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33a9813825
linux/fs
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Oleg Nesterov 33a9813825 introduce __next_thread(), fix next_tid() vs exec() race 
Patch series "introduce __next_thread(), change next_thread()".

After commit dce8f8ed1d ("document while_each_thread(), change
first_tid() to use for_each_thread()") + this series

1. We have only one lockless user of next_thread(), task_group_seq_get_next().
   I think it should be changed too.

2. We have only one user of task_struct->thread_group, thread_group_empty().
   The next patches will change thread_group_empty() and kill ->thread_group.


This patch (of 2):

next_tid(start) does:

	rcu_read_lock();
	if (pid_alive(start)) {
		pos = next_thread(start);
		if (thread_group_leader(pos))
			pos = NULL;
		else
			get_task_struct(pos);

it should return pos = NULL when next_thread() wraps to the 1st thread
in the thread group, group leader, and the thread_group_leader() check
tries to detect this case.

But this can race with exec. To simplify, suppose we have a main thread
M and a single sub-thread T, next_tid(T) should return NULL.

Now suppose that T execs. If next_tid(T) is called after T changes the
leadership and before it does release_task() which removes the old leader
from list, then next_thread() returns M and thread_group_leader(M) = F.

Lockless use of next_thread() should be avoided. After this change only
task_group_seq_get_next() does this, and I believe it should be changed
as well.

Link: https://lkml.kernel.org/r/20230824143112.GA31208@redhat.com
Link: https://lkml.kernel.org/r/20230824143142.GA31222@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2023-10-04 10:41:56 -07:00
..
9p - Some swap cleanups from Ma Wupeng ("fix WARN_ON in add_to_avail_list") 2023-08-29 14:25:26 -07:00
adfs for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
affs for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
afs - Some swap cleanups from Ma Wupeng ("fix WARN_ON in add_to_avail_list") 2023-08-29 14:25:26 -07:00
autofs v6.6-vfs.autofs 2023-08-28 11:39:14 -07:00
befs for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
bfs for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
btrfs for-6.6-rc3-tag 2023-09-26 09:44:08 -07:00
cachefiles - Some swap cleanups from Ma Wupeng ("fix WARN_ON in add_to_avail_list") 2023-08-29 14:25:26 -07:00
ceph ceph: remove unnecessary check for NULL in parse_longname() 2023-09-18 12:04:50 +02:00
coda v6.6-vfs.ctime 2023-08-28 09:31:32 -07:00
configfs configfs: convert to ctime accessor functions 2023-07-13 10:28:05 +02:00
cramfs v6.6-vfs.super 2023-08-28 11:04:18 -07:00
crypto
debugfs Char/Misc driver changes for 6.6-rc1 2023-09-01 09:53:54 -07:00
devpts v6.6-vfs.misc 2023-08-28 10:17:14 -07:00
dlm dlm: fix plock lookup when using multiple lockspaces 2023-08-25 10:31:39 -05:00
ecryptfs v6.6-vfs.misc 2023-08-28 10:17:14 -07:00
efivarfs efivarfs: fix statfs() on efivarfs 2023-09-11 09:10:02 +00:00
efs for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
erofs - Some swap cleanups from Ma Wupeng ("fix WARN_ON in add_to_avail_list") 2023-08-29 14:25:26 -07:00
exfat for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
exportfs exportfs: remove kernel-doc warnings in exportfs 2023-08-29 17:45:22 -04:00
ext2 \n 2023-08-30 12:10:50 -07:00
ext4 Revert "ext4: switch to multigrain timestamps" 2023-09-20 18:05:31 +02:00
f2fs f2fs update for 6.6-rc1 2023-09-02 15:37:59 -07:00
fat for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
freevxfs for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
fscache
fuse fuse update for 6.6 2023-09-05 12:45:55 -07:00
gfs2 gfs2: Fix quota=quiet oversight 2023-09-18 16:26:24 +02:00
hfs for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
hfsplus for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
hostfs hostfs: convert to ctime accessor functions 2023-07-24 10:30:00 +02:00
hpfs for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
hugetlbfs - Some swap cleanups from Ma Wupeng ("fix WARN_ON in add_to_avail_list") 2023-08-29 14:25:26 -07:00
iomap iomap: Spelling s/preceeding/preceding/g 2023-09-28 09:26:58 -07:00
isofs for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
jbd2 Regression and bug fixes for ext4. 2023-09-17 10:33:53 -07:00
jffs2 jffs2: convert to ctime accessor functions 2023-07-24 10:30:01 +02:00
jfs A few small fixes 2023-08-31 15:25:01 -07:00
kernfs Driver core changes for 6.6-rc1 2023-09-01 09:43:18 -07:00
lockd SUNRPC: Add enum svc_auth_status 2023-08-29 17:45:22 -04:00
minix for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
netfs netfs: Only call folio_start_fscache() one time for each folio 2023-09-18 12:03:46 -07:00
nfs NFSv4.1: fix zero value filehandle in post open getattr 2023-09-15 10:50:47 -04:00
nfs_common
nfsd nfsd-6.6 fixes: 2023-09-30 09:44:48 -07:00
nilfs2 nilfs2: fix potential use after free in nilfs_gccache_submit_read_data() 2023-09-29 17:20:46 -07:00
nls nls: Hide new NLS_UCS2_UTILS 2023-08-31 12:07:34 -05:00
notify dnotify: Pass argument of fcntl_dirnotify as int 2023-07-10 14:36:12 +02:00
ntfs for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
ntfs3 ntfs3: put resources during ntfs_fill_super() 2023-09-25 14:12:42 +02:00
ocfs2 ocfs2: correct range->len in ocfs2_trim_fs() 2023-10-04 10:41:56 -07:00
omfs for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
openpromfs openpromfs: convert to ctime accessor functions 2023-07-24 10:30:03 +02:00
orangefs fs: drop the timespec64 argument from update_time 2023-08-11 09:04:57 +02:00
overlayfs v6.6-rc4.vfs.fixes 2023-09-26 08:50:30 -07:00
proc introduce __next_thread(), fix next_tid() vs exec() race 2023-10-04 10:41:56 -07:00
pstore pstore fix for v6.6-rc1 2023-09-02 10:45:17 -07:00
qnx4 for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
qnx6 for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
quota \n 2023-08-30 12:10:50 -07:00
ramfs ramfs: convert to ctime accessor functions 2023-07-24 10:30:04 +02:00
reiserfs reiserfs: Replace 1-element array with C99 style flex-array 2023-09-11 14:07:46 +02:00
romfs for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
smb smb3 client fix for password freeing potential oops 2023-09-30 09:39:23 -07:00
squashfs squashfs: convert to ctime accessor functions 2023-07-24 10:30:05 +02:00
sysfs
sysv for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
tracefs eventfs: Test for dentries array allocated in eventfs_release() 2023-09-30 16:26:04 -04:00
ubifs fs: drop the timespec64 argument from update_time 2023-08-11 09:04:57 +02:00
udf \n 2023-08-30 12:10:50 -07:00
ufs for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
unicode
vboxsf v6.6-vfs.ctime 2023-08-28 09:31:32 -07:00
verity fsverity: skip PKCS#7 parser when keyring is empty 2023-08-20 10:33:43 -07:00
xfs xfs: fix reloading entire unlinked bucket lists 2023-09-24 18:12:13 -07:00
zonefs New code for 6.6: 2023-08-28 11:59:52 -07:00
aio.c aio: Annotate struct kioctx_table with __counted_by 2023-09-20 14:22:01 +02:00
anon_inodes.c
attr.c v6.6-vfs.misc 2023-08-28 10:17:14 -07:00
bad_inode.c fs: drop the timespec64 argument from update_time 2023-08-11 09:04:57 +02:00
binfmt_elf_fdpic.c fs: binfmt_elf_efpic: fix personality for ELF-FDPIC 2023-09-29 17:20:45 -07:00
binfmt_elf_test.c
binfmt_elf.c Merge branch 'expand-stack' 2023-06-28 20:35:21 -07:00
binfmt_flat.c
binfmt_misc.c fs: convert to ctime accessor functions 2023-07-13 10:28:04 +02:00
binfmt_script.c
buffer.c iomap: add a workaround for racy i_size updates on block devices 2023-09-25 08:55:00 -07:00
char_dev.c
compat_binfmt_elf.c
coredump.c v6.5/vfs.misc 2023-06-26 09:50:21 -07:00
d_path.c
dax.c mm: remove enum page_entry_size 2023-08-24 16:20:30 -07:00
dcache.c fs/dcache: Replace printk and WARN_ON by WARN 2023-08-19 13:41:11 +02:00
direct-io.c - Yosry Ahmed brought back some cgroup v1 stats in OOM logs. 2023-06-28 10:28:11 -07:00
drop_caches.c fs: drop_caches: draining pages before dropping caches 2023-08-18 10:12:11 -07:00
eventfd.c eventfd: prevent underflow for eventfd semaphores 2023-07-11 11:41:34 +02:00
eventpoll.c epoll: simplify ep_alloc() 2023-07-26 14:56:07 +02:00
exec.c - An extensive rework of kexec and crash Kconfig from Eric DeVolder 2023-08-29 14:53:51 -07:00
fcntl.c fcntl: Cast commands with int args explicitly 2023-07-10 14:36:11 +02:00
fhandle.c
file_table.c fs: use __fput_sync in close(2) 2023-08-08 19:36:51 +02:00
file.c v6.6-vfs.misc 2023-08-28 10:17:14 -07:00
filesystems.c
fs_context.c v6.6-vfs.misc 2023-08-28 10:17:14 -07:00
fs_parser.c
fs_pin.c
fs_struct.c kill do_each_thread() 2023-08-21 13:46:25 -07:00
fs_types.c
fs-writeback.c fs-writeback: do not requeue a clean inode having skipped pages 2023-09-20 14:22:01 +02:00
fsopen.c fs: add FSCONFIG_CMD_CREATE_EXCL 2023-08-14 18:48:02 +02:00
init.c
inode.c Revert "fs: add infrastructure for multigrain timestamps" 2023-09-20 18:05:31 +02:00
internal.h for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
ioctl.c v6.6-vfs.super 2023-08-28 11:04:18 -07:00
Kconfig for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
Kconfig.binfmt riscv: support the elf-fdpic binfmt loader 2023-08-23 14:17:43 -07:00
kernel_read_file.c fs: Fix kernel-doc warnings 2023-08-19 12:12:12 +02:00
libfs.c direct_write_fallback(): on error revert the ->ki_pos update from buffered write 2023-09-20 14:22:01 +02:00
locks.c NFSD 6.6 Release Notes 2023-08-31 15:32:18 -07:00
Makefile fs: add CONFIG_BUFFER_HEAD 2023-08-02 09:13:09 -06:00
mbcache.c
mnt_idmapping.c
mount.h
mpage.c
namei.c fs: Fix kernel-doc warnings 2023-08-19 12:12:12 +02:00
namespace.c v6.5/vfs.mount 2023-06-26 10:27:04 -07:00
nsfs.c fs: convert to ctime accessor functions 2023-07-13 10:28:04 +02:00
open.c v6.6-vfs.fchmodat2 2023-08-28 11:25:27 -07:00
pipe.c fs/pipe: remove duplicate "offset" initializer 2023-09-20 14:22:01 +02:00
pnode.c
pnode.h
posix_acl.c fs: convert to ctime accessor functions 2023-07-13 10:28:04 +02:00
proc_namespace.c
read_write.c fs: Fix one kernel-doc comment 2023-08-15 08:32:45 +02:00
readdir.c vfs: get rid of old '->iterate' directory operation 2023-08-06 15:08:35 +02:00
remap_range.c
select.c
seq_file.c
signalfd.c
splice.c - Some swap cleanups from Ma Wupeng ("fix WARN_ON in add_to_avail_list") 2023-08-29 14:25:26 -07:00
stack.c fs: convert to ctime accessor functions 2023-07-13 10:28:04 +02:00
stat.c Revert "fs: add infrastructure for multigrain timestamps" 2023-09-20 18:05:31 +02:00
statfs.c
super.c fs: export sget_dev() 2023-08-31 12:47:15 +02:00
sync.c
sysctls.c
timerfd.c
userfaultfd.c mm: userfaultfd: remove stale comment about core dump locking 2023-08-24 16:20:27 -07:00
utimes.c
xattr.c tmpfs,xattr: GFP_KERNEL_ACCOUNT for simple xattrs 2023-08-22 10:57:46 +02:00