Bug 248353 - (CVE-2007-3732) CVE-2007-3732 kernel: Reset %fs early in iret_exc
CVE-2007-3732 kernel: Reset %fs early in iret_exc
Status: CLOSED ERRATA
Product: Security Response
Classification: Other
Component: vulnerability (Show other bugs)
unspecified
All Linux
high Severity high
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Assigned To: Red Hat Product Security
impact=important,source=kernelsec,rep...
: Security
Depends On:
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Reported: 2007-07-16 08:03 EDT by Marcel Holtmann
Modified: 2010-04-15 22:07 EDT (History)
1 user (show)

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Doc Type: Bug Fix
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Last Closed: 2010-04-15 22:02:37 EDT
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Description Marcel Holtmann 2007-07-16 08:03:17 EDT
The iret_exc fixup path, run when iret generates an exception due to bogus
%cs:%eip or %ss:%esp on the way back to user mode, has been broken since the
%fs-percpu-current changes.  The kernel's %fs needs to be restored before the
call in TRACE_IRQS_ON and before enabling interrupts, so that "current"
references work.  Without this, "current" used in the window between iret_exc
and the middle of error_code where %fs is reset, would crash (or get bogus
values, perhaps exploitable in fancy ways).
Comment 2 Eugene Teo (Security Response) 2010-04-15 22:02:37 EDT
Upstream commit:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=a10d9a71bafd3a283da240d2868e71346d2aef6f

Commit a10d9a71 is the fix for CVE-2007-3732. When this patch was backported to the -stable kernel, it was wrongly listed as CVE-2007-3731. And when we were dealing with CVE-2007-3731, our developer backported this patch too even though we have filed a separate bug for CVE-2007-3732, so this was fixed. What a mess, but I'm glad we cleared this up afterall.

https://bugzilla.redhat.com/show_bug.cgi?id=248324#c4
https://bugzilla.redhat.com/show_bug.cgi?id=248324#c7

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