Mateusz Guzik a7031f1452 kernel/fork: stop playing lockless games for exe_file replacement ... xchg originated in 6e399cd144 ("prctl: avoid using mmap_sem for exe_file serialization"). While the commit message does not explain *why* the change, I found the original submission [1] which ultimately claims it cleans things up by removing dependency of exe_file on the semaphore. However, fe69d560b5 ("kernel/fork: always deny write access to current MM exe_file") added a semaphore up/down cycle to synchronize the state of exe_file against fork, defeating the point of the original change. This is on top of semaphore trips already present both in the replacing function and prctl (the only consumer). Normally replacing exe_file does not happen for busy processes, thus write-locking is not an impediment to performance in the intended use case. If someone keeps invoking the routine for a busy processes they are trying to play dirty and that's another reason to avoid any trickery. As such I think the atomic here only adds complexity for no benefit. Just write-lock around the replacement. I also note that replacement races against the mapping check loop as nothing synchronizes actual assignment with with said checks but I am not addressing it in this patch. (Is the loop of any use to begin with?) Link: https://lore.kernel.org/linux-mm/1424979417.10344.14.camel@stgolabs.net/ [1] Link: https://lkml.kernel.org/r/20230814172140.1777161-1-mjguzik@gmail.com Signed-off-by: Mateusz Guzik <mjguzik@gmail.com> Acked-by: Oleg Nesterov <oleg@redhat.com> Acked-by: David Hildenbrand <david@redhat.com> Cc: "Christian Brauner (Microsoft)" <brauner@kernel.org> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mateusz Guzik <mjguzik@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>		2023-08-21 13:46:24 -07:00
..
9p	fs/9p: Remove unused extern declaration	2023-07-20 19:21:48 +00:00
adfs	adfs: delete unused "union adfs_dirtail" definition	2023-08-21 13:46:23 -07:00
affs	splice: Use filemap_splice_read() instead of generic_file_splice_read()	2023-05-24 08:42:17 -06:00
afs	afs: Fix accidental truncation when storing data	2023-07-04 12:24:32 -07:00
autofs	arch/*/configs/*defconfig: Replace AUTOFS4_FS by AUTOFS_FS	2023-07-29 14:08:22 -07:00
befs	befs: Replace all non-returning strlcpy with strscpy	2023-05-30 16:42:00 -07:00
bfs	splice: Use filemap_splice_read() instead of generic_file_splice_read()	2023-05-24 08:42:17 -06:00
btrfs	for-6.5-rc3-tag	2023-07-27 11:44:08 -07:00
cachefiles	v6.5/vfs.file	2023-06-26 10:14:36 -07:00
ceph	ceph: never send metrics if disable_send_metrics is set	2023-07-24 13:15:39 +02:00
coda	coda: Implement splice-read	2023-05-24 08:42:16 -06:00
configfs	fs: consolidate duplicate dt_type helpers	2023-04-03 09:23:54 +02:00
cramfs	splice: Use filemap_splice_read() instead of generic_file_splice_read()	2023-05-24 08:42:17 -06:00
crypto	fscrypt: Replace 1-element array with flexible array	2023-05-23 19:46:09 -07:00
debugfs	debugfs: Correct the 'debugfs_create_str' docs	2023-05-31 19:02:14 +01:00
devpts	devpts: simplify two-level sysctl registration for pty_kern_table	2023-03-13 12:36:34 +01:00
dlm	dlm for 6.5	2023-06-29 13:27:50 -07:00
ecryptfs	splice: Use filemap_splice_read() instead of generic_file_splice_read()	2023-05-24 08:42:17 -06:00
efivarfs	efivarfs: expose used and total size	2023-05-17 18:21:34 +02:00
efs	efs: clean up -Wunused-const-variable= warning	2023-08-18 10:18:59 -07:00
erofs	erofs: fix fsdax unavailability for chunk-based regular files	2023-07-12 00:50:56 +08:00
exfat	splice: Use filemap_splice_read() instead of generic_file_splice_read()	2023-05-24 08:42:17 -06:00
exportfs	exportfs: add explicit flag to request non-decodeable file handles	2023-05-22 18:08:37 +02:00
ext2	\n	2023-06-29 13:39:51 -07:00
ext4	ext4: fix rbtree traversal bug in ext4_mb_use_preallocated	2023-07-23 08:21:14 -04:00
f2fs	f2fs update for 6.5-rc1	2023-07-05 14:14:37 -07:00
fat	splice: Use filemap_splice_read() instead of generic_file_splice_read()	2023-05-24 08:42:17 -06:00
freevxfs	There is no particular theme here - mainly quick hits all over the tree.	2023-02-23 17:55:40 -08:00
fscache	fscache: Use clear_and_wake_up_bit() in fscache_create_volume_work()	2023-01-30 12:51:54 +00:00
fuse	fuse update for 6.5	2023-07-19 11:00:27 -07:00
gfs2	gfs2 fixes	2023-07-04 11:45:16 -07:00
hfs	splice: Use filemap_splice_read() instead of generic_file_splice_read()	2023-05-24 08:42:17 -06:00
hfsplus	fs: hfsplus: make extend error rate limited	2023-08-18 10:18:55 -07:00
hostfs	Landlock updates for v6.5-rc1	2023-06-27 17:10:27 -07:00
hpfs	splice: Use filemap_splice_read() instead of generic_file_splice_read()	2023-05-24 08:42:17 -06:00
hugetlbfs	hugetlb: revert use of page_cache_next_miss()	2023-06-23 16:59:32 -07:00
iomap	iomap: micro optimize the ki_pos assignment in iomap_file_buffered_write	2023-07-17 08:49:57 -07:00
isofs
jbd2	jbd2: remove __journal_try_to_free_buffer()	2023-07-10 23:09:21 -04:00
jffs2	for-6.5/splice-2023-06-23	2023-06-26 11:52:12 -07:00
jfs	Minor bug fixes and cleanups	2023-06-29 13:10:32 -07:00
kernfs	driver core changes for 6.5-rc1	2023-07-03 12:56:23 -07:00
lockd	NFS client updates for Linux 6.5	2023-07-01 14:38:25 -07:00
minix	splice: Use filemap_splice_read() instead of generic_file_splice_read()	2023-05-24 08:42:17 -06:00
netfs	Move netfs_extract_iter_to_sg() to lib/scatterlist.c	2023-06-08 13:42:33 +02:00
nfs	NFS client updates for Linux 6.5	2023-07-01 14:38:25 -07:00
nfs_common	NFSv4.2: remove MODULE_LICENSE in non-modules	2023-04-13 13:13:52 -07:00
nfsd	nfsd-6.5 fixes:	2023-07-25 13:54:04 -07:00
nilfs2	for-6.5/block-2023-06-23	2023-06-26 12:47:20 -07:00
nls	fs/nls: make load_nls() take a const parameter	2023-07-25 00:30:02 -05:00
notify	fanotify: disallow mount/sb marks on kernel internal pseudo fs	2023-07-04 13:29:29 +02:00
ntfs	- Yosry Ahmed brought back some cgroup v1 stats in OOM logs.	2023-06-28 10:28:11 -07:00
ntfs3	driver ntfs3 for linux 6.5	2023-07-07 14:59:38 -07:00
ocfs2	fs: ocfs2: namei: check return value of ocfs2_add_entry()	2023-08-18 10:19:00 -07:00
omfs	splice: Use filemap_splice_read() instead of generic_file_splice_read()	2023-05-24 08:42:17 -06:00
openpromfs
orangefs	orangefs: Provide a splice-read wrapper	2023-05-24 08:42:16 -06:00
overlayfs	ovl: Always reevaluate the file signature for IMA	2023-07-25 15:36:22 -07:00
proc	proc/vmcore: fix signedness bug in read_from_oldmem()	2023-07-27 13:07:05 -07:00
pstore	pstore updates for v6.5-rc1	2023-06-27 21:21:32 -07:00
qnx4	qnx4: credit contributors in CREDITS	2023-03-14 12:56:30 -06:00
qnx6	qnx6: credit contributor and mark filesystem orphan	2023-03-14 12:56:30 -06:00
quota	quota: fix warning in dqgrab()	2023-06-05 16:50:30 +02:00
ramfs	- Yosry Ahmed brought back some cgroup v1 stats in OOM logs.	2023-06-28 10:28:11 -07:00
reiserfs	- Yosry Ahmed brought back some cgroup v1 stats in OOM logs.	2023-06-28 10:28:11 -07:00
romfs	splice: Use filemap_splice_read() instead of generic_file_splice_read()	2023-05-24 08:42:17 -06:00
smb	four small client fixes	2023-07-29 20:49:13 -07:00
squashfs	squashfs: fix cache race with migration	2023-07-08 09:29:30 -07:00
sysfs	sysfs: Skip empty folders creation	2023-06-15 13:37:53 +02:00
sysv	for-6.5/splice-2023-06-23	2023-06-26 11:52:12 -07:00
tracefs	fs: port ->mkdir() to pass mnt_idmap	2023-01-19 09:24:26 +01:00
ubifs	splice: Use filemap_splice_read() instead of generic_file_splice_read()	2023-05-24 08:42:17 -06:00
udf	\n	2023-06-29 13:39:51 -07:00
ufs	splice: Use filemap_splice_read() instead of generic_file_splice_read()	2023-05-24 08:42:17 -06:00
unicode	unicode: remove MODULE_LICENSE in non-modules	2023-04-13 13:13:54 -07:00
vboxsf	hardening updates for v6.5-rc1	2023-06-27 21:24:18 -07:00
verity	fsverity: improve documentation for builtin signature support	2023-06-20 22:47:55 -07:00
xfs	xfs: convert flex-array declarations in xfs attr shortform objects	2023-07-17 08:48:56 -07:00
zonefs	- Yosry Ahmed brought back some cgroup v1 stats in OOM logs.	2023-06-28 10:28:11 -07:00
aio.c	fs/aio: Stop allocating aio rings from HIGHMEM	2023-06-15 09:22:23 +02:00
anon_inodes.c
attr.c	nfs: use vfs setgid helper	2023-03-30 08:51:48 +02:00
bad_inode.c	fs: port ->permission() to pass mnt_idmap	2023-01-19 09:24:28 +01:00
binfmt_elf_fdpic.c	binfmt: Slightly simplify elf_fdpic_map_file()	2023-05-30 15:49:46 -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	binfmt_misc: fix shift-out-of-bounds in check_special_flags	2022-12-02 13:57:04 -08:00
binfmt_script.c
buffer.c	\n	2023-06-29 13:39:51 -07:00
char_dev.c	vfs: Replace all non-returning strlcpy with strscpy	2023-05-15 09:42:01 +02:00
compat_binfmt_elf.c
coredump.c	v6.5/vfs.misc	2023-06-26 09:50:21 -07:00
d_path.c	fs: d_path: include internal.h	2023-05-17 09:16:59 +02:00
dax.c	dax: enable dax fault handler to report VM_FAULT_HWPOISON	2023-06-26 07:54:23 -06:00
dcache.c
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
eventfd.c	eventfd: show the EFD_SEMAPHORE flag in fdinfo	2023-06-15 09:22:23 +02:00
eventpoll.c	v6.5/vfs.misc	2023-06-26 09:50:21 -07:00
exec.c	kernel/fork: stop playing lockless games for exe_file replacement	2023-08-21 13:46:24 -07:00
fcntl.c	fs.idmapped.v6.3	2023-02-20 11:53:11 -08:00
fhandle.c	fsnotify: move fsnotify_open() hook into do_dentry_open()	2023-06-12 10:43:45 +02:00
file_table.c	fs: move cleanup from init_file() into its callers	2023-07-02 13:15:49 +02:00
file.c	file: always lock position for FMODE_ATOMIC_POS	2023-07-24 10:16:36 -07:00
filesystems.c
fs_context.c	fs: avoid empty option when generating legacy mount string	2023-06-07 21:49:55 +02:00
fs_parser.c	ext4: journal_path mount options should follow links	2022-12-01 10:46:54 -05:00
fs_pin.c
fs_struct.c
fs_types.c
fs-writeback.c	writeback: move wb_over_bg_thresh() call outside lock section	2023-06-09 16:25:14 -07:00
fsopen.c
init.c	fs: port ->permission() to pass mnt_idmap	2023-01-19 09:24:28 +01:00
inode.c	fs: don't assume arguments are non-NULL	2023-07-04 10:21:11 +02:00
internal.h	v6.5/vfs.file	2023-06-26 10:14:36 -07:00
ioctl.c	fs: port inode_owner_or_capable() to mnt_idmap	2023-01-19 09:24:29 +01:00
Kconfig	smb: move client and server files to common directory fs/smb	2023-05-24 16:29:21 -05:00
Kconfig.binfmt
kernel_read_file.c
libfs.c	fs: factor out a direct_write_fallback helper	2023-06-09 16:25:53 -07:00
locks.c	filelocks: use mount idmapping for setlease permission check	2023-03-09 22:36:12 +01:00
Makefile	for-6.5/block-2023-06-23	2023-06-26 12:47:20 -07:00
mbcache.c	ext4: fix deadlock due to mbcache entry corruption	2022-12-08 21:49:25 -05:00
mnt_idmapping.c	fs: move mnt_idmap	2023-01-19 09:24:30 +01:00
mount.h
mpage.c	mpage: use folios in bio end_io handler	2023-04-18 16:30:02 -07:00
namei.c	fs: no need to check source	2023-07-04 10:20:29 +02:00
namespace.c	v6.5/vfs.mount	2023-06-26 10:27:04 -07:00
nsfs.c	kill the last remaining user of proc_ns_fget()	2023-04-20 22:55:35 -04:00
open.c	\n	2023-06-29 13:31:44 -07:00
pipe.c	pipe: check for IOCB_NOWAIT alongside O_NONBLOCK	2023-05-12 17:17:27 +02:00
pnode.c	fs: allow to mount beneath top mount	2023-05-19 04:30:22 +02:00
pnode.h	fs: allow to mount beneath top mount	2023-05-19 04:30:22 +02:00
posix_acl.c	acl: don't depend on IOP_XATTR	2023-03-06 09:59:20 +01:00
proc_namespace.c	tty, proc, kernfs, random: Use copy_splice_read()	2023-05-24 08:42:16 -06:00
read_write.c	splice: Use filemap_splice_read() instead of generic_file_splice_read()	2023-05-24 08:42:17 -06:00
readdir.c	readdir: Replace one-element arrays with flexible-array members	2023-06-21 09:06:59 +02:00
remap_range.c	fs: use UB-safe check for signed addition overflow in remap_verify_area	2023-05-24 11:03:59 +02:00
select.c
seq_file.c	use less confusing names for iov_iter direction initializers	2022-11-25 13:01:55 -05:00
signalfd.c
splice.c	splice, net: Fix splice_to_socket() for O_NONBLOCK socket	2023-07-26 21:56:06 -07:00
stack.c
stat.c	fs.idmapped.v6.3	2023-02-20 11:53:11 -08:00
statfs.c	statfs: enforce statfs[64] structure initialization	2023-05-17 15:20:17 +02:00
super.c	\n	2023-06-29 13:39:51 -07:00
sync.c
sysctls.c	sysctl: Refactor base paths registrations	2023-05-23 21:43:26 -07:00
timerfd.c
userfaultfd.c	Merge mm-hotfixes-stable into mm-stable to pick up depended-upon changes.	2023-06-23 16:58:19 -07:00
utimes.c	fs.idmapped.v6.3	2023-02-20 11:53:11 -08:00
xattr.c	fs: don't call posix_acl_listxattr in generic_listxattr	2023-05-17 15:25:20 +02:00