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From: Daniel Colascione <dancol@google.com>
To: timmurray@google.com, selinux@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	kvm@vger.kernel.org, viro@zeniv.linux.org.uk,
	paul@paul-moore.com, nnk@google.com, sds@tycho.nsa.gov,
	lokeshgidra@google.com, jmorris@namei.org
Cc: Daniel Colascione <dancol@google.com>
Subject: [PATCH v3 3/3] Wire UFFD up to SELinux
Date: Thu, 26 Mar 2020 11:14:56 -0700
Message-ID: <20200326181456.132742-4-dancol@google.com> (raw)
In-Reply-To: <20200326181456.132742-1-dancol@google.com>

This change gives userfaultfd file descriptors a real security
context, allowing policy to act on them.

Signed-off-by: Daniel Colascione <dancol@google.com>
---
 fs/userfaultfd.c | 34 +++++++++++++++++++++++++++++-----
 1 file changed, 29 insertions(+), 5 deletions(-)

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 07b0f6e03849..78ff5d898733 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -76,6 +76,8 @@ struct userfaultfd_ctx {
 	bool mmap_changing;
 	/* mm with one ore more vmas attached to this userfaultfd_ctx */
 	struct mm_struct *mm;
+	/* The inode that owns this context --- not a strong reference.  */
+	const struct inode *owner;
 };
 
 struct userfaultfd_fork_ctx {
@@ -1014,14 +1016,18 @@ static __poll_t userfaultfd_poll(struct file *file, poll_table *wait)
 	}
 }
 
+static const struct file_operations userfaultfd_fops;
+
 static int resolve_userfault_fork(struct userfaultfd_ctx *ctx,
 				  struct userfaultfd_ctx *new,
 				  struct uffd_msg *msg)
 {
 	int fd;
 
-	fd = anon_inode_getfd("[userfaultfd]", &userfaultfd_fops, new,
-			      O_RDWR | (new->flags & UFFD_SHARED_FCNTL_FLAGS));
+	fd = anon_inode_getfd_secure(
+		"[userfaultfd]", &userfaultfd_fops, new,
+		O_RDWR | (new->flags & UFFD_SHARED_FCNTL_FLAGS),
+		ctx->owner);
 	if (fd < 0)
 		return fd;
 
@@ -1918,7 +1924,7 @@ static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f)
 }
 #endif
 
-const struct file_operations userfaultfd_fops = {
+static const struct file_operations userfaultfd_fops = {
 #ifdef CONFIG_PROC_FS
 	.show_fdinfo	= userfaultfd_show_fdinfo,
 #endif
@@ -1943,6 +1949,7 @@ static void init_once_userfaultfd_ctx(void *mem)
 
 SYSCALL_DEFINE1(userfaultfd, int, flags)
 {
+	struct file *file;
 	struct userfaultfd_ctx *ctx;
 	int fd;
 
@@ -1972,8 +1979,25 @@ SYSCALL_DEFINE1(userfaultfd, int, flags)
 	/* prevent the mm struct to be freed */
 	mmgrab(ctx->mm);
 
-	fd = anon_inode_getfd("[userfaultfd]", &userfaultfd_fops, ctx,
-			      O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS));
+	file = anon_inode_getfile_secure(
+		"[userfaultfd]", &userfaultfd_fops, ctx,
+		O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS),
+		NULL);
+	if (IS_ERR(file)) {
+		fd = PTR_ERR(file);
+		goto out;
+	}
+
+	fd = get_unused_fd_flags(O_RDONLY | O_CLOEXEC);
+	if (fd < 0) {
+		fput(file);
+		goto out;
+	}
+
+	ctx->owner = file_inode(file);
+	fd_install(fd, file);
+
+out:
 	if (fd < 0) {
 		mmdrop(ctx->mm);
 		kmem_cache_free(userfaultfd_ctx_cachep, ctx);
-- 
2.25.1.696.g5e7596f4ac-goog


  parent reply index

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20200211225547.235083-1-dancol@google.com>
2020-02-14  3:26 ` [PATCH 0/3] SELinux support for anonymous inodes and UFFD Daniel Colascione
2020-02-14  3:26   ` [PATCH 1/3] Add a new LSM-supporting anonymous inode interface Daniel Colascione
2020-02-14  3:26   ` [PATCH 2/3] Teach SELinux about anonymous inodes Daniel Colascione
2020-02-14 16:39     ` Stephen Smalley
2020-02-14 17:21       ` Daniel Colascione
2020-02-14 18:02         ` Stephen Smalley
2020-02-14 18:08           ` Stephen Smalley
2020-02-14 20:24             ` Stephen Smalley
2020-02-14  3:26   ` [PATCH 3/3] Wire UFFD up to SELinux Daniel Colascione
2020-03-25 23:02   ` [PATCH v2 0/3] SELinux support for anonymous inodes and UFFD Daniel Colascione
2020-03-25 23:02   ` [PATCH v2 1/3] Add a new LSM-supporting anonymous inode interface Daniel Colascione
2020-03-26 13:53     ` Stephen Smalley
2020-03-25 23:02   ` [PATCH v2 2/3] Teach SELinux about anonymous inodes Daniel Colascione
2020-03-26 13:58     ` Stephen Smalley
2020-03-26 17:59       ` Daniel Colascione
2020-03-26 17:37     ` Stephen Smalley
2020-03-25 23:02   ` [PATCH v2 3/3] Wire UFFD up to SELinux Daniel Colascione
2020-03-25 23:49     ` Casey Schaufler
2020-03-26 18:14   ` [PATCH v3 0/3] SELinux support for anonymous inodes and UFFD Daniel Colascione
2020-03-26 18:14     ` [PATCH v3 1/3] Add a new LSM-supporting anonymous inode interface Daniel Colascione
2020-03-26 19:00       ` Stephen Smalley
2020-03-26 18:14     ` [PATCH v3 2/3] Teach SELinux about anonymous inodes Daniel Colascione
2020-03-26 19:02       ` Stephen Smalley
2020-03-26 18:14     ` Daniel Colascione [this message]
2020-03-26 20:06     ` [PATCH v4 0/3] SELinux support for anonymous inodes and UFFD Daniel Colascione
2020-03-26 20:06       ` [PATCH v4 1/3] Add a new LSM-supporting anonymous inode interface Daniel Colascione
2020-03-27 13:40         ` Stephen Smalley
2020-03-26 20:06       ` [PATCH v4 2/3] Teach SELinux about anonymous inodes Daniel Colascione
2020-03-27 13:41         ` Stephen Smalley
2020-03-26 20:06       ` [PATCH v4 3/3] Wire UFFD up to SELinux Daniel Colascione
2020-04-01 21:39       ` [PATCH v5 0/3] SELinux support for anonymous inodes and UFFD Daniel Colascione
2020-04-01 21:39         ` [PATCH v5 1/3] Add a new LSM-supporting anonymous inode interface Daniel Colascione
2020-05-07 16:02           ` James Morris
2020-04-01 21:39         ` [PATCH v5 2/3] Teach SELinux about anonymous inodes Daniel Colascione
2020-04-01 21:39         ` [PATCH v5 3/3] Wire UFFD up to SELinux Daniel Colascione
2020-04-13 13:29         ` [PATCH v5 0/3] SELinux support for anonymous inodes and UFFD Daniel Colascione
2020-04-22 16:55           ` James Morris
2020-04-22 17:12             ` Casey Schaufler
2020-04-23 22:24               ` Casey Schaufler
2020-04-27 16:18                 ` Casey Schaufler
2020-04-27 16:48                   ` Stephen Smalley
2020-04-27 17:12                     ` Casey Schaufler
2020-04-29 17:02                     ` Stephen Smalley
2020-04-27 17:15             ` Casey Schaufler
2020-04-27 19:40               ` Stephen Smalley

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