Eric W. Biederman a2a1be2de7 signal: Extend exec_id to 64bits ... commit d1e7fd6462 upstream. Replace the 32bit exec_id with a 64bit exec_id to make it impossible to wrap the exec_id counter. With care an attacker can cause exec_id wrap and send arbitrary signals to a newly exec'd parent. This bypasses the signal sending checks if the parent changes their credentials during exec. The severity of this problem can been seen that in my limited testing of a 32bit exec_id it can take as little as 19s to exec 65536 times. Which means that it can take as little as 14 days to wrap a 32bit exec_id. Adam Zabrocki has succeeded wrapping the self_exe_id in 7 days. Even my slower timing is in the uptime of a typical server. Which means self_exec_id is simply a speed bump today, and if exec gets noticably faster self_exec_id won't even be a speed bump. Extending self_exec_id to 64bits introduces a problem on 32bit architectures where reading self_exec_id is no longer atomic and can take two read instructions. Which means that is is possible to hit a window where the read value of exec_id does not match the written value. So with very lucky timing after this change this still remains expoiltable. I have updated the update of exec_id on exec to use WRITE_ONCE and the read of exec_id in do_notify_parent to use READ_ONCE to make it clear that there is no locking between these two locations. Link: https://lore.kernel.org/kernel-hardening/20200324215049.GA3710@pi3.com.pl Fixes: 2.3.23pre2 Cc: stable@vger.kernel.org Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2020-04-17 10:48:47 +02:00
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acpi	ACPICA: Introduce ACPI_ACCESS_BYTE_WIDTH() macro	2020-03-05 16:42:17 +01:00
asm-generic
clocksource
crypto
drm	drm/panel: make drm_panel.h self-contained	2020-01-27 14:51:01 +01:00
dt-bindings	dt-bindings: reset: meson8b: fix duplicate reset IDs	2020-01-23 08:21:26 +01:00
keys
kvm
linux	signal: Extend exec_id to 64bits	2020-04-17 10:48:47 +02:00
math-emu
media	media: v4l2-device.h: Explicitly compare grp{id,mask} to zero in v4l2_device macros	2020-02-24 08:34:41 +01:00
memory
misc
net	fib: add missing attribute validation for tun_id	2020-03-18 07:14:14 +01:00
pcmcia
ras
rdma	RDMA/uverbs: Verify MR access flags	2020-02-14 16:33:23 -05:00
scsi	scsi: Revert "target: iscsi: Wait for all commands to finish before freeing a session"	2020-02-28 16:38:58 +01:00
soc
sound	ALSA: rawmidi: Avoid bit fields for state flags	2020-02-28 16:38:59 +01:00
target
trace	afs: Fix some tracing details	2020-04-02 15:28:19 +02:00
uapi	uapi: rename ext2_swab() to swab() and share globally in swab.h	2020-04-17 10:48:43 +02:00
video
xen