Eric W. Biederman b796d94921 exec: Add exec_update_mutex to replace cred_guard_mutex ... [ Upstream commit eea9673250 ] The cred_guard_mutex is problematic as it is held over possibly indefinite waits for userspace. The possible indefinite waits for userspace that I have identified are: The cred_guard_mutex is held in PTRACE_EVENT_EXIT waiting for the tracer. The cred_guard_mutex is held over "put_user(0, tsk->clear_child_tid)" in exit_mm(). The cred_guard_mutex is held over "get_user(futex_offset, ...") in exit_robust_list. The cred_guard_mutex held over copy_strings. The functions get_user and put_user can trigger a page fault which can potentially wait indefinitely in the case of userfaultfd or if userspace implements part of the page fault path. In any of those cases the userspace process that the kernel is waiting for might make a different system call that winds up taking the cred_guard_mutex and result in deadlock. Holding a mutex over any of those possibly indefinite waits for userspace does not appear necessary. Add exec_update_mutex that will just cover updating the process during exec where the permissions and the objects pointed to by the task struct may be out of sync. The plan is to switch the users of cred_guard_mutex to exec_update_mutex one by one. This lets us move forward while still being careful and not introducing any regressions. Link: https://lore.kernel.org/lkml/20160921152946.GA24210@dhcp22.suse.cz/ Link: https://lore.kernel.org/lkml/AM6PR03MB5170B06F3A2B75EFB98D071AE4E60@AM6PR03MB5170.eurprd03.prod.outlook.com/ Link: https://lore.kernel.org/linux-fsdevel/20161102181806.GB1112@redhat.com/ Link: https://lore.kernel.org/lkml/20160923095031.GA14923@redhat.com/ Link: https://lore.kernel.org/lkml/20170213141452.GA30203@redhat.com/ Ref: 45c1a159b85b ("Add PTRACE_O_TRACEVFORKDONE and PTRACE_O_TRACEEXIT facilities.") Ref: 456f17cd1a28 ("[PATCH] user-vm-unlock-2.5.31-A2") Reviewed-by: Kirill Tkhai <ktkhai@virtuozzo.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Sasha Levin <sashal@kernel.org>		2020-10-01 13:17:47 +02:00
..
Kconfig	Stop the ad-hoc games with -Wno-maybe-initialized	2020-05-20 08:20:28 +02:00
Makefile	Kbuild: Handle PREEMPT_RT for version string and magic	2019-08-14 01:10:42 +09:00
calibrate.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
do_mounts.c	vfs: Convert ramfs, shmem, tmpfs, devtmpfs, rootfs to use the new mount API	2019-09-12 21:05:34 -04:00
do_mounts.h	fs: add do_mknodat() helper and ksys_mknod() wrapper; remove in-kernel calls to syscall	2018-04-02 20:15:56 +02:00
do_mounts_initrd.c	Merge branch 'mount.part1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2019-01-05 13:25:58 -08:00
do_mounts_md.c	init/: remove ineffective sparse disabling	2018-08-22 10:52:49 -07:00
do_mounts_rd.c	init/: remove ineffective sparse disabling	2018-08-22 10:52:49 -07:00
init_task.c	exec: Add exec_update_mutex to replace cred_guard_mutex	2020-10-01 13:17:47 +02:00
initramfs.c	gcc-10: mark more functions __init to avoid section mismatch warnings	2020-05-20 08:20:29 +02:00
main.c	x86: Fix early boot crash on gcc-10, third try	2020-05-20 08:20:34 +02:00
noinitramfs.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 167	2019-05-30 11:26:39 -07:00
version.c	treewide: Add SPDX license identifier for missed files	2019-05-21 10:50:45 +02:00