From e257039f0fc7da36ac3a522ef9a5cb4ae7852e67 Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Mon, 28 Feb 2022 23:04:20 -0500
Subject: [PATCH] mount_setattr(): clean the control flow and calling
conventions
separate the "cleanup" and "apply" codepaths (they have almost no overlap),
fold the "cleanup" into "prepare" (which eliminates the need of ->revert)
and make loops more idiomatic.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/namespace.c | 82 ++++++++++++++++++++++++--------------------------
1 file changed, 40 insertions(+), 42 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index 0e342e2ade83c..7017c85ea3e6c 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -82,7 +82,6 @@ struct mount_kattr {
unsigned int lookup_flags;
bool recurse;
struct user_namespace *mnt_userns;
- struct mount *revert;
};
/* /sys/fs */
@@ -4014,32 +4013,39 @@ static inline bool mnt_allow_writers(const struct mount_kattr *kattr,
static int mount_setattr_prepare(struct mount_kattr *kattr, struct mount *mnt)
{
- struct mount *m = mnt;
-
- do {
- int err = -EPERM;
- unsigned int flags;
-
- kattr->revert = m;
+ struct mount *m;
+ int err;
- flags = recalc_flags(kattr, m);
- if (!can_change_locked_flags(m, flags))
- return err;
+ for (m = mnt; m; m = next_mnt(m, mnt)) {
+ if (!can_change_locked_flags(m, recalc_flags(kattr, m))) {
+ err = -EPERM;
+ break;
+ }
err = can_idmap_mount(kattr, m);
if (err)
- return err;
+ break;
- if (mnt_allow_writers(kattr, m))
- continue;
+ if (!mnt_allow_writers(kattr, m)) {
+ err = mnt_hold_writers(m);
+ if (err)
+ break;
+ }
- err = mnt_hold_writers(m);
- if (err)
- return err;
- } while (kattr->recurse && (m = next_mnt(m, mnt)));
+ if (!kattr->recurse)
+ return 0;
+ }
- kattr->revert = NULL;
- return 0;
+ if (err) {
+ struct mount *p;
+
+ for (p = mnt; p != m; p = next_mnt(p, mnt)) {
+ /* If we had to hold writers unblock them. */
+ if (p->mnt.mnt_flags & MNT_WRITE_HOLD)
+ mnt_unhold_writers(p);
+ }
+ }
+ return err;
}
static void do_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt)
@@ -4067,36 +4073,27 @@ static void do_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt)
put_user_ns(old_mnt_userns);
}
-static void mount_setattr_finish(struct mount_kattr *kattr, struct mount *mnt)
+static void mount_setattr_commit(struct mount_kattr *kattr, struct mount *mnt)
{
- struct mount *m = mnt;
+ struct mount *m;
- do {
- if (!kattr->revert) {
- unsigned int flags;
+ for (m = mnt; m; m = next_mnt(m, mnt)) {
+ unsigned int flags;
- do_idmap_mount(kattr, m);
- flags = recalc_flags(kattr, m);
- WRITE_ONCE(m->mnt.mnt_flags, flags);
- }
+ do_idmap_mount(kattr, m);
+ flags = recalc_flags(kattr, m);
+ WRITE_ONCE(m->mnt.mnt_flags, flags);
/* If we had to hold writers unblock them. */
if (m->mnt.mnt_flags & MNT_WRITE_HOLD)
mnt_unhold_writers(m);
- if (!kattr->revert && kattr->propagation)
+ if (kattr->propagation)
change_mnt_propagation(m, kattr->propagation);
-
- /*
- * On failure, only cleanup until we found the first mount
- * we failed to handle.
- */
- if (kattr->revert == m)
- return;
- } while (kattr->recurse && (m = next_mnt(m, mnt)));
-
- if (!kattr->revert)
- touch_mnt_namespace(mnt->mnt_ns);
+ if (!kattr->recurse)
+ break;
+ }
+ touch_mnt_namespace(mnt->mnt_ns);
}
static int do_mount_setattr(struct path *path, struct mount_kattr *kattr)
@@ -4144,7 +4141,8 @@ static int do_mount_setattr(struct path *path, struct mount_kattr *kattr)
* changes and if we failed we clean up.
*/
err = mount_setattr_prepare(kattr, mnt);
- mount_setattr_finish(kattr, mnt);
+ if (!err)
+ mount_setattr_commit(kattr, mnt);
out:
unlock_mount_hash();
--
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