summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
Diffstat
-rw-r--r--fs/fs_context.c1
-rw-r--r--fs/fsopen.c106
-rw-r--r--fs/super.c64
-rw-r--r--include/linux/fs_context.h4
-rw-r--r--include/uapi/linux/mount.h3
5 files changed, 107 insertions, 71 deletions
diff --git a/fs/fs_context.c b/fs/fs_context.c
index 851214d1d013..30d82d2979af 100644
--- a/fs/fs_context.c
+++ b/fs/fs_context.c
@@ -692,6 +692,7 @@ void vfs_clean_context(struct fs_context *fc)
security_free_mnt_opts(&fc->security);
kfree(fc->source);
fc->source = NULL;
+ fc->exclusive = false;
fc->purpose = FS_CONTEXT_FOR_RECONFIGURE;
fc->phase = FS_CONTEXT_AWAITING_RECONF;
diff --git a/fs/fsopen.c b/fs/fsopen.c
index fc9d2d9fd234..ce03f6521c88 100644
--- a/fs/fsopen.c
+++ b/fs/fsopen.c
@@ -209,6 +209,72 @@ err:
return ret;
}
+static int vfs_cmd_create(struct fs_context *fc, bool exclusive)
+{
+ struct super_block *sb;
+ int ret;
+
+ if (fc->phase != FS_CONTEXT_CREATE_PARAMS)
+ return -EBUSY;
+
+ if (!mount_capable(fc))
+ return -EPERM;
+
+ /* require the new mount api */
+ if (exclusive && fc->ops == &legacy_fs_context_ops)
+ return -EOPNOTSUPP;
+
+ fc->phase = FS_CONTEXT_CREATING;
+ fc->exclusive = exclusive;
+
+ ret = vfs_get_tree(fc);
+ if (ret) {
+ fc->phase = FS_CONTEXT_FAILED;
+ return ret;
+ }
+
+ sb = fc->root->d_sb;
+ ret = security_sb_kern_mount(sb);
+ if (unlikely(ret)) {
+ fc_drop_locked(fc);
+ fc->phase = FS_CONTEXT_FAILED;
+ return ret;
+ }
+
+ /* vfs_get_tree() callchains will have grabbed @s_umount */
+ up_write(&sb->s_umount);
+ fc->phase = FS_CONTEXT_AWAITING_MOUNT;
+ return 0;
+}
+
+static int vfs_cmd_reconfigure(struct fs_context *fc)
+{
+ struct super_block *sb;
+ int ret;
+
+ if (fc->phase != FS_CONTEXT_RECONF_PARAMS)
+ return -EBUSY;
+
+ fc->phase = FS_CONTEXT_RECONFIGURING;
+
+ sb = fc->root->d_sb;
+ if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) {
+ fc->phase = FS_CONTEXT_FAILED;
+ return -EPERM;
+ }
+
+ down_write(&sb->s_umount);
+ ret = reconfigure_super(fc);
+ up_write(&sb->s_umount);
+ if (ret) {
+ fc->phase = FS_CONTEXT_FAILED;
+ return ret;
+ }
+
+ vfs_clean_context(fc);
+ return 0;
+}
+
/*
* Check the state and apply the configuration. Note that this function is
* allowed to 'steal' the value by setting param->xxx to NULL before returning.
@@ -216,7 +282,6 @@ err:
static int vfs_fsconfig_locked(struct fs_context *fc, int cmd,
struct fs_parameter *param)
{
- struct super_block *sb;
int ret;
ret = finish_clean_context(fc);
@@ -224,39 +289,11 @@ static int vfs_fsconfig_locked(struct fs_context *fc, int cmd,
return ret;
switch (cmd) {
case FSCONFIG_CMD_CREATE:
- if (fc->phase != FS_CONTEXT_CREATE_PARAMS)
- return -EBUSY;
- if (!mount_capable(fc))
- return -EPERM;
- fc->phase = FS_CONTEXT_CREATING;
- ret = vfs_get_tree(fc);
- if (ret)
- break;
- sb = fc->root->d_sb;
- ret = security_sb_kern_mount(sb);
- if (unlikely(ret)) {
- fc_drop_locked(fc);
- break;
- }
- up_write(&sb->s_umount);
- fc->phase = FS_CONTEXT_AWAITING_MOUNT;
- return 0;
+ return vfs_cmd_create(fc, false);
+ case FSCONFIG_CMD_CREATE_EXCL:
+ return vfs_cmd_create(fc, true);
case FSCONFIG_CMD_RECONFIGURE:
- if (fc->phase != FS_CONTEXT_RECONF_PARAMS)
- return -EBUSY;
- fc->phase = FS_CONTEXT_RECONFIGURING;
- sb = fc->root->d_sb;
- if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) {
- ret = -EPERM;
- break;
- }
- down_write(&sb->s_umount);
- ret = reconfigure_super(fc);
- up_write(&sb->s_umount);
- if (ret)
- break;
- vfs_clean_context(fc);
- return 0;
+ return vfs_cmd_reconfigure(fc);
default:
if (fc->phase != FS_CONTEXT_CREATE_PARAMS &&
fc->phase != FS_CONTEXT_RECONF_PARAMS)
@@ -264,8 +301,6 @@ static int vfs_fsconfig_locked(struct fs_context *fc, int cmd,
return vfs_parse_fs_param(fc, param);
}
- fc->phase = FS_CONTEXT_FAILED;
- return ret;
}
/**
@@ -353,6 +388,7 @@ SYSCALL_DEFINE5(fsconfig,
return -EINVAL;
break;
case FSCONFIG_CMD_CREATE:
+ case FSCONFIG_CMD_CREATE_EXCL:
case FSCONFIG_CMD_RECONFIGURE:
if (_key || _value || aux)
return -EINVAL;
diff --git a/fs/super.c b/fs/super.c
index e781226e2880..e04a403dbffd 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -546,17 +546,31 @@ bool mount_capable(struct fs_context *fc)
* @test: Comparison callback
* @set: Setup callback
*
- * Find or create a superblock using the parameters stored in the filesystem
- * context and the two callback functions.
+ * Create a new superblock or find an existing one.
*
- * If an extant superblock is matched, then that will be returned with an
- * elevated reference count that the caller must transfer or discard.
+ * The @test callback is used to find a matching existing superblock.
+ * Whether or not the requested parameters in @fc are taken into account
+ * is specific to the @test callback that is used. They may even be
+ * completely ignored.
+ *
+ * If an extant superblock is matched, it will be returned unless:
+ *
+ * (1) the namespace the filesystem context @fc and the extant
+ * superblock's namespace differ
+ *
+ * (2) the filesystem context @fc has requested that reusing an extant
+ * superblock is not allowed
+ *
+ * In both cases EBUSY will be returned.
*
* If no match is made, a new superblock will be allocated and basic
- * initialisation will be performed (s_type, s_fs_info and s_id will be set and
- * the set() callback will be invoked), the superblock will be published and it
- * will be returned in a partially constructed state with SB_BORN and SB_ACTIVE
- * as yet unset.
+ * initialisation will be performed (s_type, s_fs_info and s_id will be
+ * set and the @set callback will be invoked), the superblock will be
+ * published and it will be returned in a partially constructed state
+ * with SB_BORN and SB_ACTIVE as yet unset.
+ *
+ * Return: On success, an extant or newly created superblock is
+ * returned. On failure an error pointer is returned.
*/
struct super_block *sget_fc(struct fs_context *fc,
int (*test)(struct super_block *, struct fs_context *),
@@ -603,9 +617,13 @@ retry:
return s;
share_extant_sb:
- if (user_ns != old->s_user_ns) {
+ if (user_ns != old->s_user_ns || fc->exclusive) {
spin_unlock(&sb_lock);
destroy_unused_super(s);
+ if (fc->exclusive)
+ warnfc(fc, "reusing existing filesystem not allowed");
+ else
+ warnfc(fc, "reusing existing filesystem in another namespace not allowed");
return ERR_PTR(-EBUSY);
}
if (!grab_super(old))
@@ -1136,7 +1154,7 @@ static int test_single_super(struct super_block *s, struct fs_context *fc)
return 1;
}
-static int vfs_get_super(struct fs_context *fc, bool reconf,
+static int vfs_get_super(struct fs_context *fc,
int (*test)(struct super_block *, struct fs_context *),
int (*fill_super)(struct super_block *sb,
struct fs_context *fc))
@@ -1154,19 +1172,9 @@ static int vfs_get_super(struct fs_context *fc, bool reconf,
goto error;
sb->s_flags |= SB_ACTIVE;
- fc->root = dget(sb->s_root);
- } else {
- fc->root = dget(sb->s_root);
- if (reconf) {
- err = reconfigure_super(fc);
- if (err < 0) {
- dput(fc->root);
- fc->root = NULL;
- goto error;
- }
- }
}
+ fc->root = dget(sb->s_root);
return 0;
error:
@@ -1178,7 +1186,7 @@ int get_tree_nodev(struct fs_context *fc,
int (*fill_super)(struct super_block *sb,
struct fs_context *fc))
{
- return vfs_get_super(fc, false, NULL, fill_super);
+ return vfs_get_super(fc, NULL, fill_super);
}
EXPORT_SYMBOL(get_tree_nodev);
@@ -1186,25 +1194,17 @@ int get_tree_single(struct fs_context *fc,
int (*fill_super)(struct super_block *sb,
struct fs_context *fc))
{
- return vfs_get_super(fc, false, test_single_super, fill_super);
+ return vfs_get_super(fc, test_single_super, fill_super);
}
EXPORT_SYMBOL(get_tree_single);
-int get_tree_single_reconf(struct fs_context *fc,
- int (*fill_super)(struct super_block *sb,
- struct fs_context *fc))
-{
- return vfs_get_super(fc, true, test_single_super, fill_super);
-}
-EXPORT_SYMBOL(get_tree_single_reconf);
-
int get_tree_keyed(struct fs_context *fc,
int (*fill_super)(struct super_block *sb,
struct fs_context *fc),
void *key)
{
fc->s_fs_info = key;
- return vfs_get_super(fc, false, test_keyed_super, fill_super);
+ return vfs_get_super(fc, test_keyed_super, fill_super);
}
EXPORT_SYMBOL(get_tree_keyed);
diff --git a/include/linux/fs_context.h b/include/linux/fs_context.h
index ff6341e09925..a33a3b1d9016 100644
--- a/include/linux/fs_context.h
+++ b/include/linux/fs_context.h
@@ -109,6 +109,7 @@ struct fs_context {
bool need_free:1; /* Need to call ops->free() */
bool global:1; /* Goes into &init_user_ns */
bool oldapi:1; /* Coming from mount(2) */
+ bool exclusive:1; /* create new superblock, reject existing one */
};
struct fs_context_operations {
@@ -150,9 +151,6 @@ extern int get_tree_nodev(struct fs_context *fc,
extern int get_tree_single(struct fs_context *fc,
int (*fill_super)(struct super_block *sb,
struct fs_context *fc));
-extern int get_tree_single_reconf(struct fs_context *fc,
- int (*fill_super)(struct super_block *sb,
- struct fs_context *fc));
extern int get_tree_keyed(struct fs_context *fc,
int (*fill_super)(struct super_block *sb,
struct fs_context *fc),
diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h
index 8eb0d7b758d2..bb242fdcfe6b 100644
--- a/include/uapi/linux/mount.h
+++ b/include/uapi/linux/mount.h
@@ -100,8 +100,9 @@ enum fsconfig_command {
FSCONFIG_SET_PATH = 3, /* Set parameter, supplying an object by path */
FSCONFIG_SET_PATH_EMPTY = 4, /* Set parameter, supplying an object by (empty) path */
FSCONFIG_SET_FD = 5, /* Set parameter, supplying an object by fd */
- FSCONFIG_CMD_CREATE = 6, /* Invoke superblock creation */
+ FSCONFIG_CMD_CREATE = 6, /* Create new or reuse existing superblock */
FSCONFIG_CMD_RECONFIGURE = 7, /* Invoke superblock reconfiguration */
+ FSCONFIG_CMD_CREATE_EXCL = 8, /* Create new superblock, fail if reusing existing superblock */
};
/*
generated by cgit v1.2.3 (git 2.39.0) at 2024-07-28 09:00:25 +0300