Openwall GNU/*/Linux - a small security-enhanced Linux distro for servers
[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Date: Tue, 6 Aug 2019 11:36:15 -0400
From: Rich Felker <dalias@...c.org>
To: oss-security@...ts.openwall.com
Cc: musl@...ts.openwall.com
Subject: Re: [musl] CVE request: musl libc 1.1.23 and earlier x87 float stack
 imbalance

On Mon, Aug 05, 2019 at 08:05:39PM -0400, Rich Felker wrote:
> On Mon, Aug 05, 2019 at 07:27:37PM -0400, Rich Felker wrote:
> > I've discovered a flaw in musl libc's arch-specific math assembly code
> > for i386, whereby at least the log1p function and possibly others
> > return with more than one item on the x87 stack. This can lead to x87
> > stack overflow in the execution of subsequent math code, causing it to
> > incorrectly produce a NAN in place of the actual result. If floating
> > point results are used in flow control, this can lead to runaway wrong
> > code execution. For example, in Python (version 3.6.8 tested), at
> > least one code path of the dtoa function becomes an infinite loop
> > performing what's effectively an unbounded-length memset when entered
> > under such a condition.
> > 
> > This bug is potentially exploitable in software which calls affected
> > math functions with inputs under user control. Impact depends on how
> > the application handles the ABI-violating x87 state; in Python it
> > seems to be limited to producing a crash.
> > 
> > The bug is present in all versions after 0.9.12, up through the
> > current (1.1.23) release. Only 32-bit x86 systems (aka IA32, musl's
> > "i386" arch) are affected. Users of other archs, including x86_64, can
> > safely ignore this issue.
> > 
> > Affected users are advised to apply the following patch:
> > 
> > https://git.musl-libc.org/cgit/musl/patch/?id=f3ed8bfe8a82af1870ddc8696ed4cc1d5aa6b441
> 
> The patch contains an error that was missed for unknown reasons,
> probably failure to rebuild a file. I'm attaching an aggregate patch
> that works. Alternaatively, these two commits can be applied:
> 
> https://git.musl-libc.org/cgit/musl/patch/?id=f3ed8bfe8a82af1870ddc8696ed4cc1d5aa6b441
> https://git.musl-libc.org/cgit/musl/patch/?id=6818c31c9bc4bbad5357f1de14bedf781e5b349e

CVE-2019-14697 has been assigned for this issue.

Powered by blists - more mailing lists

Your e-mail address:

Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.