.html