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Subject[PATCH v6 07/10] proc: flush task dcache entries from all procfs instances
Date
This allows to flush dcache entries of a task on multiple procfs mounts
per pid namespace.

Cc: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Djalal Harouni <tixxdz@gmail.com>
Signed-off-by: Alexey Gladkov <gladkov.alexey@gmail.com>
---
fs/proc/base.c | 23 ++++++++++++++-----
fs/proc/root.c | 14 ++++++++++++
include/linux/pid_namespace.h | 42 +++++++++++++++++++++++++++++++++++
include/linux/proc_fs.h | 2 ++
4 files changed, 76 insertions(+), 5 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 4ccb280a3e79..f4f1bcb28603 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -3133,7 +3133,7 @@ static const struct inode_operations proc_tgid_base_inode_operations = {
.permission = proc_pid_permission,
};

-static void proc_flush_task_mnt(struct vfsmount *mnt, pid_t pid, pid_t tgid)
+static void proc_flush_task_mnt_root(struct dentry *mnt_root, pid_t pid, pid_t tgid)
{
struct dentry *dentry, *leader, *dir;
char buf[10 + 1];
@@ -3142,7 +3142,7 @@ static void proc_flush_task_mnt(struct vfsmount *mnt, pid_t pid, pid_t tgid)
name.name = buf;
name.len = snprintf(buf, sizeof(buf), "%u", pid);
/* no ->d_hash() rejects on procfs */
- dentry = d_hash_and_lookup(mnt->mnt_root, &name);
+ dentry = d_hash_and_lookup(mnt_root, &name);
if (dentry) {
d_invalidate(dentry);
dput(dentry);
@@ -3153,7 +3153,7 @@ static void proc_flush_task_mnt(struct vfsmount *mnt, pid_t pid, pid_t tgid)

name.name = buf;
name.len = snprintf(buf, sizeof(buf), "%u", tgid);
- leader = d_hash_and_lookup(mnt->mnt_root, &name);
+ leader = d_hash_and_lookup(mnt_root, &name);
if (!leader)
goto out;

@@ -3208,14 +3208,27 @@ void proc_flush_task(struct task_struct *task)
int i;
struct pid *pid, *tgid;
struct upid *upid;
+ struct pid_namespace *pid_ns;
+ struct dentry *mnt_root;
+ struct proc_fs_info *fs_info;

pid = task_pid(task);
tgid = task_tgid(task);

for (i = 0; i <= pid->level; i++) {
upid = &pid->numbers[i];
- proc_flush_task_mnt(upid->ns->proc_mnt, upid->nr,
- tgid->numbers[i].nr);
+
+ pid_ns = upid->ns;
+
+ pidns_proc_lock_shared(pid_ns);
+ list_for_each_entry(fs_info, &pid_ns->proc_mounts, pidns_entry) {
+ mnt_root = fs_info->m_super->s_root;
+ proc_flush_task_mnt_root(mnt_root, upid->nr, tgid->numbers[i].nr);
+ }
+ pidns_proc_unlock_shared(pid_ns);
+
+ mnt_root = pid_ns->proc_mnt->mnt_root;
+ proc_flush_task_mnt_root(mnt_root, upid->nr, tgid->numbers[i].nr);
}
}

diff --git a/fs/proc/root.c b/fs/proc/root.c
index 5d5cba4c899b..3bb8df360cf7 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -112,6 +112,12 @@ static int proc_fill_super(struct super_block *s, struct fs_context *fc)

proc_apply_options(ctx->fs_info, fc, pid_ns, current_user_ns());

+ ctx->fs_info->m_super = s;
+
+ pidns_proc_lock(pid_ns);
+ list_add_tail(&ctx->fs_info->pidns_entry, &pid_ns->proc_mounts);
+ pidns_proc_unlock(pid_ns);
+
/* User space would break if executables or devices appear on proc */
s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV;
s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC;
@@ -215,6 +221,11 @@ static void proc_kill_sb(struct super_block *sb)
dput(fs_info->proc_self);
if (fs_info->proc_thread_self)
dput(fs_info->proc_thread_self);
+
+ pidns_proc_lock(fs_info->pid_ns);
+ list_del(&fs_info->pidns_entry);
+ pidns_proc_unlock(fs_info->pid_ns);
+
kill_anon_super(sb);
put_pid_ns(fs_info->pid_ns);
kfree(fs_info);
@@ -336,6 +347,9 @@ int pid_ns_prepare_proc(struct pid_namespace *ns)
ctx->fs_info->pid_ns = ns;
}

+ init_rwsem(&ns->rw_proc_mounts);
+ INIT_LIST_HEAD(&ns->proc_mounts);
+
mnt = fc_mount(fc);
put_fs_context(fc);
if (IS_ERR(mnt))
diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index 66f47f1afe0d..297b39604312 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -26,6 +26,8 @@ struct pid_namespace {
struct pid_namespace *parent;
#ifdef CONFIG_PROC_FS
struct vfsmount *proc_mnt; /* Internal proc mounted during each new pidns */
+ struct rw_semaphore rw_proc_mounts;
+ struct list_head proc_mounts; /* list of separated procfs mounts */
#endif
#ifdef CONFIG_BSD_PROCESS_ACCT
struct fs_pin *bacct;
@@ -90,4 +92,44 @@ extern struct pid_namespace *task_active_pid_ns(struct task_struct *tsk);
void pidhash_init(void);
void pid_idr_init(void);

+#ifdef CONFIG_PROC_FS
+static inline void pidns_proc_lock(struct pid_namespace *pid_ns)
+{
+ down_write(&pid_ns->rw_proc_mounts);
+}
+
+static inline void pidns_proc_unlock(struct pid_namespace *pid_ns)
+{
+ up_write(&pid_ns->rw_proc_mounts);
+}
+
+static inline void pidns_proc_lock_shared(struct pid_namespace *pid_ns)
+{
+ down_read(&pid_ns->rw_proc_mounts);
+}
+
+static inline void pidns_proc_unlock_shared(struct pid_namespace *pid_ns)
+{
+ up_read(&pid_ns->rw_proc_mounts);
+}
+#else /* !CONFIG_PROC_FS */
+
+static inline void pidns_proc_lock(struct pid_namespace *pid_ns)
+{
+}
+
+static inline void pidns_proc_unlock(struct pid_namespace *pid_ns)
+{
+}
+
+static inline void pidns_proc_lock_shared(struct pid_namespace *pid_ns)
+{
+}
+
+static inline void pidns_proc_unlock_shared(struct pid_namespace *pid_ns)
+{
+}
+
+#endif /* CONFIG_PROC_FS */
+
#endif /* _LINUX_PID_NS_H */
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index fd92bf38aa62..e349fcafd729 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -20,6 +20,8 @@ enum {
};

struct proc_fs_info {
+ struct list_head pidns_entry; /* Node in procfs_mounts of a pidns */
+ struct super_block *m_super;
struct pid_namespace *pid_ns;
struct dentry *proc_self; /* For /proc/self */
struct dentry *proc_thread_self; /* For /proc/thread-self */
--
2.24.1
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