Bug 538734 (CVE-2009-4021)

Summary: CVE-2009-4021 kernel: fuse: prevent fuse_put_request on invalid pointer
Product: [Other] Security Response Reporter: Eugene Teo (Security Response) <eteo>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED ERRATA QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: bhu, cebbert, davej, dhoward, jlieskov, jpirko, jskrabal, kyle, lgoncalv, lwang, mjc, williams
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
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Clone Of: Environment:
Last Closed: 2010-12-21 22:04:09 UTC Type: ---
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: 538735, 538736, 538737    
Bug Blocks:    

Description Eugene Teo (Security Response) 2009-11-19 09:02:33 UTC 
Description of problem:
fuse_direct_io() has a loop where requests are allocated in each iteration. if allocation fails, the loop is broken out and follows into an unconditional fuse_put_request() on that invalid pointer."

Upstream commit:
http://git.kernel.org/linus/f60311d5f7670d9539b424e4ed8b5c0872fc9e83

This can be triggered when the system is low on memory, and when the fuse_request_alloc() function called from fuse_get_req() fails. The fuse_put_request() function will then dereference the invalid pointer returned, resulting in a kernel oops.

This was introduced in 413ef8cb (v2.6.14-rc1) and fixed in v2.6.32-rc7.
Comment 2 Jan Lieskovsky 2009-11-25 16:55:30 UTC 
Mitre's CVE-2009-4021 entry:
----------------------------

The fuse_direct_io function in fs/fuse/file.c in the fuse subsystem in
the Linux kernel before 2.6.32-rc7 might allow attackers to cause a
denial of service (invalid pointer dereference and OOPS) via vectors
possibly related to a memory-consumption attack.
Comment 3 errata-xmlrpc 2010-01-19 23:36:53 UTC 
This issue has been addressed in following products:

  Red Hat Enterprise Linux 5

Via RHSA-2010:0046 https://rhn.redhat.com/errata/RHSA-2010-0046.html
Comment 4 errata-xmlrpc 2010-01-21 14:10:40 UTC 
This issue has been addressed in following products:

  MRG for RHEL-5

Via RHSA-2010:0041 https://rhn.redhat.com/errata/RHSA-2010-0041.html