Eric W. Biederman 117433236a exec: Transform exec_update_mutex into a rw_semaphore ... [ Upstream commit f7cfd871ae ] Recently syzbot reported[0] that there is a deadlock amongst the users of exec_update_mutex. The problematic lock ordering found by lockdep was: perf_event_open (exec_update_mutex -> ovl_i_mutex) chown (ovl_i_mutex -> sb_writes) sendfile (sb_writes -> p->lock) by reading from a proc file and writing to overlayfs proc_pid_syscall (p->lock -> exec_update_mutex) While looking at possible solutions it occured to me that all of the users and possible users involved only wanted to state of the given process to remain the same. They are all readers. The only writer is exec. There is no reason for readers to block on each other. So fix this deadlock by transforming exec_update_mutex into a rw_semaphore named exec_update_lock that only exec takes for writing. Cc: Jann Horn <jannh@google.com> Cc: Vasiliy Kulikov <segoon@openwall.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Bernd Edlinger <bernd.edlinger@hotmail.de> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Christopher Yeoh <cyeoh@au1.ibm.com> Cc: Cyrill Gorcunov <gorcunov@gmail.com> Cc: Sargun Dhillon <sargun@sargun.me> Cc: Christian Brauner <christian.brauner@ubuntu.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Fixes: eea9673250 ("exec: Add exec_update_mutex to replace cred_guard_mutex") [0] https://lkml.kernel.org/r/00000000000063640c05ade8e3de@google.com Reported-by: syzbot+db9cdf3dd1f64252c6ef@syzkaller.appspotmail.com Link: https://lkml.kernel.org/r/87ft4mbqen.fsf@x220.int.ebiederm.org Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Sasha Levin <sashal@kernel.org>		2021-01-09 13:44:55 +01:00
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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_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
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
init_task.c	exec: Transform exec_update_mutex into a rw_semaphore	2021-01-09 13:44:55 +01:00
initramfs.c	initramfs: fix clang build failure	2020-12-30 11:51:30 +01:00
Kconfig	printk: reduce LOG_BUF_SHIFT range for H8300	2020-11-05 11:43:16 +01:00
main.c	kprobes: tracing/kprobes: Fix to kill kprobes on initmem after boot	2020-10-01 13:18:23 +02:00
Makefile	Kbuild: Handle PREEMPT_RT for version string and magic	2019-08-14 01:10:42 +09:00
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