[PATCH v2 stable/linux-6.6.y 1/3] fs: prepare for adding LSM blob to backing_file
From: Cai Xinchen <hidden>
Date: 2026-06-27 06:29:08
Also in:
bpf, linux-fsdevel, linux-unionfs, lkml, selinux, stable
Subsystem:
filesystems (vfs and infrastructure), the rest · Maintainers:
Alexander Viro, Christian Brauner, Linus Torvalds
From: Amir Goldstein <amir73il@gmail.com>
[ Upstream commit 880bd496ec72a6dcb00cb70c430ef752ba242ae7 ]
In preparation to adding LSM blob to backing_file struct, factor out
helpers init_backing_file() and backing_file_free().
Cc: stable@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-unionfs@vger.kernel.org
Cc: linux-erofs@lists.ozlabs.org
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
[PM: use the term "LSM blob", fix comment style to match file]
Signed-off-by: Paul Moore <paul@paul-moore.com>
[1. The commit def3ae83da02
("fs: store real path instead of fake path in backing file f_path")
is not merged, The 6.6 LTS version accordingly operates on
&ff->real_path instead of &ff->user_path.
2. Mainline's file_free() does both the backing_file cleanup and the
kmem_cache_free() synchronously. Linux 6.6.y defers the actual kfree()
to file_free_rcu() via call_rcu(), so only path_put() is done
synchronously in file_free().]
Signed-off-by: Cai Xinchen <redacted>
---
fs/file_table.c | 20 +++++++++++++++++++-
1 file changed, 19 insertions(+), 1 deletion(-)
diff --git a/fs/file_table.c b/fs/file_table.c
index 234284ef72a9..b4c208a77153 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c@@ -72,11 +72,16 @@ static void file_free_rcu(struct rcu_head *head) kmem_cache_free(filp_cachep, f); } +static inline void backing_file_free(struct backing_file *ff) +{ + path_put(&ff->real_path); +} + static inline void file_free(struct file *f) { security_file_free(f); if (unlikely(f->f_mode & FMODE_BACKING)) - path_put(backing_file_real_path(f)); + backing_file_free(backing_file(f)); if (likely(!(f->f_mode & FMODE_NOACCOUNT))) percpu_counter_dec(&nr_files); call_rcu(&f->f_rcuhead, file_free_rcu);
@@ -252,6 +257,12 @@ struct file *alloc_empty_file_noaccount(int flags, const struct cred *cred) return f; } +static int init_backing_file(struct backing_file *ff) +{ + memset(&ff->real_path, 0, sizeof(ff->real_path)); + return 0; +} + /* * Variant of alloc_empty_file() that allocates a backing_file container * and doesn't check and modify nr_files.
@@ -274,7 +285,14 @@ struct file *alloc_empty_backing_file(int flags, const struct cred *cred) return ERR_PTR(error); } + /* The f_mode flags must be set before fput(). */ ff->file.f_mode |= FMODE_BACKING | FMODE_NOACCOUNT; + error = init_backing_file(ff); + if (unlikely(error)) { + fput(&ff->file); + return ERR_PTR(error); + } + return &ff->file; }
--
2.18.0.huawei.25