grsecurity/PaX problem causing /sbin/killall5 to break

[lcm]

Hello.

I am running:

Linux intscan2 2.4.26-grsec #1 SMP Thu Aug 5 15:40:40 EDT 2004 i686 GNU/Linux

on debian.

I've noticed something strange. On going to single user, killall5 does not kill all the processes on the box, in fact it kills no process. I have used chpax and played with the settings, thinking this was a PaX issue, but no combination of seems to let killall5 do it's job. Here are the current settings:

intscan2:/home/lcm/chpax-0.7# ./chpax -v /sbin/killall5

----[ chpax 0.7 : Current flags for /sbin/killall5 (pemrxs) ]----

* Paging based PAGE_EXEC : disabled
* Trampolines : not emulated
* mprotect() : not restricted
* mmap() base : not randomized
* ET_EXEC base : not randomized
* Segmentation based PAGE_EXEC : disabled

I compiled the kernel with the default settings for PaX. All tests wre run with grsecurity disabled.

I've tried running killall5 through strace, but seems like I am hitting a race condition, because that horribly hangs the machine.

Any pointers would be appreciated.

Thanks,

-lcm

[spender]

So grsecurity is disabled? Can you post the grsecurity/pax sections of your config?

-Brad

[lcm]

# Grsecurity
#
CONFIG_GRKERNSEC=y
CONFIG_CRYPTO=y
CONFIG_CRYPTO_SHA256=y
# CONFIG_GRKERNSEC_LOW is not set
# CONFIG_GRKERNSEC_MID is not set
# CONFIG_GRKERNSEC_HI is not set
CONFIG_GRKERNSEC_CUSTOM=y
# PaX Control
#
# CONFIG_GRKERNSEC_PAX_SOFTMODE is not set
CONFIG_GRKERNSEC_PAX_EI_PAX=y
CONFIG_GRKERNSEC_PAX_PT_PAX_FLAGS=y
CONFIG_GRKERNSEC_PAX_NO_ACL_FLAGS=y
# CONFIG_GRKERNSEC_PAX_HAVE_ACL_FLAGS is not set
# CONFIG_GRKERNSEC_PAX_HOOK_ACL_FLAGS is not set

#
# Address Space Protection
#
CONFIG_GRKERNSEC_PAX_NOEXEC=y
CONFIG_GRKERNSEC_PAX_PAGEEXEC=y
CONFIG_GRKERNSEC_PAX_SEGMEXEC=y
# CONFIG_GRKERNSEC_PAX_EMUTRAMP is not set
CONFIG_GRKERNSEC_PAX_MPROTECT=y
# CONFIG_GRKERNSEC_PAX_NOELFRELOCS is not set
CONFIG_GRKERNSEC_PAX_ASLR=y
CONFIG_GRKERNSEC_PAX_RANDKSTACK=y
CONFIG_GRKERNSEC_PAX_RANDUSTACK=y
CONFIG_GRKERNSEC_PAX_RANDMMAP=y
CONFIG_GRKERNSEC_PAX_RANDEXEC=y
CONFIG_GRKERNSEC_KMEM=y
# CONFIG_GRKERNSEC_IO is not set
CONFIG_GRKERNSEC_PROC_MEMMAP=y
# CONFIG_GRKERNSEC_HIDESYM is not set

#
# Role Based Access Control Options
#
CONFIG_GRKERNSEC_ACL_HIDEKERN=y
CONFIG_GRKERNSEC_ACL_MAXTRIES=3
CONFIG_GRKERNSEC_ACL_TIMEOUT=30

#
# Filesystem Protections
#
CONFIG_GRKERNSEC_PROC=y
# CONFIG_GRKERNSEC_PROC_USER is not set
CONFIG_GRKERNSEC_PROC_USERGROUP=y
CONFIG_GRKERNSEC_PROC_GID=1001
CONFIG_GRKERNSEC_PROC_ADD=y
CONFIG_GRKERNSEC_LINK=y
CONFIG_GRKERNSEC_FIFO=y
CONFIG_GRKERNSEC_CHROOT=y
CONFIG_GRKERNSEC_CHROOT_MOUNT=y
CONFIG_GRKERNSEC_CHROOT_DOUBLE=y
CONFIG_GRKERNSEC_CHROOT_PIVOT=y
CONFIG_GRKERNSEC_CHROOT_CHDIR=y
CONFIG_GRKERNSEC_CHROOT_CHMOD=y
CONFIG_GRKERNSEC_CHROOT_FCHDIR=y
CONFIG_GRKERNSEC_CHROOT_MKNOD=y
CONFIG_GRKERNSEC_CHROOT_SHMAT=y
CONFIG_GRKERNSEC_CHROOT_UNIX=y
CONFIG_GRKERNSEC_CHROOT_FINDTASK=y
CONFIG_GRKERNSEC_CHROOT_NICE=y
CONFIG_GRKERNSEC_CHROOT_SYSCTL=y
CONFIG_GRKERNSEC_CHROOT_CAPS=y

#
# Kernel Auditing
#
# CONFIG_GRKERNSEC_AUDIT_GROUP is not set
CONFIG_GRKERNSEC_EXECLOG=y
CONFIG_GRKERNSEC_RESLOG=y
CONFIG_GRKERNSEC_CHROOT_EXECLOG=y
CONFIG_GRKERNSEC_AUDIT_CHDIR=y
CONFIG_GRKERNSEC_AUDIT_MOUNT=y
CONFIG_GRKERNSEC_AUDIT_IPC=y
CONFIG_GRKERNSEC_SIGNAL=y
CONFIG_GRKERNSEC_FORKFAIL=y
CONFIG_GRKERNSEC_TIME=y
# CONFIG_GRKERNSEC_PROC_IPADDR is not set
# CONFIG_GRKERNSEC_AUDIT_TEXTREL is not set

#
# Executable Protections
#
CONFIG_GRKERNSEC_EXECVE=y
CONFIG_GRKERNSEC_DMESG=y
CONFIG_GRKERNSEC_RANDPID=y
# CONFIG_GRKERNSEC_TPE is not set

#
# Network Protections
#
CONFIG_GRKERNSEC_RANDNET=y
CONFIG_GRKERNSEC_RANDISN=y
CONFIG_GRKERNSEC_RANDID=y
CONFIG_GRKERNSEC_RANDSRC=y
CONFIG_GRKERNSEC_RANDRPC=y
# CONFIG_GRKERNSEC_SOCKET is not set

#
# Sysctl support
#
CONFIG_GRKERNSEC_SYSCTL=y

#
# Logging options
#
CONFIG_GRKERNSEC_FLOODTIME=10
CONFIG_GRKERNSEC_FLOODBURST=4

[spender]

Do the results change at all if you disable PaX completely in the configuration itself, and what about if you disable grsecurity from the config?

-Brad

[lcm]

A clean compile, without grsecurity or PaX works.

After many kenerl builds, the problem is:

CONFIG_GRKERNSEC_PROC_MEMMAP

With this disabled, killall5 works as you would expect.

btw, the strace /sbin/killall5 hang problem exists on 2.4.26 unpatched with grsecurity. Is this a known 'hang the kernel' bug? Pretty bad, since I can run it as non root and the system still hangs. Looks like a race condition somewhere in trace and kill.

[spender]

The code for that feature looks fine to me. Are you able to duplicate this problem with the latest version of grsecurity on 2.4.27?

-Brad

[bcoudurier]

I can confirm that the problem is still appearing running 2.4.28 with latest grsecurity patch (11/23)

When i disable CONFIG_GRKERNSEC_PROC_MEMMAP everything works just fine.

Here is my kernel configuration :
# CONFIG_GRKERNSEC_PAX_SOFTMODE is not set
CONFIG_GRKERNSEC_PAX_EI_PAX=y
# CONFIG_GRKERNSEC_PAX_PT_PAX_FLAGS is not set
CONFIG_GRKERNSEC_PAX_NO_ACL_FLAGS=y
# CONFIG_GRKERNSEC_PAX_HAVE_ACL_FLAGS is not set
# CONFIG_GRKERNSEC_PAX_HOOK_ACL_FLAGS is not set

CONFIG_GRKERNSEC_PAX_NOEXEC=y
CONFIG_GRKERNSEC_PAX_PAGEEXEC=y
CONFIG_GRKERNSEC_PAX_SEGMEXEC=y
# CONFIG_GRKERNSEC_PAX_EMUTRAMP is not set
CONFIG_GRKERNSEC_PAX_MPROTECT=y
CONFIG_GRKERNSEC_PAX_NOELFRELOCS=y
# CONFIG_GRKERNSEC_PAX_KERNEXEC is not set
CONFIG_GRKERNSEC_PAX_ASLR=y
CONFIG_GRKERNSEC_PAX_RANDKSTACK=y
CONFIG_GRKERNSEC_PAX_RANDUSTACK=y
CONFIG_GRKERNSEC_PAX_RANDMMAP=y
CONFIG_GRKERNSEC_PAX_RANDEXEC=y
CONFIG_GRKERNSEC_KMEM=y
CONFIG_GRKERNSEC_IO=y
CONFIG_RTC=y
CONFIG_GRKERNSEC_PROC_MEMMAP=y
CONFIG_GRKERNSEC_BRUTE=y
CONFIG_GRKERNSEC_HIDESYM=y

# CONFIG_GRKERNSEC_ACL_HIDEKERN is not set
CONFIG_GRKERNSEC_ACL_MAXTRIES=3
CONFIG_GRKERNSEC_ACL_TIMEOUT=30

CONFIG_GRKERNSEC_PROC=y
# CONFIG_GRKERNSEC_PROC_USER is not set
CONFIG_GRKERNSEC_PROC_USERGROUP=y
CONFIG_GRKERNSEC_PROC_GID=104
CONFIG_GRKERNSEC_PROC_ADD=y
CONFIG_GRKERNSEC_LINK=y
CONFIG_GRKERNSEC_FIFO=y
CONFIG_GRKERNSEC_CHROOT=y
CONFIG_GRKERNSEC_CHROOT_MOUNT=y
CONFIG_GRKERNSEC_CHROOT_DOUBLE=y
CONFIG_GRKERNSEC_CHROOT_PIVOT=y
CONFIG_GRKERNSEC_CHROOT_CHDIR=y
CONFIG_GRKERNSEC_CHROOT_CHMOD=y
CONFIG_GRKERNSEC_CHROOT_FCHDIR=y
CONFIG_GRKERNSEC_CHROOT_MKNOD=y
CONFIG_GRKERNSEC_CHROOT_SHMAT=y
CONFIG_GRKERNSEC_CHROOT_UNIX=y
CONFIG_GRKERNSEC_CHROOT_FINDTASK=y
CONFIG_GRKERNSEC_CHROOT_NICE=y
CONFIG_GRKERNSEC_CHROOT_SYSCTL=y
CONFIG_GRKERNSEC_CHROOT_CAPS=y

# CONFIG_GRKERNSEC_AUDIT_GROUP is not set
# CONFIG_GRKERNSEC_EXECLOG is not set
CONFIG_GRKERNSEC_RESLOG=y
# CONFIG_GRKERNSEC_CHROOT_EXECLOG is not set
# CONFIG_GRKERNSEC_AUDIT_CHDIR is not set
CONFIG_GRKERNSEC_AUDIT_MOUNT=y
# CONFIG_GRKERNSEC_AUDIT_IPC is not set
CONFIG_GRKERNSEC_SIGNAL=y
CONFIG_GRKERNSEC_FORKFAIL=y
CONFIG_GRKERNSEC_TIME=y
CONFIG_GRKERNSEC_PROC_IPADDR=y
# CONFIG_GRKERNSEC_AUDIT_TEXTREL is not set

CONFIG_GRKERNSEC_EXECVE=y
CONFIG_GRKERNSEC_DMESG=yCONFIG_GRKERNSEC_RANDPID=y
CONFIG_GRKERNSEC_TPE=y
# CONFIG_GRKERNSEC_TPE_ALL is not set
CONFIG_GRKERNSEC_TPE_GID=105

CONFIG_GRKERNSEC_RANDNET=y
CONFIG_GRKERNSEC_RANDISN=y
CONFIG_GRKERNSEC_RANDID=y
CONFIG_GRKERNSEC_RANDSRC=y
CONFIG_GRKERNSEC_RANDRPC=y
CONFIG_GRKERNSEC_SOCKET=y
# CONFIG_GRKERNSEC_SOCKET_ALL is not set
# CONFIG_GRKERNSEC_SOCKET_CLIENT is not set
CONFIG_GRKERNSEC_SOCKET_SERVER=y
CONFIG_GRKERNSEC_SOCKET_SERVER_GID=106

# CONFIG_GRKERNSEC_SYSCTL is not set

CONFIG_GRKERNSEC_FLOODTIME=10
CONFIG_GRKERNSEC_FLOODBURST=4

Thks

[spender]

If you google for this problem, you will see many people reporting it who are not using grsec. The code for PROC_MEMMAP is trivial and can't cause the hangs being reported. If anything, it's simply making a race condition already present in the kernel more reproducible.

-Brad