* Re: [PATCH v2 1/2] landlock: Serialize TSYNC thread restriction
From: Günther Noack @ 2026-02-25 12:07 UTC (permalink / raw)
To: Yihan Ding
Cc: Mickaël Salaün, Günther Noack, Paul Moore,
Jann Horn, linux-security-module, linux-kernel,
syzbot+7ea2f5e9dfd468201817
In-Reply-To: <20260225024734.3024732-2-dingyihan@uniontech.com>
On Wed, Feb 25, 2026 at 10:47:33AM +0800, Yihan Ding wrote:
> syzbot found a deadlock in landlock_restrict_sibling_threads().
> When multiple threads concurrently call landlock_restrict_self() with
> sibling thread restriction enabled, they can deadlock by mutually
> queueing task_works on each other and then blocking in kernel space
> (waiting for the other to finish).
>
> Fix this by serializing the TSYNC operations within the same process
> using the exec_update_lock. This prevents concurrent invocations
> from deadlocking. We use down_write_killable() to ensure the thread
> remains responsive to fatal signals while waiting for the lock.
>
> Fixes: 42fc7e6543f6 ("landlock: Multithreading support for landlock_restrict_self()")
> Reported-by: syzbot+7ea2f5e9dfd468201817@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=7ea2f5e9dfd468201817
> Suggested-by: Günther Noack <gnoack3000@gmail.com>
> Signed-off-by: Yihan Ding <dingyihan@uniontech.com>
> ---
> security/landlock/tsync.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/security/landlock/tsync.c b/security/landlock/tsync.c
> index de01aa899751..420fcfc2fe9a 100644
> --- a/security/landlock/tsync.c
> +++ b/security/landlock/tsync.c
> @@ -447,6 +447,13 @@ int landlock_restrict_sibling_threads(const struct cred *old_cred,
> shared_ctx.new_cred = new_cred;
> shared_ctx.set_no_new_privs = task_no_new_privs(current);
>
> + /*
> + * Serialize concurrent TSYNC operations to prevent deadlocks
> + * when multiple threads call landlock_restrict_self() simultaneously.
> + */
> + if (down_write_killable(¤t->signal->exec_update_lock))
> + return -EINTR;
> +
> /*
> * We schedule a pseudo-signal task_work for each of the calling task's
> * sibling threads. In the task work, each thread:
> @@ -556,6 +563,7 @@ int landlock_restrict_sibling_threads(const struct cred *old_cred,
> wait_for_completion(&shared_ctx.all_finished);
>
> tsync_works_release(&works);
> + up_write(¤t->signal->exec_update_lock);
>
> return atomic_read(&shared_ctx.preparation_error);
> }
> --
> 2.51.0
>
Thank you!
Reviewed-by: Günther Noack <gnoack@google.com>
^ permalink raw reply
* [PATCH v2 2/2] landlock: Clean up interrupted thread logic in TSYNC
From: Yihan Ding @ 2026-02-25 2:47 UTC (permalink / raw)
To: Mickaël Salaün, Günther Noack
Cc: Paul Moore, Jann Horn, linux-security-module, linux-kernel,
syzbot+7ea2f5e9dfd468201817, Yihan Ding
In-Reply-To: <20260225024734.3024732-1-dingyihan@uniontech.com>
In landlock_restrict_sibling_threads(), when the calling thread is
interrupted while waiting for sibling threads to prepare, it executes
a recovery path.
Previously, this path included a wait_for_completion() call on
all_prepared to prevent a Use-After-Free of the local shared_ctx.
However, this wait is redundant. Exiting the main do-while loop
already leads to a bottom cleanup section that unconditionally waits
for all_finished. Therefore, replacing the wait with a simple break
is safe, prevents UAF, and correctly unblocks the remaining task_works.
Clean up the error path by breaking the loop and updating the
surrounding comments to accurately reflect the state machine.
Suggested-by: Günther Noack <gnoack3000@gmail.com>
Signed-off-by: Yihan Ding <dingyihan@uniontech.com>
---
Changes in v2:
- Replaced wait_for_completion(&shared_ctx.all_prepared) with a break
statement based on the realization that the bottom wait for 'all_finished'
already guards against UAF.
- Updated comments for clarity.
---
security/landlock/tsync.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)
diff --git a/security/landlock/tsync.c b/security/landlock/tsync.c
index 420fcfc2fe9a..9731ec7f329a 100644
--- a/security/landlock/tsync.c
+++ b/security/landlock/tsync.c
@@ -534,24 +534,28 @@ int landlock_restrict_sibling_threads(const struct cred *old_cred,
-ERESTARTNOINTR);
/*
- * Cancel task works for tasks that did not start running yet,
- * and decrement all_prepared and num_unfinished accordingly.
+ * Opportunistic improvement: try to cancel task works
+ * for tasks that did not start running yet. We do not
+ * have a guarantee that it cancels any of the enqueued
+ * task works (because task_work_run() might already have
+ * dequeued them).
*/
cancel_tsync_works(&works, &shared_ctx);
/*
- * The remaining task works have started running, so waiting for
- * their completion will finish.
+ * Break the loop with error. The cleanup code after the loop
+ * unblocks the remaining task_works.
*/
- wait_for_completion(&shared_ctx.all_prepared);
+ break;
}
}
} while (found_more_threads &&
!atomic_read(&shared_ctx.preparation_error));
/*
- * We now have all sibling threads blocking and in "prepared" state in the
- * task work. Ask all threads to commit.
+ * We now have either (a) all sibling threads blocking and in
+ * "prepared" state in the task work, or (b) the preparation error is
+ * set. Ask all threads to commit (or abort).
*/
complete_all(&shared_ctx.ready_to_commit);
--
2.51.0
^ permalink raw reply related
* [PATCH v2 1/2] landlock: Serialize TSYNC thread restriction
From: Yihan Ding @ 2026-02-25 2:47 UTC (permalink / raw)
To: Mickaël Salaün, Günther Noack
Cc: Paul Moore, Jann Horn, linux-security-module, linux-kernel,
syzbot+7ea2f5e9dfd468201817, Yihan Ding
In-Reply-To: <20260225024734.3024732-1-dingyihan@uniontech.com>
syzbot found a deadlock in landlock_restrict_sibling_threads().
When multiple threads concurrently call landlock_restrict_self() with
sibling thread restriction enabled, they can deadlock by mutually
queueing task_works on each other and then blocking in kernel space
(waiting for the other to finish).
Fix this by serializing the TSYNC operations within the same process
using the exec_update_lock. This prevents concurrent invocations
from deadlocking. We use down_write_killable() to ensure the thread
remains responsive to fatal signals while waiting for the lock.
Fixes: 42fc7e6543f6 ("landlock: Multithreading support for landlock_restrict_self()")
Reported-by: syzbot+7ea2f5e9dfd468201817@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=7ea2f5e9dfd468201817
Suggested-by: Günther Noack <gnoack3000@gmail.com>
Signed-off-by: Yihan Ding <dingyihan@uniontech.com>
---
security/landlock/tsync.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/security/landlock/tsync.c b/security/landlock/tsync.c
index de01aa899751..420fcfc2fe9a 100644
--- a/security/landlock/tsync.c
+++ b/security/landlock/tsync.c
@@ -447,6 +447,13 @@ int landlock_restrict_sibling_threads(const struct cred *old_cred,
shared_ctx.new_cred = new_cred;
shared_ctx.set_no_new_privs = task_no_new_privs(current);
+ /*
+ * Serialize concurrent TSYNC operations to prevent deadlocks
+ * when multiple threads call landlock_restrict_self() simultaneously.
+ */
+ if (down_write_killable(¤t->signal->exec_update_lock))
+ return -EINTR;
+
/*
* We schedule a pseudo-signal task_work for each of the calling task's
* sibling threads. In the task work, each thread:
@@ -556,6 +563,7 @@ int landlock_restrict_sibling_threads(const struct cred *old_cred,
wait_for_completion(&shared_ctx.all_finished);
tsync_works_release(&works);
+ up_write(¤t->signal->exec_update_lock);
return atomic_read(&shared_ctx.preparation_error);
}
--
2.51.0
^ permalink raw reply related
* [PATCH v2 0/2] landlock: Fix TSYNC deadlock and clean up error path
From: Yihan Ding @ 2026-02-25 2:47 UTC (permalink / raw)
To: Mickaël Salaün, Günther Noack
Cc: Paul Moore, Jann Horn, linux-security-module, linux-kernel,
syzbot+7ea2f5e9dfd468201817, Yihan Ding
Hello,
This patch series fixes a deadlock in the Landlock TSYNC multithreading
support, originally reported by syzbot, and cleans up the associated
interrupt recovery path.
The deadlock occurs when multiple threads concurrently call
landlock_restrict_self() with sibling thread restriction enabled,
causing them to mutually queue task_works on each other and block
indefinitely.
* Patch 1 fixes the root cause by serializing the TSYNC operations
within the same process using the exec_update_lock.
* Patch 2 cleans up the interrupt recovery path by replacing an
unnecessary wait_for_completion() with a straightforward loop break,
avoiding Use-After-Free while unblocking remaining task_works.
Changes in v2:
- Split the changes into a 2-patch series for clearer logical separation.
- Patch 1: Adopted down_write_killable() instead of down_write() to
ensure responsiveness to fatal signals (suggested by Günther Noack).
- Patch 2: Removed wait_for_completion(&shared_ctx.all_prepared) and
replaced it with a `break`. The function's bottom wait for
'all_finished' already provides the necessary UAF protection
(suggested by Günther Noack).
Link to v1: https://lore.kernel.org/all/20260224062729.2908692-1-dingyihan@uniontech.com/
Yihan Ding (2):
landlock: Serialize TSYNC thread restriction
landlock: Clean up interrupted thread logic in TSYNC
security/landlock/tsync.c | 26 +++++++++++++++++++-------
1 file changed, 19 insertions(+), 7 deletions(-)
--
2.51.0
^ permalink raw reply
* Re: [PATCH 1/3] integrity: Make arch_ima_get_secureboot integrity-wide
From: Mimi Zohar @ 2026-02-25 0:03 UTC (permalink / raw)
To: Ard Biesheuvel
Cc: Coiby Xu, Dave Hansen, linux-integrity, Heiko Carstens,
Roberto Sassu, Catalin Marinas, Will Deacon, Madhavan Srinivasan,
Michael Ellerman, Nicholas Piggin, Christophe Leroy (CS GROUP),
Vasily Gorbik, Alexander Gordeev, Christian Borntraeger,
Sven Schnelle, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
Dave Hansen, maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT),
H. Peter Anvin, Roberto Sassu, Dmitry Kasatkin, Eric Snowberg,
Paul Moore, James Morris, Serge E. Hallyn, Jarkko Sakkinen,
moderated list:ARM64 PORT (AARCH64 ARCHITECTURE), open list,
open list:LINUX FOR POWERPC (32-BIT AND 64-BIT),
open list:S390 ARCHITECTURE,
open list:EXTENSIBLE FIRMWARE INTERFACE (EFI),
open list:SECURITY SUBSYSTEM, open list:KEYS/KEYRINGS_INTEGRITY
In-Reply-To: <CAMj1kXFBMSEdRL8FotASbQO3dcfNG0bpp9Vnm5JPn-yjyDr=GA@mail.gmail.com>
On Wed, 2026-01-21 at 17:25 +0100, Ard Biesheuvel wrote:
> On Wed, 21 Jan 2026 at 16:41, Mimi Zohar <zohar@linux.ibm.com> wrote:
> >
> > On Mon, 2026-01-19 at 12:04 +0800, Coiby Xu wrote:
> >
> > > diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
> > > index 976e75f9b9ba..5dce572192d6 100644
> > > --- a/security/integrity/ima/Kconfig
> > > +++ b/security/integrity/ima/Kconfig
> > > @@ -311,6 +311,7 @@ config IMA_QUEUE_EARLY_BOOT_KEYS
> > > config IMA_SECURE_AND_OR_TRUSTED_BOOT
> > > bool
> > > depends on IMA_ARCH_POLICY
> > > + depends on INTEGRITY_SECURE_BOOT
> > >
> > >
> > > Another idea is make a tree-wide arch_get_secureboot i.e. to move
> > > current arch_ima_get_secureboot code to arch-specific secure boot
> > > implementation. By this way, there will no need for a new Kconfig option
> > > INTEGRITY_SECURE_BOOT. But I'm not sure if there is any unforeseen
> > > concern.
> >
> > Originally basing IMA policy on the secure boot mode was an exception. As long
> > as making it public isn't an issue any longer, this sounds to me. Ard, Dave, do
> > you have any issues with replacing arch_ima_get_secureboot() with
> > arch_get_secureboot()?
>
> I don't see an issue with that. If there is a legitimate need to
> determine this even if IMA is not enabled, then this makes sense.
Ard, Dave -
FYI, Coiby posted v3 of this patch set[1], which is queued in the next-
integrity-testing branch[2].
[1]
https://lore.kernel.org/linux-integrity/20260213012851.2532722-1-coxu@redhat.com/
[2] https://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity.git/
Mimi
^ permalink raw reply
* [PATCH v3 15/15] VFS: unexport lock_rename(), lock_rename_child(), unlock_rename()
From: NeilBrown @ 2026-02-24 22:17 UTC (permalink / raw)
To: Christian Brauner, Alexander Viro, David Howells, Jan Kara,
Chuck Lever, Jeff Layton, Miklos Szeredi, Amir Goldstein,
John Johansen, Paul Moore, James Morris, Serge E. Hallyn,
Stephen Smalley, Darrick J. Wong
Cc: linux-kernel, netfs, linux-fsdevel, linux-nfs, linux-unionfs,
apparmor, linux-security-module, selinux
In-Reply-To: <20260224222542.3458677-1-neilb@ownmail.net>
From: NeilBrown <neil@brown.name>
These three function are now only used in namei.c, so they don't need to
be exported.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
---
Documentation/filesystems/porting.rst | 7 +++++++
fs/namei.c | 9 +++------
include/linux/namei.h | 3 ---
3 files changed, 10 insertions(+), 9 deletions(-)
diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst
index 1dd31ab417a2..d02aa57e4477 100644
--- a/Documentation/filesystems/porting.rst
+++ b/Documentation/filesystems/porting.rst
@@ -1368,3 +1368,10 @@ lifetime, consider using inode_set_cached_link() instead.
lookup_one_qstr_excl() is no longer exported - use start_creating() or
similar.
+---
+
+** mandatory**
+
+lock_rename(), lock_rename_child(), unlock_rename() are no
+longer available. Use start_renaming() or similar.
+
diff --git a/fs/namei.c b/fs/namei.c
index a5daa62399d7..77189335bbcc 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3775,7 +3775,7 @@ static struct dentry *lock_two_directories(struct dentry *p1, struct dentry *p2)
/*
* p1 and p2 should be directories on the same fs.
*/
-struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
+static struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
{
if (p1 == p2) {
inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
@@ -3785,12 +3785,11 @@ struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
mutex_lock(&p1->d_sb->s_vfs_rename_mutex);
return lock_two_directories(p1, p2);
}
-EXPORT_SYMBOL(lock_rename);
/*
* c1 and p2 should be on the same fs.
*/
-struct dentry *lock_rename_child(struct dentry *c1, struct dentry *p2)
+static struct dentry *lock_rename_child(struct dentry *c1, struct dentry *p2)
{
if (READ_ONCE(c1->d_parent) == p2) {
/*
@@ -3827,9 +3826,8 @@ struct dentry *lock_rename_child(struct dentry *c1, struct dentry *p2)
mutex_unlock(&c1->d_sb->s_vfs_rename_mutex);
return NULL;
}
-EXPORT_SYMBOL(lock_rename_child);
-void unlock_rename(struct dentry *p1, struct dentry *p2)
+static void unlock_rename(struct dentry *p1, struct dentry *p2)
{
inode_unlock(p1->d_inode);
if (p1 != p2) {
@@ -3837,7 +3835,6 @@ void unlock_rename(struct dentry *p1, struct dentry *p2)
mutex_unlock(&p1->d_sb->s_vfs_rename_mutex);
}
}
-EXPORT_SYMBOL(unlock_rename);
/**
* __start_renaming - lookup and lock names for rename
diff --git a/include/linux/namei.h b/include/linux/namei.h
index c7a7288cdd25..2ad6dd9987b9 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -165,9 +165,6 @@ extern int follow_down_one(struct path *);
extern int follow_down(struct path *path, unsigned int flags);
extern int follow_up(struct path *);
-extern struct dentry *lock_rename(struct dentry *, struct dentry *);
-extern struct dentry *lock_rename_child(struct dentry *, struct dentry *);
-extern void unlock_rename(struct dentry *, struct dentry *);
int start_renaming(struct renamedata *rd, int lookup_flags,
struct qstr *old_last, struct qstr *new_last);
int start_renaming_dentry(struct renamedata *rd, int lookup_flags,
--
2.50.0.107.gf914562f5916.dirty
^ permalink raw reply related
* [PATCH v3 14/15] ovl: remove ovl_lock_rename_workdir()
From: NeilBrown @ 2026-02-24 22:16 UTC (permalink / raw)
To: Christian Brauner, Alexander Viro, David Howells, Jan Kara,
Chuck Lever, Jeff Layton, Miklos Szeredi, Amir Goldstein,
John Johansen, Paul Moore, James Morris, Serge E. Hallyn,
Stephen Smalley, Darrick J. Wong
Cc: linux-kernel, netfs, linux-fsdevel, linux-nfs, linux-unionfs,
apparmor, linux-security-module, selinux
In-Reply-To: <20260224222542.3458677-1-neilb@ownmail.net>
From: NeilBrown <neil@brown.name>
This function is unused since
Commit 833d2b3a072f ("Add start_renaming_two_dentries()")
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
---
fs/overlayfs/overlayfs.h | 2 --
fs/overlayfs/util.c | 25 -------------------------
2 files changed, 27 deletions(-)
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 714a1cec3709..6fb99c583c31 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -569,8 +569,6 @@ bool ovl_is_inuse(struct dentry *dentry);
bool ovl_need_index(struct dentry *dentry);
int ovl_nlink_start(struct dentry *dentry);
void ovl_nlink_end(struct dentry *dentry);
-int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *work,
- struct dentry *upperdir, struct dentry *upper);
int ovl_check_metacopy_xattr(struct ovl_fs *ofs, const struct path *path,
struct ovl_metacopy *data);
int ovl_set_metacopy_xattr(struct ovl_fs *ofs, struct dentry *d,
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 3f1b763a8bb4..aa2a32793c2f 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -1213,31 +1213,6 @@ void ovl_nlink_end(struct dentry *dentry)
ovl_inode_unlock(inode);
}
-int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *work,
- struct dentry *upperdir, struct dentry *upper)
-{
- struct dentry *trap;
-
- /* Workdir should not be subdir of upperdir and vice versa */
- trap = lock_rename(workdir, upperdir);
- if (IS_ERR(trap))
- goto err;
- if (trap)
- goto err_unlock;
- if (work && (work->d_parent != workdir || d_unhashed(work)))
- goto err_unlock;
- if (upper && (upper->d_parent != upperdir || d_unhashed(upper)))
- goto err_unlock;
-
- return 0;
-
-err_unlock:
- unlock_rename(workdir, upperdir);
-err:
- pr_err("failed to lock workdir+upperdir\n");
- return -EIO;
-}
-
/*
* err < 0, 0 if no metacopy xattr, metacopy data size if xattr found.
* an empty xattr returns OVL_METACOPY_MIN_SIZE to distinguish from no xattr value.
--
2.50.0.107.gf914562f5916.dirty
^ permalink raw reply related
* [PATCH v3 13/15] ovl: use is_subdir() for testing if one thing is a subdir of another
From: NeilBrown @ 2026-02-24 22:16 UTC (permalink / raw)
To: Christian Brauner, Alexander Viro, David Howells, Jan Kara,
Chuck Lever, Jeff Layton, Miklos Szeredi, Amir Goldstein,
John Johansen, Paul Moore, James Morris, Serge E. Hallyn,
Stephen Smalley, Darrick J. Wong
Cc: linux-kernel, netfs, linux-fsdevel, linux-nfs, linux-unionfs,
apparmor, linux-security-module, selinux
In-Reply-To: <20260224222542.3458677-1-neilb@ownmail.net>
From: NeilBrown <neil@brown.name>
Rather than using lock_rename(), use the more obvious is_subdir() for
ensuring that neither upper nor workdir contain the other.
Also be explicit in the comment that the two directories cannot be the
same.
As this is a point-it-time sanity check and does not provide any
on-going guarantees, the removal of locking does not introduce any
interesting races.
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
---
fs/overlayfs/super.c | 15 +++++----------
1 file changed, 5 insertions(+), 10 deletions(-)
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 109643930b9f..58adefb1c5b8 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -451,18 +451,13 @@ static int ovl_lower_dir(const char *name, const struct path *path,
return 0;
}
-/* Workdir should not be subdir of upperdir and vice versa */
+/*
+ * Workdir should not be subdir of upperdir and vice versa, and
+ * they should not be the same.
+ */
static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
{
- bool ok = false;
-
- if (workdir != upperdir) {
- struct dentry *trap = lock_rename(workdir, upperdir);
- if (!IS_ERR(trap))
- unlock_rename(workdir, upperdir);
- ok = (trap == NULL);
- }
- return ok;
+ return !is_subdir(workdir, upperdir) && !is_subdir(upperdir, workdir);
}
static int ovl_setup_trap(struct super_block *sb, struct dentry *dir,
--
2.50.0.107.gf914562f5916.dirty
^ permalink raw reply related
* [PATCH v3 12/15] ovl: change ovl_create_real() to get a new lock when re-opening created file.
From: NeilBrown @ 2026-02-24 22:16 UTC (permalink / raw)
To: Christian Brauner, Alexander Viro, David Howells, Jan Kara,
Chuck Lever, Jeff Layton, Miklos Szeredi, Amir Goldstein,
John Johansen, Paul Moore, James Morris, Serge E. Hallyn,
Stephen Smalley, Darrick J. Wong
Cc: linux-kernel, netfs, linux-fsdevel, linux-nfs, linux-unionfs,
apparmor, linux-security-module, selinux
In-Reply-To: <20260224222542.3458677-1-neilb@ownmail.net>
From: NeilBrown <neil@brown.name>
When ovl_create_real() is used to create a file on the upper filesystem
it needs to return the resulting dentry - positive and hashed.
It is usually the case the that dentry passed to the create function
(e.g. vfs_create()) will be suitable but this is not guaranteed. The
filesystem may unhash that dentry forcing a repeat lookup next time the
name is wanted.
So ovl_create_real() must be (and is) aware of this and prepared to
perform that lookup to get a hash positive dentry.
This is currently done under that same directory lock that provided
exclusion for the create. Proposed changes to locking will make this
not possible - as the name, rather than the directory, will be locked.
The new APIs provided for lookup and locking do not and cannot support
this pattern.
The lock isn't needed. ovl_create_real() can drop the lock and then get
a new lock for the lookup - then check that the lookup returned the
correct inode. In a well-behaved configuration where the upper
filesystem is not being modified by a third party, this will always work
reliably, and if there are separate modification it will fail cleanly.
So change ovl_create_real() to drop the lock and call
ovl_start_creating_upper() to find the correct dentry. Note that
start_creating doesn't fail if the name already exists.
The lookup previously used the name from newdentry which was guaranteed
to be stable because the parent directory was locked. As we now drop
the lock we lose that guarantee. As newdentry is unhashed it is
unlikely for the name to change, but safest not to depend on that. So
the expected name is now passed in to ovl_create_real() and that is
used.
This removes the only remaining use of ovl_lookup_upper, so it is
removed.
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: NeilBrown <neil@brown.name>
---
fs/overlayfs/dir.c | 37 +++++++++++++++++++++++++------------
fs/overlayfs/overlayfs.h | 8 +-------
fs/overlayfs/super.c | 1 +
3 files changed, 27 insertions(+), 19 deletions(-)
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index c4feb89ad1e3..8c0a3d876fef 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -159,7 +159,8 @@ int ovl_cleanup_and_whiteout(struct ovl_fs *ofs, struct dentry *dir,
}
struct dentry *ovl_create_real(struct ovl_fs *ofs, struct dentry *parent,
- struct dentry *newdentry, struct ovl_cattr *attr)
+ struct dentry *newdentry, struct qstr *qname,
+ struct ovl_cattr *attr)
{
struct inode *dir = parent->d_inode;
int err;
@@ -221,19 +222,30 @@ struct dentry *ovl_create_real(struct ovl_fs *ofs, struct dentry *parent,
struct dentry *d;
/*
* Some filesystems (i.e. casefolded) may return an unhashed
- * negative dentry from the ovl_lookup_upper() call before
+ * negative dentry from the ovl_start_creating_upper() call before
* ovl_create_real().
* In that case, lookup again after making the newdentry
* positive, so ovl_create_upper() always returns a hashed
- * positive dentry.
+ * positive dentry. We lookup using qname which should be
+ * the same name as newentry, but is certain not to change.
+ * As we have to drop the lock before the lookup a race
+ * could result in a lookup failure. In that case we return
+ * an error.
*/
- d = ovl_lookup_upper(ofs, newdentry->d_name.name, parent,
- newdentry->d_name.len);
- dput(newdentry);
- if (IS_ERR_OR_NULL(d))
+ end_creating_keep(newdentry);
+ d = ovl_start_creating_upper(ofs, parent, qname);
+
+ if (IS_ERR_OR_NULL(d)) {
err = d ? PTR_ERR(d) : -ENOENT;
- else
+ } else if (d->d_inode != newdentry->d_inode) {
+ err = -EIO;
+ } else {
+ dput(newdentry);
return d;
+ }
+ end_creating(d);
+ dput(newdentry);
+ return ERR_PTR(err);
}
out:
if (err) {
@@ -252,7 +264,7 @@ struct dentry *ovl_create_temp(struct ovl_fs *ofs, struct dentry *workdir,
ret = ovl_start_creating_temp(ofs, workdir, name);
if (IS_ERR(ret))
return ret;
- ret = ovl_create_real(ofs, workdir, ret, attr);
+ ret = ovl_create_real(ofs, workdir, ret, &QSTR(name), attr);
return end_creating_keep(ret);
}
@@ -352,14 +364,15 @@ static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
struct dentry *newdentry;
+ struct qstr qname = QSTR_LEN(dentry->d_name.name,
+ dentry->d_name.len);
int err;
newdentry = ovl_start_creating_upper(ofs, upperdir,
- &QSTR_LEN(dentry->d_name.name,
- dentry->d_name.len));
+ &qname);
if (IS_ERR(newdentry))
return PTR_ERR(newdentry);
- newdentry = ovl_create_real(ofs, upperdir, newdentry, attr);
+ newdentry = ovl_create_real(ofs, upperdir, newdentry, &qname, attr);
if (IS_ERR(newdentry))
return PTR_ERR(newdentry);
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index cad2055ebf18..714a1cec3709 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -406,13 +406,6 @@ static inline struct file *ovl_do_tmpfile(struct ovl_fs *ofs,
return file;
}
-static inline struct dentry *ovl_lookup_upper(struct ovl_fs *ofs,
- const char *name,
- struct dentry *base, int len)
-{
- return lookup_one(ovl_upper_mnt_idmap(ofs), &QSTR_LEN(name, len), base);
-}
-
static inline struct dentry *ovl_lookup_upper_unlocked(struct ovl_fs *ofs,
const char *name,
struct dentry *base,
@@ -888,6 +881,7 @@ struct ovl_cattr {
struct dentry *ovl_create_real(struct ovl_fs *ofs,
struct dentry *parent, struct dentry *newdentry,
+ struct qstr *qname,
struct ovl_cattr *attr);
int ovl_cleanup(struct ovl_fs *ofs, struct dentry *workdir, struct dentry *dentry);
#define OVL_TEMPNAME_SIZE 20
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index d4c12feec039..109643930b9f 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -634,6 +634,7 @@ static struct dentry *ovl_lookup_or_create(struct ovl_fs *ofs,
if (!IS_ERR(child)) {
if (!child->d_inode)
child = ovl_create_real(ofs, parent, child,
+ &QSTR(name),
OVL_CATTR(mode));
end_creating_keep(child);
}
--
2.50.0.107.gf914562f5916.dirty
^ permalink raw reply related
* [PATCH v3 11/15] ovl: pass name buffer to ovl_start_creating_temp()
From: NeilBrown @ 2026-02-24 22:16 UTC (permalink / raw)
To: Christian Brauner, Alexander Viro, David Howells, Jan Kara,
Chuck Lever, Jeff Layton, Miklos Szeredi, Amir Goldstein,
John Johansen, Paul Moore, James Morris, Serge E. Hallyn,
Stephen Smalley, Darrick J. Wong
Cc: linux-kernel, netfs, linux-fsdevel, linux-nfs, linux-unionfs,
apparmor, linux-security-module, selinux
In-Reply-To: <20260224222542.3458677-1-neilb@ownmail.net>
From: NeilBrown <neil@brown.name>
Now ovl_start_creating_temp() is passed a buffer in which to store the
temp name. This will be useful in a future patch were ovl_create_real()
will need access to that name.
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: NeilBrown <neil@brown.name>
---
fs/overlayfs/dir.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index ff3dbd1ca61f..c4feb89ad1e3 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -66,10 +66,9 @@ void ovl_tempname(char name[OVL_TEMPNAME_SIZE])
}
static struct dentry *ovl_start_creating_temp(struct ovl_fs *ofs,
- struct dentry *workdir)
+ struct dentry *workdir,
+ char name[OVL_TEMPNAME_SIZE])
{
- char name[OVL_TEMPNAME_SIZE];
-
ovl_tempname(name);
return start_creating(ovl_upper_mnt_idmap(ofs), workdir,
&QSTR(name));
@@ -81,11 +80,12 @@ static struct dentry *ovl_whiteout(struct ovl_fs *ofs)
struct dentry *whiteout, *link;
struct dentry *workdir = ofs->workdir;
struct inode *wdir = workdir->d_inode;
+ char name[OVL_TEMPNAME_SIZE];
guard(mutex)(&ofs->whiteout_lock);
if (!ofs->whiteout) {
- whiteout = ovl_start_creating_temp(ofs, workdir);
+ whiteout = ovl_start_creating_temp(ofs, workdir, name);
if (IS_ERR(whiteout))
return whiteout;
err = ovl_do_whiteout(ofs, wdir, whiteout);
@@ -97,7 +97,7 @@ static struct dentry *ovl_whiteout(struct ovl_fs *ofs)
}
if (!ofs->no_shared_whiteout) {
- link = ovl_start_creating_temp(ofs, workdir);
+ link = ovl_start_creating_temp(ofs, workdir, name);
if (IS_ERR(link))
return link;
err = ovl_do_link(ofs, ofs->whiteout, wdir, link);
@@ -247,7 +247,9 @@ struct dentry *ovl_create_temp(struct ovl_fs *ofs, struct dentry *workdir,
struct ovl_cattr *attr)
{
struct dentry *ret;
- ret = ovl_start_creating_temp(ofs, workdir);
+ char name[OVL_TEMPNAME_SIZE];
+
+ ret = ovl_start_creating_temp(ofs, workdir, name);
if (IS_ERR(ret))
return ret;
ret = ovl_create_real(ofs, workdir, ret, attr);
--
2.50.0.107.gf914562f5916.dirty
^ permalink raw reply related
* [PATCH v3 10/15] cachefiles: change cachefiles_bury_object to use start_renaming_dentry()
From: NeilBrown @ 2026-02-24 22:16 UTC (permalink / raw)
To: Christian Brauner, Alexander Viro, David Howells, Jan Kara,
Chuck Lever, Jeff Layton, Miklos Szeredi, Amir Goldstein,
John Johansen, Paul Moore, James Morris, Serge E. Hallyn,
Stephen Smalley, Darrick J. Wong
Cc: linux-kernel, netfs, linux-fsdevel, linux-nfs, linux-unionfs,
apparmor, linux-security-module, selinux
In-Reply-To: <20260224222542.3458677-1-neilb@ownmail.net>
From: NeilBrown <neil@brown.name>
Rather then using lock_rename() and lookup_one() etc we can use
the new start_renaming_dentry(). This is part of centralising dir
locking and lookup so that locking rules can be changed.
Some error check are removed as not necessary. Checks for rep being a
non-dir or IS_DEADDIR and the check that ->graveyard is still a
directory only provide slightly more informative errors and have been
dropped.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
---
fs/cachefiles/namei.c | 76 ++++++++-----------------------------------
1 file changed, 14 insertions(+), 62 deletions(-)
diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index e5ec90dccc27..3af42ec78411 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -270,7 +270,8 @@ int cachefiles_bury_object(struct cachefiles_cache *cache,
struct dentry *rep,
enum fscache_why_object_killed why)
{
- struct dentry *grave, *trap;
+ struct dentry *grave;
+ struct renamedata rd = {};
struct path path, path_to_graveyard;
char nbuffer[8 + 8 + 1];
int ret;
@@ -302,77 +303,36 @@ int cachefiles_bury_object(struct cachefiles_cache *cache,
(uint32_t) ktime_get_real_seconds(),
(uint32_t) atomic_inc_return(&cache->gravecounter));
- /* do the multiway lock magic */
- trap = lock_rename(cache->graveyard, dir);
- if (IS_ERR(trap))
- return PTR_ERR(trap);
-
- /* do some checks before getting the grave dentry */
- if (rep->d_parent != dir || IS_DEADDIR(d_inode(rep))) {
- /* the entry was probably culled when we dropped the parent dir
- * lock */
- unlock_rename(cache->graveyard, dir);
- _leave(" = 0 [culled?]");
- return 0;
- }
-
- if (!d_can_lookup(cache->graveyard)) {
- unlock_rename(cache->graveyard, dir);
- cachefiles_io_error(cache, "Graveyard no longer a directory");
- return -EIO;
- }
-
- if (trap == rep) {
- unlock_rename(cache->graveyard, dir);
- cachefiles_io_error(cache, "May not make directory loop");
+ rd.mnt_idmap = &nop_mnt_idmap;
+ rd.old_parent = dir;
+ rd.new_parent = cache->graveyard;
+ rd.flags = 0;
+ ret = start_renaming_dentry(&rd, 0, rep, &QSTR(nbuffer));
+ if (ret) {
+ cachefiles_io_error(cache, "Cannot lock/lookup in graveyard");
return -EIO;
}
if (d_mountpoint(rep)) {
- unlock_rename(cache->graveyard, dir);
+ end_renaming(&rd);
cachefiles_io_error(cache, "Mountpoint in cache");
return -EIO;
}
- grave = lookup_one(&nop_mnt_idmap, &QSTR(nbuffer), cache->graveyard);
- if (IS_ERR(grave)) {
- unlock_rename(cache->graveyard, dir);
- trace_cachefiles_vfs_error(object, d_inode(cache->graveyard),
- PTR_ERR(grave),
- cachefiles_trace_lookup_error);
-
- if (PTR_ERR(grave) == -ENOMEM) {
- _leave(" = -ENOMEM");
- return -ENOMEM;
- }
-
- cachefiles_io_error(cache, "Lookup error %ld", PTR_ERR(grave));
- return -EIO;
- }
-
+ grave = rd.new_dentry;
if (d_is_positive(grave)) {
- unlock_rename(cache->graveyard, dir);
- dput(grave);
+ end_renaming(&rd);
grave = NULL;
cond_resched();
goto try_again;
}
if (d_mountpoint(grave)) {
- unlock_rename(cache->graveyard, dir);
- dput(grave);
+ end_renaming(&rd);
cachefiles_io_error(cache, "Mountpoint in graveyard");
return -EIO;
}
- /* target should not be an ancestor of source */
- if (trap == grave) {
- unlock_rename(cache->graveyard, dir);
- dput(grave);
- cachefiles_io_error(cache, "May not make directory loop");
- return -EIO;
- }
-
/* attempt the rename */
path.mnt = cache->mnt;
path.dentry = dir;
@@ -382,13 +342,6 @@ int cachefiles_bury_object(struct cachefiles_cache *cache,
if (ret < 0) {
cachefiles_io_error(cache, "Rename security error %d", ret);
} else {
- struct renamedata rd = {
- .mnt_idmap = &nop_mnt_idmap,
- .old_parent = dir,
- .old_dentry = rep,
- .new_parent = cache->graveyard,
- .new_dentry = grave,
- };
trace_cachefiles_rename(object, d_inode(rep)->i_ino, why);
ret = cachefiles_inject_read_error();
if (ret == 0)
@@ -402,8 +355,7 @@ int cachefiles_bury_object(struct cachefiles_cache *cache,
}
__cachefiles_unmark_inode_in_use(object, d_inode(rep));
- unlock_rename(cache->graveyard, dir);
- dput(grave);
+ end_renaming(&rd);
_leave(" = 0");
return 0;
}
--
2.50.0.107.gf914562f5916.dirty
^ permalink raw reply related
* [PATCH v3 09/15] ovl: Simplify ovl_lookup_real_one()
From: NeilBrown @ 2026-02-24 22:16 UTC (permalink / raw)
To: Christian Brauner, Alexander Viro, David Howells, Jan Kara,
Chuck Lever, Jeff Layton, Miklos Szeredi, Amir Goldstein,
John Johansen, Paul Moore, James Morris, Serge E. Hallyn,
Stephen Smalley, Darrick J. Wong
Cc: linux-kernel, netfs, linux-fsdevel, linux-nfs, linux-unionfs,
apparmor, linux-security-module, selinux
In-Reply-To: <20260224222542.3458677-1-neilb@ownmail.net>
From: NeilBrown <neil@brown.name>
The primary purpose of this patch is to remove the locking from
ovl_lookup_real_one() as part of centralising all locking of directories
for name operations.
The locking here isn't needed. By performing consistency tests after
the lookup we can be sure that the result of the lookup was valid at
least for a moment, which is all the original code promised.
lookup_noperm_unlocked() is used for the lookup and it will take the
lock if needed only where it is needed.
Also:
- don't take a reference to real->d_parent. The parent is
only use for a pointer comparison, and no reference is needed for
that.
- Several "if" statements have a "goto" followed by "else" - the
else isn't needed: the following statement can directly follow
the "if" as a new statement
- Use a consistent pattern of setting "err" before performing a test
and possibly going to "fail".
- remove the "out" label (now that we don't need to dput(parent) or
unlock) and simply return from fail:.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: NeilBrown <neil@brown.name>
---
fs/overlayfs/export.c | 71 ++++++++++++++++++++-----------------------
1 file changed, 33 insertions(+), 38 deletions(-)
diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
index 83f80fdb1567..896f2e9af2e2 100644
--- a/fs/overlayfs/export.c
+++ b/fs/overlayfs/export.c
@@ -349,69 +349,64 @@ static struct dentry *ovl_dentry_real_at(struct dentry *dentry, int idx)
return NULL;
}
-/*
- * Lookup a child overlay dentry to get a connected overlay dentry whose real
- * dentry is @real. If @real is on upper layer, we lookup a child overlay
- * dentry with the same name as the real dentry. Otherwise, we need to consult
- * index for lookup.
+/**
+ * ovl_lookup_real_one - Lookup a child overlay dentry to get an overlay dentry whose real dentry is given
+ * @connected: parent overlay dentry
+ * @real: given child real dentry
+ * @layer: layer in which @real exists
+ *
+ *
+ * Lookup a child overlay dentry in @connected with the same name as the @real
+ * dentry. Then check that the parent of the result is the real dentry for
+ * @connected, and @real is the real dentry for the result.
+ *
+ * Returns:
+ * %-ECHILD if the parent of @real is no longer the real dentry for @connected.
+ * %-ESTALE if @real is not the real dentry of the found dentry.
+ * Otherwise the found dentry is returned.
*/
static struct dentry *ovl_lookup_real_one(struct dentry *connected,
struct dentry *real,
const struct ovl_layer *layer)
{
- struct inode *dir = d_inode(connected);
- struct dentry *this, *parent = NULL;
+ struct dentry *this;
struct name_snapshot name;
int err;
/*
- * Lookup child overlay dentry by real name. The dir mutex protects us
- * from racing with overlay rename. If the overlay dentry that is above
- * real has already been moved to a parent that is not under the
- * connected overlay dir, we return -ECHILD and restart the lookup of
- * connected real path from the top.
- */
- inode_lock_nested(dir, I_MUTEX_PARENT);
- err = -ECHILD;
- parent = dget_parent(real);
- if (ovl_dentry_real_at(connected, layer->idx) != parent)
- goto fail;
-
- /*
- * We also need to take a snapshot of real dentry name to protect us
+ * We need to take a snapshot of real dentry name to protect us
* from racing with underlying layer rename. In this case, we don't
* care about returning ESTALE, only from dereferencing a free name
* pointer because we hold no lock on the real dentry.
*/
take_dentry_name_snapshot(&name, real);
- /*
- * No idmap handling here: it's an internal lookup.
- */
- this = lookup_noperm(&name.name, connected);
+ this = lookup_noperm_unlocked(&name.name, connected);
release_dentry_name_snapshot(&name);
+
+ err = -ECHILD;
+ if (ovl_dentry_real_at(connected, layer->idx) != real->d_parent)
+ goto fail;
+
err = PTR_ERR(this);
- if (IS_ERR(this)) {
+ if (IS_ERR(this))
goto fail;
- } else if (!this || !this->d_inode) {
- dput(this);
- err = -ENOENT;
+
+ err = -ENOENT;
+ if (!this || !this->d_inode)
goto fail;
- } else if (ovl_dentry_real_at(this, layer->idx) != real) {
- dput(this);
- err = -ESTALE;
+
+ err = -ESTALE;
+ if (ovl_dentry_real_at(this, layer->idx) != real)
goto fail;
- }
-out:
- dput(parent);
- inode_unlock(dir);
return this;
fail:
pr_warn_ratelimited("failed to lookup one by real (%pd2, layer=%d, connected=%pd2, err=%i)\n",
real, layer->idx, connected, err);
- this = ERR_PTR(err);
- goto out;
+ if (!IS_ERR(this))
+ dput(this);
+ return ERR_PTR(err);
}
static struct dentry *ovl_lookup_real(struct super_block *sb,
--
2.50.0.107.gf914562f5916.dirty
^ permalink raw reply related
* [PATCH v3 08/15] VFS: make lookup_one_qstr_excl() static.
From: NeilBrown @ 2026-02-24 22:16 UTC (permalink / raw)
To: Christian Brauner, Alexander Viro, David Howells, Jan Kara,
Chuck Lever, Jeff Layton, Miklos Szeredi, Amir Goldstein,
John Johansen, Paul Moore, James Morris, Serge E. Hallyn,
Stephen Smalley, Darrick J. Wong
Cc: linux-kernel, netfs, linux-fsdevel, linux-nfs, linux-unionfs,
apparmor, linux-security-module, selinux
In-Reply-To: <20260224222542.3458677-1-neilb@ownmail.net>
From: NeilBrown <neil@brown.name>
lookup_one_qstr_excl() is no longer used outside of namei.c, so
make it static.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
---
Documentation/filesystems/porting.rst | 7 +++++++
fs/namei.c | 5 ++---
include/linux/namei.h | 3 ---
3 files changed, 9 insertions(+), 6 deletions(-)
diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst
index 52ff1d19405b..1dd31ab417a2 100644
--- a/Documentation/filesystems/porting.rst
+++ b/Documentation/filesystems/porting.rst
@@ -1361,3 +1361,10 @@ to match what strlen() would return if it was ran on the string.
However, if the string is freely accessible for the duration of inode's
lifetime, consider using inode_set_cached_link() instead.
+
+---
+
+**mandatory**
+
+lookup_one_qstr_excl() is no longer exported - use start_creating() or
+similar.
diff --git a/fs/namei.c b/fs/namei.c
index 11c9a4a6c396..a5daa62399d7 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1782,8 +1782,8 @@ static struct dentry *lookup_dcache(const struct qstr *name,
* Will return -ENOENT if name isn't found and LOOKUP_CREATE wasn't passed.
* Will return -EEXIST if name is found and LOOKUP_EXCL was passed.
*/
-struct dentry *lookup_one_qstr_excl(const struct qstr *name,
- struct dentry *base, unsigned int flags)
+static struct dentry *lookup_one_qstr_excl(const struct qstr *name,
+ struct dentry *base, unsigned int flags)
{
struct dentry *dentry;
struct dentry *old;
@@ -1820,7 +1820,6 @@ struct dentry *lookup_one_qstr_excl(const struct qstr *name,
}
return dentry;
}
-EXPORT_SYMBOL(lookup_one_qstr_excl);
/**
* lookup_fast - do fast lockless (but racy) lookup of a dentry
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 58600cf234bc..c7a7288cdd25 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -54,9 +54,6 @@ extern int path_pts(struct path *path);
extern int user_path_at(int, const char __user *, unsigned, struct path *);
-struct dentry *lookup_one_qstr_excl(const struct qstr *name,
- struct dentry *base,
- unsigned int flags);
extern int kern_path(const char *, unsigned, struct path *);
struct dentry *kern_path_parent(const char *name, struct path *parent);
--
2.50.0.107.gf914562f5916.dirty
^ permalink raw reply related
* [PATCH v3 07/15] nfsd: switch purge_old() to use start_removing_noperm()
From: NeilBrown @ 2026-02-24 22:16 UTC (permalink / raw)
To: Christian Brauner, Alexander Viro, David Howells, Jan Kara,
Chuck Lever, Jeff Layton, Miklos Szeredi, Amir Goldstein,
John Johansen, Paul Moore, James Morris, Serge E. Hallyn,
Stephen Smalley, Darrick J. Wong
Cc: linux-kernel, netfs, linux-fsdevel, linux-nfs, linux-unionfs,
apparmor, linux-security-module, selinux
In-Reply-To: <20260224222542.3458677-1-neilb@ownmail.net>
From: NeilBrown <neil@brown.name>
Rather than explicit locking, use the start_removing_noperm() and
end_removing() wrappers.
This was not done with other start_removing changes due to conflicting
in-flight patches.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
---
fs/nfsd/nfs4recover.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
index b4bf85f96f6e..b338473d6e52 100644
--- a/fs/nfsd/nfs4recover.c
+++ b/fs/nfsd/nfs4recover.c
@@ -352,16 +352,14 @@ purge_old(struct dentry *parent, char *cname, struct nfsd_net *nn)
if (nfs4_has_reclaimed_state(name, nn))
goto out_free;
- inode_lock_nested(d_inode(parent), I_MUTEX_PARENT);
- child = lookup_one(&nop_mnt_idmap, &QSTR(cname), parent);
+ child = start_removing_noperm(parent, &QSTR(cname));
if (!IS_ERR(child)) {
status = vfs_rmdir(&nop_mnt_idmap, d_inode(parent), child, NULL);
if (status)
printk("failed to remove client recovery directory %pd\n",
child);
- dput(child);
}
- inode_unlock(d_inode(parent));
+ end_removing(child);
out_free:
kfree(name.data);
--
2.50.0.107.gf914562f5916.dirty
^ permalink raw reply related
* [PATCH v3 06/15] selinux: Use simple_start_creating() / simple_done_creating()
From: NeilBrown @ 2026-02-24 22:16 UTC (permalink / raw)
To: Christian Brauner, Alexander Viro, David Howells, Jan Kara,
Chuck Lever, Jeff Layton, Miklos Szeredi, Amir Goldstein,
John Johansen, Paul Moore, James Morris, Serge E. Hallyn,
Stephen Smalley, Darrick J. Wong
Cc: linux-kernel, netfs, linux-fsdevel, linux-nfs, linux-unionfs,
apparmor, linux-security-module, selinux
In-Reply-To: <20260224222542.3458677-1-neilb@ownmail.net>
From: NeilBrown <neil@brown.name>
Instead of explicitly locking the parent and performing a lookup in
selinux, use simple_start_creating(), and then use
simple_done_creating() to unlock.
This extends the region that the directory is locked for, and also
performs a lookup.
The lock extension is of no real consequence.
The lookup uses simple_lookup() and so always succeeds. Thus when
d_make_persistent() is called the dentry will already be hashed.
d_make_persistent() handles this case.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: NeilBrown <neil@brown.name>
---
security/selinux/selinuxfs.c | 17 ++++++++---------
1 file changed, 8 insertions(+), 9 deletions(-)
diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 3245cc531555..83aa765a09f9 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -1931,27 +1931,26 @@ static const struct inode_operations swapover_dir_inode_operations = {
static struct dentry *sel_make_swapover_dir(struct super_block *sb,
unsigned long *ino)
{
- struct dentry *dentry = d_alloc_name(sb->s_root, ".swapover");
+ struct dentry *dentry;
struct inode *inode;
- if (!dentry)
- return ERR_PTR(-ENOMEM);
-
inode = sel_make_inode(sb, S_IFDIR);
- if (!inode) {
- dput(dentry);
+ if (!inode)
return ERR_PTR(-ENOMEM);
+
+ dentry = simple_start_creating(sb->s_root, ".swapover");
+ if (IS_ERR(dentry)) {
+ iput(inode);
+ return dentry;
}
inode->i_op = &swapover_dir_inode_operations;
inode->i_ino = ++(*ino);
/* directory inodes start off with i_nlink == 2 (for "." entry) */
inc_nlink(inode);
- inode_lock(sb->s_root->d_inode);
d_make_persistent(dentry, inode);
inc_nlink(sb->s_root->d_inode);
- inode_unlock(sb->s_root->d_inode);
- dput(dentry);
+ simple_done_creating(dentry);
return dentry; // borrowed
}
--
2.50.0.107.gf914562f5916.dirty
^ permalink raw reply related
* [PATCH v3 05/15] Apparmor: Use simple_start_creating() / simple_done_creating()
From: NeilBrown @ 2026-02-24 22:16 UTC (permalink / raw)
To: Christian Brauner, Alexander Viro, David Howells, Jan Kara,
Chuck Lever, Jeff Layton, Miklos Szeredi, Amir Goldstein,
John Johansen, Paul Moore, James Morris, Serge E. Hallyn,
Stephen Smalley, Darrick J. Wong
Cc: linux-kernel, netfs, linux-fsdevel, linux-nfs, linux-unionfs,
apparmor, linux-security-module, selinux
In-Reply-To: <20260224222542.3458677-1-neilb@ownmail.net>
From: NeilBrown <neil@brown.name>
Instead of explicitly locking the parent and performing a look up in
apparmor, use simple_start_creating(), and then simple_done_creating()
to unlock and drop the dentry.
This removes the need to check for an existing entry (as
simple_start_creating() acts like an exclusive create and can return
-EEXIST), simplifies error paths, and keeps dir locking code
centralised.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
---
security/apparmor/apparmorfs.c | 35 ++++++++--------------------------
1 file changed, 8 insertions(+), 27 deletions(-)
diff --git a/security/apparmor/apparmorfs.c b/security/apparmor/apparmorfs.c
index 2f84bd23edb6..f93c4f31d02a 100644
--- a/security/apparmor/apparmorfs.c
+++ b/security/apparmor/apparmorfs.c
@@ -282,32 +282,20 @@ static struct dentry *aafs_create(const char *name, umode_t mode,
dir = d_inode(parent);
- inode_lock(dir);
- dentry = lookup_noperm(&QSTR(name), parent);
+ dentry = simple_start_creating(parent, name);
if (IS_ERR(dentry)) {
error = PTR_ERR(dentry);
- goto fail_lock;
- }
-
- if (d_really_is_positive(dentry)) {
- error = -EEXIST;
- goto fail_dentry;
+ goto fail;
}
error = __aafs_setup_d_inode(dir, dentry, mode, data, link, fops, iops);
+ simple_done_creating(dentry);
if (error)
- goto fail_dentry;
- inode_unlock(dir);
-
+ goto fail;
return dentry;
-fail_dentry:
- dput(dentry);
-
-fail_lock:
- inode_unlock(dir);
+fail:
simple_release_fs(&aafs_mnt, &aafs_count);
-
return ERR_PTR(error);
}
@@ -2585,8 +2573,7 @@ static int aa_mk_null_file(struct dentry *parent)
if (error)
return error;
- inode_lock(d_inode(parent));
- dentry = lookup_noperm(&QSTR(NULL_FILE_NAME), parent);
+ dentry = simple_start_creating(parent, NULL_FILE_NAME);
if (IS_ERR(dentry)) {
error = PTR_ERR(dentry);
goto out;
@@ -2594,7 +2581,7 @@ static int aa_mk_null_file(struct dentry *parent)
inode = new_inode(parent->d_inode->i_sb);
if (!inode) {
error = -ENOMEM;
- goto out1;
+ goto out;
}
inode->i_ino = get_next_ino();
@@ -2606,18 +2593,12 @@ static int aa_mk_null_file(struct dentry *parent)
aa_null.dentry = dget(dentry);
aa_null.mnt = mntget(mount);
- error = 0;
-
-out1:
- dput(dentry);
out:
- inode_unlock(d_inode(parent));
+ simple_done_creating(dentry);
simple_release_fs(&mount, &count);
return error;
}
-
-
static const char *policy_get_link(struct dentry *dentry,
struct inode *inode,
struct delayed_call *done)
--
2.50.0.107.gf914562f5916.dirty
^ permalink raw reply related
* [PATCH v3 04/15] libfs: change simple_done_creating() to use end_creating()
From: NeilBrown @ 2026-02-24 22:16 UTC (permalink / raw)
To: Christian Brauner, Alexander Viro, David Howells, Jan Kara,
Chuck Lever, Jeff Layton, Miklos Szeredi, Amir Goldstein,
John Johansen, Paul Moore, James Morris, Serge E. Hallyn,
Stephen Smalley, Darrick J. Wong
Cc: linux-kernel, netfs, linux-fsdevel, linux-nfs, linux-unionfs,
apparmor, linux-security-module, selinux
In-Reply-To: <20260224222542.3458677-1-neilb@ownmail.net>
From: NeilBrown <neil@brown.name>
simple_done_creating() and end_creating() are identical.
So change the former to use the latter. This further centralises
unlocking of directories.
Signed-off-by: NeilBrown <neil@brown.name>
---
fs/libfs.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/fs/libfs.c b/fs/libfs.c
index 74134ba2e8d1..63b4fb082435 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -2318,7 +2318,6 @@ EXPORT_SYMBOL(simple_start_creating);
/* parent must have been held exclusive since simple_start_creating() */
void simple_done_creating(struct dentry *child)
{
- inode_unlock(child->d_parent->d_inode);
- dput(child);
+ end_creating(child);
}
EXPORT_SYMBOL(simple_done_creating);
--
2.50.0.107.gf914562f5916.dirty
^ permalink raw reply related
* [PATCH v3 03/15] VFS: move the start_dirop() kerndoc comment to before start_dirop()
From: NeilBrown @ 2026-02-24 22:16 UTC (permalink / raw)
To: Christian Brauner, Alexander Viro, David Howells, Jan Kara,
Chuck Lever, Jeff Layton, Miklos Szeredi, Amir Goldstein,
John Johansen, Paul Moore, James Morris, Serge E. Hallyn,
Stephen Smalley, Darrick J. Wong
Cc: linux-kernel, netfs, linux-fsdevel, linux-nfs, linux-unionfs,
apparmor, linux-security-module, selinux
In-Reply-To: <20260224222542.3458677-1-neilb@ownmail.net>
From: NeilBrown <neil@brown.name>
This kerneldoc comment was always meant for start_dirop(), not for
__start_dirop() which is a static function and doesn't need
documentation.
It was in the wrong place and was then incorrectly renamed (instead of
moved) and useless "documentation" was added for "@state" was provided.
This patch reverts the name, removes the mention of @state, and moves
the comment to where it belongs.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
---
fs/namei.c | 27 +++++++++++++--------------
1 file changed, 13 insertions(+), 14 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index 6f595f58acfe..11c9a4a6c396 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2893,20 +2893,6 @@ static int filename_parentat(int dfd, struct filename *name,
return __filename_parentat(dfd, name, flags, parent, last, type, NULL);
}
-/**
- * __start_dirop - begin a create or remove dirop, performing locking and lookup
- * @parent: the dentry of the parent in which the operation will occur
- * @name: a qstr holding the name within that parent
- * @lookup_flags: intent and other lookup flags.
- * @state: task state bitmask
- *
- * The lookup is performed and necessary locks are taken so that, on success,
- * the returned dentry can be operated on safely.
- * The qstr must already have the hash value calculated.
- *
- * Returns: a locked dentry, or an error.
- *
- */
static struct dentry *__start_dirop(struct dentry *parent, struct qstr *name,
unsigned int lookup_flags,
unsigned int state)
@@ -2928,6 +2914,19 @@ static struct dentry *__start_dirop(struct dentry *parent, struct qstr *name,
return dentry;
}
+/**
+ * start_dirop - begin a create or remove dirop, performing locking and lookup
+ * @parent: the dentry of the parent in which the operation will occur
+ * @name: a qstr holding the name within that parent
+ * @lookup_flags: intent and other lookup flags.
+ *
+ * The lookup is performed and necessary locks are taken so that, on success,
+ * the returned dentry can be operated on safely.
+ * The qstr must already have the hash value calculated.
+ *
+ * Returns: a locked dentry, or an error.
+ *
+ */
struct dentry *start_dirop(struct dentry *parent, struct qstr *name,
unsigned int lookup_flags)
{
--
2.50.0.107.gf914562f5916.dirty
^ permalink raw reply related
* [PATCH v3 02/15] fs/proc: Don't lock root inode when creating "self" and "thread-self"
From: NeilBrown @ 2026-02-24 22:16 UTC (permalink / raw)
To: Christian Brauner, Alexander Viro, David Howells, Jan Kara,
Chuck Lever, Jeff Layton, Miklos Szeredi, Amir Goldstein,
John Johansen, Paul Moore, James Morris, Serge E. Hallyn,
Stephen Smalley, Darrick J. Wong
Cc: linux-kernel, netfs, linux-fsdevel, linux-nfs, linux-unionfs,
apparmor, linux-security-module, selinux
In-Reply-To: <20260224222542.3458677-1-neilb@ownmail.net>
From: NeilBrown <neil@brown.name>
proc_setup_self() and proc_setup_thread_self() are only called from
proc_fill_super() which is before the filesystem is "live". So there is
no need to lock the root directory when adding "self" and "thread-self".
This is clear from simple_fill_super() which provides similar
functionality for other filesystems and does not lock anything.
The locking is not harmful, except that it may be confusing to a reader.
As part of an effort to centralise all locking for directories for
name-based operations (prior to changing some locking rules), it is
simplest to remove the locking here.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
---
fs/proc/self.c | 3 ---
fs/proc/thread_self.c | 3 ---
2 files changed, 6 deletions(-)
diff --git a/fs/proc/self.c b/fs/proc/self.c
index 62d2c0cfe35c..56adf1c68f7a 100644
--- a/fs/proc/self.c
+++ b/fs/proc/self.c
@@ -35,11 +35,9 @@ unsigned self_inum __ro_after_init;
int proc_setup_self(struct super_block *s)
{
- struct inode *root_inode = d_inode(s->s_root);
struct dentry *self;
int ret = -ENOMEM;
- inode_lock(root_inode);
self = d_alloc_name(s->s_root, "self");
if (self) {
struct inode *inode = new_inode(s);
@@ -55,7 +53,6 @@ int proc_setup_self(struct super_block *s)
}
dput(self);
}
- inode_unlock(root_inode);
if (ret)
pr_err("proc_fill_super: can't allocate /proc/self\n");
diff --git a/fs/proc/thread_self.c b/fs/proc/thread_self.c
index d6113dbe58e0..61ac62c3fd9f 100644
--- a/fs/proc/thread_self.c
+++ b/fs/proc/thread_self.c
@@ -35,11 +35,9 @@ unsigned thread_self_inum __ro_after_init;
int proc_setup_thread_self(struct super_block *s)
{
- struct inode *root_inode = d_inode(s->s_root);
struct dentry *thread_self;
int ret = -ENOMEM;
- inode_lock(root_inode);
thread_self = d_alloc_name(s->s_root, "thread-self");
if (thread_self) {
struct inode *inode = new_inode(s);
@@ -55,7 +53,6 @@ int proc_setup_thread_self(struct super_block *s)
}
dput(thread_self);
}
- inode_unlock(root_inode);
if (ret)
pr_err("proc_fill_super: can't allocate /proc/thread-self\n");
--
2.50.0.107.gf914562f5916.dirty
^ permalink raw reply related
* [PATCH v3 01/15] VFS: note error returns in documentation for various lookup functions
From: NeilBrown @ 2026-02-24 22:16 UTC (permalink / raw)
To: Christian Brauner, Alexander Viro, David Howells, Jan Kara,
Chuck Lever, Jeff Layton, Miklos Szeredi, Amir Goldstein,
John Johansen, Paul Moore, James Morris, Serge E. Hallyn,
Stephen Smalley, Darrick J. Wong
Cc: linux-kernel, netfs, linux-fsdevel, linux-nfs, linux-unionfs,
apparmor, linux-security-module, selinux
In-Reply-To: <20260224222542.3458677-1-neilb@ownmail.net>
From: NeilBrown <neil@brown.name>
Darrick recently noted that try_lookup_noperm() is documented as
"Look up a dentry by name in the dcache, returning NULL if it does not
currently exist." but it can in fact return an error.
So update the documentation for that and related functions.
Link: https://lore.kernel.org/all/20260218234917.GA6490@frogsfrogsfrogs/
Cc: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
---
fs/namei.c | 29 ++++++++++++++++++++++++++++-
1 file changed, 28 insertions(+), 1 deletion(-)
diff --git a/fs/namei.c b/fs/namei.c
index 58f715f7657e..6f595f58acfe 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3124,7 +3124,8 @@ static int lookup_one_common(struct mnt_idmap *idmap,
* @base: base directory to lookup from
*
* Look up a dentry by name in the dcache, returning NULL if it does not
- * currently exist. The function does not try to create a dentry and if one
+ * currently exist or an error if there is a problem with the name.
+ * The function does not try to create a dentry and if one
* is found it doesn't try to revalidate it.
*
* Note that this routine is purely a helper for filesystem usage and should
@@ -3132,6 +3133,11 @@ static int lookup_one_common(struct mnt_idmap *idmap,
*
* No locks need be held - only a counted reference to @base is needed.
*
+ * Returns:
+ * - ref-counted dentry on success, or
+ * - %NULL if name could not be found, or
+ * - ERR_PTR(-EACCES) if name is dot or dotdot or contains a slash or nul, or
+ * - ERR_PTR() if fs provide ->d_hash, and this returned an error.
*/
struct dentry *try_lookup_noperm(struct qstr *name, struct dentry *base)
{
@@ -3208,6 +3214,11 @@ EXPORT_SYMBOL(lookup_one);
*
* Unlike lookup_one, it should be called without the parent
* i_rwsem held, and will take the i_rwsem itself if necessary.
+ *
+ * Returns: - A dentry, possibly negative, or
+ * - same errors as try_lookup_noperm() or
+ * - ERR_PTR(-ENOENT) if parent has been removed, or
+ * - ERR_PTR(-EACCES) if parent directory is not searchable.
*/
struct dentry *lookup_one_unlocked(struct mnt_idmap *idmap, struct qstr *name,
struct dentry *base)
@@ -3244,6 +3255,10 @@ EXPORT_SYMBOL(lookup_one_unlocked);
* It should be called without the parent i_rwsem held, and will take
* the i_rwsem itself if necessary. If a fatal signal is pending or
* delivered, it will return %-EINTR if the lock is needed.
+ *
+ * Returns: A dentry, possibly negative, or
+ * - same errors as lookup_one_unlocked() or
+ * - ERR_PTR(-EINTR) if a fatal signal is pending.
*/
struct dentry *lookup_one_positive_killable(struct mnt_idmap *idmap,
struct qstr *name,
@@ -3283,6 +3298,10 @@ EXPORT_SYMBOL(lookup_one_positive_killable);
* This can be used for in-kernel filesystem clients such as file servers.
*
* The helper should be called without i_rwsem held.
+ *
+ * Returns: A positive dentry, or
+ * - ERR_PTR(-ENOENT) if the name could not be found, or
+ * - same errors as lookup_one_unlocked().
*/
struct dentry *lookup_one_positive_unlocked(struct mnt_idmap *idmap,
struct qstr *name,
@@ -3311,6 +3330,10 @@ EXPORT_SYMBOL(lookup_one_positive_unlocked);
*
* Unlike try_lookup_noperm() it *does* revalidate the dentry if it already
* existed.
+ *
+ * Returns: A dentry, possibly negative, or
+ * - ERR_PTR(-ENOENT) if parent has been removed, or
+ * - same errors as try_lookup_noperm()
*/
struct dentry *lookup_noperm_unlocked(struct qstr *name, struct dentry *base)
{
@@ -3335,6 +3358,10 @@ EXPORT_SYMBOL(lookup_noperm_unlocked);
* _can_ become positive at any time, so callers of lookup_noperm_unlocked()
* need to be very careful; pinned positives have ->d_inode stable, so
* this one avoids such problems.
+ *
+ * Returns: A positive dentry, or
+ * - ERR_PTR(-ENOENT) if name cannot be found or parent has been removed, or
+ * - same errors as try_lookup_noperm()
*/
struct dentry *lookup_noperm_positive_unlocked(struct qstr *name,
struct dentry *base)
--
2.50.0.107.gf914562f5916.dirty
^ permalink raw reply related
* [PATCH v3 00/15] Further centralising of directory locking for name ops.
From: NeilBrown @ 2026-02-24 22:16 UTC (permalink / raw)
To: Christian Brauner, Alexander Viro, David Howells, Jan Kara,
Chuck Lever, Jeff Layton, Miklos Szeredi, Amir Goldstein,
John Johansen, Paul Moore, James Morris, Serge E. Hallyn,
Stephen Smalley, Darrick J. Wong
Cc: linux-kernel, netfs, linux-fsdevel, linux-nfs, linux-unionfs,
apparmor, linux-security-module, selinux
Following Chris Mason's tool-based review, here is v3 with some fixes.
Particularly 06/15 mistakenly tested the result of start_creating for NULL
and 09/15 had some really messed up flow in error handling.
Also human-language typos fixed.
This code is in
github.com:neilbrown/linux.git
branch pdirops
For anyone interested, my next batch is in branch pdirops-next
Original patch description below.
Thanks,
NeilBrown
I am working towards changing the locking rules for name-operations: locking
the name rather than the whole directory.
The current part of this process is centralising all the locking so that
it can be changed in one place.
Recently "start_creating", "start_removing", "start_renaming" and related
interaces were added which combine the locking and the lookup. At that time
many callers were changed to use the new interfaces. However there are still
an assortment of places out side of fs/namei.c where the directory is locked
explictly, whether with inode_lock() or lock_rename() or similar. These were
missed in the first pass for an assortment of uninteresting reasons.
This series addresses the remaining places where explicit locking is
used, and changes them to use the new interfaces, or otherwise removes
the explicit locking.
The biggest changes are in overlayfs. The other changes are quite
simple, though maybe the cachefiles changes is the least simple of those.
I'm running the --overlay tests in xfstests and nothing has popped yet.
I'll continue with this and run some NFS tests too.
Thanks for your review of these patches!
NeilBrown
[PATCH v3 01/15] VFS: note error returns in documentation for various
[PATCH v3 02/15] fs/proc: Don't lock root inode when creating "self"
[PATCH v3 03/15] VFS: move the start_dirop() kerndoc comment to
[PATCH v3 04/15] libfs: change simple_done_creating() to use
[PATCH v3 05/15] Apparmor: Use simple_start_creating() /
[PATCH v3 06/15] selinux: Use simple_start_creating() /
[PATCH v3 07/15] nfsd: switch purge_old() to use
[PATCH v3 08/15] VFS: make lookup_one_qstr_excl() static.
[PATCH v3 09/15] ovl: Simplify ovl_lookup_real_one()
[PATCH v3 10/15] cachefiles: change cachefiles_bury_object to use
[PATCH v3 11/15] ovl: pass name buffer to ovl_start_creating_temp()
[PATCH v3 12/15] ovl: change ovl_create_real() to get a new lock when
[PATCH v3 13/15] ovl: use is_subdir() for testing if one thing is a
[PATCH v3 14/15] ovl: remove ovl_lock_rename_workdir()
[PATCH v3 15/15] VFS: unexport lock_rename(), lock_rename_child(),
^ permalink raw reply
* Re: [PATCH] lsm: move inode IS_PRIVATE checks to individual LSMs
From: Paul Moore @ 2026-02-24 19:12 UTC (permalink / raw)
To: Stephen Smalley
Cc: Casey Schaufler, danieldurning.work, linux-security-module,
selinux, linux-integrity, jmorris, serge, john.johansen, zohar,
roberto.sassu, dmitry.kasatkin, mic, takedakn, penguin-kernel
In-Reply-To: <CAEjxPJ79V7hM=VnbB1dVA96jjr1yeN9qsLjXb4ALv1VmcRfJ-A@mail.gmail.com>
On Tue, Feb 24, 2026 at 9:44 AM Stephen Smalley
<stephen.smalley.work@gmail.com> wrote:
> On Mon, Feb 23, 2026 at 5:21 PM Paul Moore <paul@paul-moore.com> wrote:
> > I'm not going to argue with that, and perhaps that is a good next
> > step: send a quick RFC patch to the VFS folks, with the LSM list CC'd,
> > that drops setting the S_PRIVATE flag to see if they complain too
> > loudly. Based on other threads, Christian is aware that we are
> > starting to look at better/proper handling of pidfds/pidfs so he may
> > be open to dropping S_PRIVATE since it doesn't really have much impact
> > outside of the LSM, but who knows; the VFS folks have been growing a
> > bit more anti-LSM as of late.
>
> Adding S_PRIVATE to pidfs inodes was originally motivated by this bug report:
> https://lore.kernel.org/linux-fsdevel/20240222190334.GA412503@dev-arch.thelio-3990X/
> when pidfs was first introduced as its own distinct filesystem type.
> Otherwise, Fedora (and likely any other system enforcing SELinux)
> stopped working.
> So we can't unconditionally remove S_PRIVATE from pidfs inodes without breaking
> existing userspace/policy. If we want to introduce controls over pidfs
> inodes and do so in a
> backward-compatible manner, we have to either move the S_PRIVATE
> handling into the
> individual LSMs ...
... just like was originally proposed. Just do that and be done with
it; back-n-forth like this just wastes time and energy.
--
paul-moore.com
^ permalink raw reply
* Re: [PATCH] lsm: move inode IS_PRIVATE checks to individual LSMs
From: Casey Schaufler @ 2026-02-24 18:21 UTC (permalink / raw)
To: Stephen Smalley, Paul Moore
Cc: danieldurning.work, linux-security-module, selinux,
linux-integrity, jmorris, serge, john.johansen, zohar,
roberto.sassu, dmitry.kasatkin, mic, takedakn, penguin-kernel,
Casey Schaufler
In-Reply-To: <CAEjxPJ79V7hM=VnbB1dVA96jjr1yeN9qsLjXb4ALv1VmcRfJ-A@mail.gmail.com>
On 2/24/2026 6:44 AM, Stephen Smalley wrote:
> On Mon, Feb 23, 2026 at 5:21 PM Paul Moore <paul@paul-moore.com> wrote:
>> I'm not going to argue with that, and perhaps that is a good next
>> step: send a quick RFC patch to the VFS folks, with the LSM list CC'd,
>> that drops setting the S_PRIVATE flag to see if they complain too
>> loudly. Based on other threads, Christian is aware that we are
>> starting to look at better/proper handling of pidfds/pidfs so he may
>> be open to dropping S_PRIVATE since it doesn't really have much impact
>> outside of the LSM, but who knows; the VFS folks have been growing a
>> bit more anti-LSM as of late.
> Adding S_PRIVATE to pidfs inodes was originally motivated by this bug report:
> https://lore.kernel.org/linux-fsdevel/20240222190334.GA412503@dev-arch.thelio-3990X/
> when pidfs was first introduced as its own distinct filesystem type.
> Otherwise, Fedora (and likely any other system enforcing SELinux)
> stopped working.
Woof. Not a hill I'm willing to receive even minor injuries on. Carry on.
^ permalink raw reply
* Re: [PATCH v4 15/17] module: Introduce hash-based integrity checking
From: Nicolas Schier @ 2026-02-24 16:14 UTC (permalink / raw)
To: Thomas Weißschuh
Cc: Nathan Chancellor, Arnd Bergmann, Luis Chamberlain, Petr Pavlu,
Sami Tolvanen, Daniel Gomez, Paul Moore, James Morris,
Serge E. Hallyn, Jonathan Corbet, Madhavan Srinivasan,
Michael Ellerman, Nicholas Piggin, Naveen N Rao, Mimi Zohar,
Roberto Sassu, Dmitry Kasatkin, Eric Snowberg, Daniel Gomez,
Aaron Tomlin, Christophe Leroy (CS GROUP), Nicolas Bouchinet,
Xiu Jianfeng, Fabian Grünbichler, Arnout Engelen,
Mattia Rizzolo, kpcyrd, Christian Heusel, Câju Mihai-Drosi,
Sebastian Andrzej Siewior, linux-kbuild, linux-kernel, linux-arch,
linux-modules, linux-security-module, linux-doc, linuxppc-dev,
linux-integrity
In-Reply-To: <06054e9a-2b7a-4063-98b8-7d6c539e543f@t-8ch.de>
On Mon, Feb 23, 2026 at 10:43:30PM +0100, Thomas Weißschuh wrote:
> On 2026-02-23 19:41:52+0100, Nicolas Schier wrote:
> > On Mon, Feb 23, 2026 at 08:53:29AM +0100, Thomas Weißschuh wrote:
> > > On 2026-02-21 22:38:29+0100, Nicolas Schier wrote:
> > > > On Tue, Jan 13, 2026 at 01:28:59PM +0100, Thomas Weißschuh wrote:
[...]
> > > > [...]
> > > > > diff --git a/scripts/modules-merkle-tree.c b/scripts/modules-merkle-tree.c
> > > > > new file mode 100644
> > > > > index 000000000000..a6ec0e21213b
> > > > > --- /dev/null
> > > > > +++ b/scripts/modules-merkle-tree.c
> > > > > @@ -0,0 +1,467 @@
> > > > > +// SPDX-License-Identifier: GPL-2.0-or-later
> > > > > +/*
> > > > > + * Compute hashes for modules files and build a merkle tree.
> > > > > + *
> > > > > + * Copyright (C) 2025 Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
> > > > > + * Copyright (C) 2025 Thomas Weißschuh <linux@weissschuh.net>
> > > > > + *
> > > > > + */
> > > > > +#define _GNU_SOURCE 1
> > > > > +#include <arpa/inet.h>
> > > > > +#include <err.h>
> > > > > +#include <unistd.h>
> > > > > +#include <fcntl.h>
> > > > > +#include <stdarg.h>
> > > > > +#include <stdio.h>
> > > > > +#include <string.h>
> > > > > +#include <stdbool.h>
> > > > > +#include <stdlib.h>
> > > > > +
> > > > > +#include <sys/stat.h>
> > > > > +#include <sys/mman.h>
> > > > > +
> > > > > +#include <openssl/evp.h>
> > > > > +#include <openssl/err.h>
> > > > > +
> > > > > +#include "ssl-common.h"
> > > > > +
> > > > > +static int hash_size;
> > > > > +static EVP_MD_CTX *ctx;
> > > > > +
> > > > > +struct module_signature {
> > > > > + uint8_t algo; /* Public-key crypto algorithm [0] */
> > > > > + uint8_t hash; /* Digest algorithm [0] */
> > > > > + uint8_t id_type; /* Key identifier type [PKEY_ID_PKCS7] */
> > > > > + uint8_t signer_len; /* Length of signer's name [0] */
> > > > > + uint8_t key_id_len; /* Length of key identifier [0] */
> > > > > + uint8_t __pad[3];
> > > > > + uint32_t sig_len; /* Length of signature data */
> > > > > +};
> > > > > +
> > > > > +#define PKEY_ID_MERKLE 3
> > > > > +
> > > > > +static const char magic_number[] = "~Module signature appended~\n";
> > > >
> > > > This here will be the forth definition of struct module_signature,
> > > > increasing the risk of unwanted diversion. I second Petr's suggestion
> > > > to reuse a _common_ definition instead.
> > >
> > > Ack.
> > >
> > > > (Here, even include/linux/module_signature.h could be included itself.)
> > >
> > > I'd like to avoid including internal headers from other components.
> > > We could move it to an UAPI header. Various other subsystems use those
> > > for not-really-UAPI but still ABI definitions.
> >
> > Yeah, ack.
>
> What exactly is the 'ack' for?
> * Avoiding to include internal headers?
> * Moving the definition to UAPI headers?
ah, sorry. I think reduction of duplicated definitions is good; moving
these definitions to UAPI headers sounds like a valid compromise to me.
> (...)
>
> > > > Can you verify if I get the mechanics roughly correct?
> > > >
> > > > * Modules are merkle tree leaves. Modules are built and logically
> > > > paired by the order from modules.order; a single left-over module is
> > > > paired with itself.
> > > >
> > > > * Hashes of paired modules are hashed again (branch node hash);
> > > > hashes of pairs of branch nodes' hashes are hashed again;
> > > > repeat until we reach the single merkle tree root hash
> > > >
> > > > * The final merkle tree root hash (and the count of tree levels) is
> > > > included in vmlinux
> > >
> > > The merkle tree code was written by Sebastian so he will have the best
> > > knowledge about it. But this is also my understanding.
> >
> > I'd like to see some (rough) description in Documentation or in a commit
> > message at least, otherwise future me will have to ask that again.
>
> Ack in general. I'd prefer to document it in a source code comment,
> though. That feels like the best fit to me.
Great, thanks.
--
Nicolas
^ permalink raw reply
* Re: [PATCH] lsm: move inode IS_PRIVATE checks to individual LSMs
From: Stephen Smalley @ 2026-02-24 14:44 UTC (permalink / raw)
To: Paul Moore
Cc: Casey Schaufler, danieldurning.work, linux-security-module,
selinux, linux-integrity, jmorris, serge, john.johansen, zohar,
roberto.sassu, dmitry.kasatkin, mic, takedakn, penguin-kernel
In-Reply-To: <CAHC9VhSp+X8YNocS7sDz+UyhdJh2yY8CRoi6dwV1eOGdCu9f9w@mail.gmail.com>
On Mon, Feb 23, 2026 at 5:21 PM Paul Moore <paul@paul-moore.com> wrote:
> I'm not going to argue with that, and perhaps that is a good next
> step: send a quick RFC patch to the VFS folks, with the LSM list CC'd,
> that drops setting the S_PRIVATE flag to see if they complain too
> loudly. Based on other threads, Christian is aware that we are
> starting to look at better/proper handling of pidfds/pidfs so he may
> be open to dropping S_PRIVATE since it doesn't really have much impact
> outside of the LSM, but who knows; the VFS folks have been growing a
> bit more anti-LSM as of late.
Adding S_PRIVATE to pidfs inodes was originally motivated by this bug report:
https://lore.kernel.org/linux-fsdevel/20240222190334.GA412503@dev-arch.thelio-3990X/
when pidfs was first introduced as its own distinct filesystem type.
Otherwise, Fedora (and likely any other system enforcing SELinux)
stopped working.
So we can't unconditionally remove S_PRIVATE from pidfs inodes without breaking
existing userspace/policy. If we want to introduce controls over pidfs
inodes and do so in a
backward-compatible manner, we have to either move the S_PRIVATE
handling into the
individual LSMs or introduce a new hook in pidfs_init_inode() to
determine whether or not to
set S_PRIVATE. Such a hook might also handle labeling the pidfs inode
although we'd have to
see if we have enough information there to do so fully. Note that such
an approach will still likely
end up leaving pidfs inodes created before initial policy load with
the S_PRIVATE flag and hence
uncontrolled; not sure if that is a problem in practice.
>
> diff --git a/fs/pidfs.c b/fs/pidfs.c
> index 318253344b5c..4cec73b4cbcf 100644
> --- a/fs/pidfs.c
> +++ b/fs/pidfs.c
> @@ -921,7 +921,7 @@ static int pidfs_init_inode(struct inode *inode, void *data)
> const struct pid *pid = data;
>
> inode->i_private = data;
> - inode->i_flags |= S_PRIVATE | S_ANON_INODE;
> + inode->i_flags |= S_ANON_INODE;
> /* We allow to set xattrs. */
> inode->i_flags &= ~S_IMMUTABLE;
> inode->i_mode |= S_IRWXU;
>
> --
> paul-moore.com
^ permalink raw reply
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