Eric Paris 7d8b6c6375 CAPABILITIES: remove undefined caps from all processes ... This is effectively a revert of 7b9a7ec565 plus fixing it a different way... We found, when trying to run an application from an application which had dropped privs that the kernel does security checks on undefined capability bits. This was ESPECIALLY difficult to debug as those undefined bits are hidden from /proc/$PID/status. Consider a root application which drops all capabilities from ALL 4 capability sets. We assume, since the application is going to set eff/perm/inh from an array that it will clear not only the defined caps less than CAP_LAST_CAP, but also the higher 28ish bits which are undefined future capabilities. The BSET gets cleared differently. Instead it is cleared one bit at a time. The problem here is that in security/commoncap.c::cap_task_prctl() we actually check the validity of a capability being read. So any task which attempts to 'read all things set in bset' followed by 'unset all things set in bset' will not even attempt to unset the undefined bits higher than CAP_LAST_CAP. So the 'parent' will look something like: CapInh: 0000000000000000 CapPrm: 0000000000000000 CapEff: 0000000000000000 CapBnd: ffffffc000000000 All of this 'should' be fine. Given that these are undefined bits that aren't supposed to have anything to do with permissions. But they do... So lets now consider a task which cleared the eff/perm/inh completely and cleared all of the valid caps in the bset (but not the invalid caps it couldn't read out of the kernel). We know that this is exactly what the libcap-ng library does and what the go capabilities library does. They both leave you in that above situation if you try to clear all of you capapabilities from all 4 sets. If that root task calls execve() the child task will pick up all caps not blocked by the bset. The bset however does not block bits higher than CAP_LAST_CAP. So now the child task has bits in eff which are not in the parent. These are 'meaningless' undefined bits, but still bits which the parent doesn't have. The problem is now in cred_cap_issubset() (or any operation which does a subset test) as the child, while a subset for valid cap bits, is not a subset for invalid cap bits! So now we set durring commit creds that the child is not dumpable. Given it is 'more priv' than its parent. It also means the parent cannot ptrace the child and other stupidity. The solution here: 1) stop hiding capability bits in status This makes debugging easier! 2) stop giving any task undefined capability bits. it's simple, it you don't put those invalid bits in CAP_FULL_SET you won't get them in init and you won't get them in any other task either. This fixes the cap_issubset() tests and resulting fallout (which made the init task in a docker container untraceable among other things) 3) mask out undefined bits when sys_capset() is called as it might use ~0, ~0 to denote 'all capabilities' for backward/forward compatibility. This lets 'capsh --caps="all=eip" -- -c /bin/bash' run. 4) mask out undefined bit when we read a file capability off of disk as again likely all bits are set in the xattr for forward/backward compatibility. This lets 'setcap all+pe /bin/bash; /bin/bash' run Signed-off-by: Eric Paris <eparis@redhat.com> Reviewed-by: Kees Cook <keescook@chromium.org> Cc: Andrew Vagin <avagin@openvz.org> Cc: Andrew G. Morgan <morgan@kernel.org> Cc: Serge E. Hallyn <serge.hallyn@canonical.com> Cc: Kees Cook <keescook@chromium.org> Cc: Steve Grubb <sgrubb@redhat.com> Cc: Dan Walsh <dwalsh@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: James Morris <james.l.morris@oracle.com>		2014-07-24 21:53:47 +10:00
..
acpi	ACPI / i915: ignore firmware requests for backlight change	2014-07-07 23:38:05 +02:00
asm-generic	core: fix typo in percpu read_mostly section	2014-07-01 16:45:22 -04:00
clocksource
crypto	PKCS#7: Find intersection between PKCS#7 message and known, trusted keys	2014-07-08 13:50:15 +01:00
drm	sound fixes for 3.16-rc4	2014-07-04 08:56:57 -07:00
dt-bindings	This batch of fixes is for a handful of clock drivers from Allwinner,	2014-07-13 12:21:04 -07:00
keys	Merge remote-tracking branch 'integrity/next-with-keys' into keys-next	2014-07-22 21:54:43 +01:00
kvm
linux	CAPABILITIES: remove undefined caps from all processes	2014-07-24 21:53:47 +10:00
math-emu
media	Merge branch 'topic/omap3isp' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media	2014-06-12 23:04:28 -07:00
memory
misc
net	ipv4: fix dst race in sk_dst_get()	2014-06-25 17:41:44 -07:00
pcmcia
ras
rdma	Merge branches 'core', 'cxgb3', 'cxgb4', 'iser', 'iwpm', 'misc', 'mlx4', 'mlx5', 'noio', 'ocrdma', 'qib', 'srp' and 'usnic' into for-next	2014-06-10 10:12:14 -07:00
rxrpc
scsi	SCSI for-linus on 20140705	2014-07-06 12:08:30 -07:00
sound	ALSA: control: Protect user controls against concurrent access	2014-06-18 15:12:33 +02:00
target	target: Report correct response length for some commands	2014-06-11 12:15:30 -07:00
trace	tracing: Add __field_struct macro for TRACE_EVENT()	2014-06-21 00:18:42 -04:00
uapi	seccomp: implement SECCOMP_FILTER_FLAG_TSYNC	2014-07-18 12:13:40 -07:00
video	Merge branch 'drm-next' of git://people.freedesktop.org/~airlied/linux	2014-06-12 11:32:30 -07:00
xen	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next	2014-06-12 14:27:40 -07:00
Kbuild