netdev - speaking of stacks

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 31 Mar 2008 09:15:56 -0400
From:	jamal <hadi@...erus.ca>
To:	netdev@...r.kernel.org
Cc:	Joern Engel <joern@...ybastard.org>,
	David Miller <davem@...emloft.net>,
	Herbert Xu <herbert@...dor.apana.org.au>
Subject: speaking of stacks

All this talk about stacks got me thirsty.
Heres something thats a mystery to me; probably very basic
when doing static check analysis (kernel make checkstack)

I have ipsec turned on in the linus git tree kernel and
net/xfrm/xfrm_user.c::xfrm_get_policy() shows up as one of
the top offenders. Eyeballing reveals that
struct xfrm_policy seems to be the offender 
in the else {} after if (p->index) in that function.
That seems understandable - once variable "tmp" is declared it goes
on the stack and it is freakin huge. 
However, checkstack only seems to catch it if i have the
line "memset(&tmp, 0, sizeof(struct xfrm_policy))". If i remove
that line - even though tmp is on the stack - checkstack doesnt catch
it.

What gives?

----
hadi@...sol:~$ gcc -v
Using built-in specs.
Target: i486-linux-gnu
Configured with: ../src/configure -v --enable-languages=c,c
++,fortran,objc,obj-c++,treelang --prefix=/usr --enable-shared
--with-system-zlib --libexecdir=/usr/lib --without-included-gettext
--enable-threads=posix --enable-nls --program-suffix=-4.1
--enable-__cxa_atexit --enable-clocale=gnu --enable-libstdcxx-debug
--enable-mpfr --with-tune=i686 --enable-checking=release i486-linux-gnu
Thread model: posix
gcc version 4.1.2 20061115 (prerelease) (Debian 4.1.1-21)
-----

Not a gcc guru by far.
Anyone interested, I can send you the .o before and after commenting
for your perusal.

cheers,
jamal

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html