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From: Aleksa Sarai <cyphar@cyphar.com>
To: Al Viro <viro@zeniv.linux.org.uk>,
	Jeff Layton <jlayton@kernel.org>,
	"J. Bruce Fields" <bfields@fieldses.org>,
	Arnd Bergmann <arnd@arndb.de>,
	David Howells <dhowells@redhat.com>,
	Shuah Khan <shuah@kernel.org>,
	Shuah Khan <skhan@linuxfoundation.org>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Christian Brauner <christian@brauner.io>
Cc: Aleksa Sarai <cyphar@cyphar.com>,
	Eric Biederman <ebiederm@xmission.com>,
	Andy Lutomirski <luto@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Kees Cook <keescook@chromium.org>, Jann Horn <jannh@google.com>,
	Tycho Andersen <tycho@tycho.ws>,
	David Drysdale <drysdale@google.com>,
	Chanho Min <chanho.min@lge.com>, Oleg Nesterov <oleg@redhat.com>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	Aleksa Sarai <asarai@suse.de>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	containers@lists.linux-foundation.org,
	linux-alpha@vger.kernel.org, linux-api@vger.kernel.org,
	linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-fsdevel@vger.kernel.org, linux-ia64@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
	linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org,
	linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	linux-s390@vger.kernel.org, linux-sh@vger.kernel.org,
	linux-xtensa@linux-xtensa.org, sparclinux@vger.kernel.org
Subject: [PATCH v12 06/12] procfs: switch magic-link modes to be more sane
Date: Thu,  5 Sep 2019 06:19:27 +1000
Message-ID: <20190904201933.10736-7-cyphar@cyphar.com> (raw)
In-Reply-To: <20190904201933.10736-1-cyphar@cyphar.com>

Now that magic-link modes are obeyed for file re-opening purposes, some
of the pre-existing magic-link modes need to be adjusted to be more
semantically correct.

The most blatant example of this is /proc/self/exe, which had a mode of
a+rwx even though tautologically the file could never be opened for
writing (because it is the current->mm of a live process).

With the new O_PATH restrictions, changing the default mode of these
magic-links allows us to avoid delayed-access attacks such as we saw in
CVE-2019-5736.

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
---
 fs/proc/base.c       | 20 ++++++++++----------
 fs/proc/namespaces.c |  2 +-
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index ebea9501afb8..297242174402 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -133,9 +133,9 @@ struct pid_entry {
 
 #define DIR(NAME, MODE, iops, fops)	\
 	NOD(NAME, (S_IFDIR|(MODE)), &iops, &fops, {} )
-#define LNK(NAME, get_link)					\
-	NOD(NAME, (S_IFLNK|S_IRWXUGO),				\
-		&proc_pid_link_inode_operations, NULL,		\
+#define LNK(NAME, MODE, get_link)			\
+	NOD(NAME, (S_IFLNK|(MODE)),			\
+		&proc_pid_link_inode_operations, NULL,	\
 		{ .proc_get_link = get_link } )
 #define REG(NAME, MODE, fops)				\
 	NOD(NAME, (S_IFREG|(MODE)), NULL, &fops, {})
@@ -3028,9 +3028,9 @@ static const struct pid_entry tgid_base_stuff[] = {
 	REG("numa_maps",  S_IRUGO, proc_pid_numa_maps_operations),
 #endif
 	REG("mem",        S_IRUSR|S_IWUSR, proc_mem_operations),
-	LNK("cwd",        proc_cwd_link),
-	LNK("root",       proc_root_link),
-	LNK("exe",        proc_exe_link),
+	LNK("cwd",        S_IRWXUGO, proc_cwd_link),
+	LNK("root",       S_IRWXUGO, proc_root_link),
+	LNK("exe",        S_IRUGO|S_IXUGO, proc_exe_link),
 	REG("mounts",     S_IRUGO, proc_mounts_operations),
 	REG("mountinfo",  S_IRUGO, proc_mountinfo_operations),
 	REG("mountstats", S_IRUSR, proc_mountstats_operations),
@@ -3429,11 +3429,11 @@ static const struct pid_entry tid_base_stuff[] = {
 	REG("numa_maps", S_IRUGO, proc_pid_numa_maps_operations),
 #endif
 	REG("mem",       S_IRUSR|S_IWUSR, proc_mem_operations),
-	LNK("cwd",       proc_cwd_link),
-	LNK("root",      proc_root_link),
-	LNK("exe",       proc_exe_link),
+	LNK("cwd",       S_IRWXUGO, proc_cwd_link),
+	LNK("root",      S_IRWXUGO, proc_root_link),
+	LNK("exe",       S_IRUGO|S_IXUGO, proc_exe_link),
 	REG("mounts",    S_IRUGO, proc_mounts_operations),
-	REG("mountinfo",  S_IRUGO, proc_mountinfo_operations),
+	REG("mountinfo", S_IRUGO, proc_mountinfo_operations),
 #ifdef CONFIG_PROC_PAGE_MONITOR
 	REG("clear_refs", S_IWUSR, proc_clear_refs_operations),
 	REG("smaps",     S_IRUGO, proc_pid_smaps_operations),
diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c
index dd2b35f78b09..cd1e130913f7 100644
--- a/fs/proc/namespaces.c
+++ b/fs/proc/namespaces.c
@@ -94,7 +94,7 @@ static struct dentry *proc_ns_instantiate(struct dentry *dentry,
 	struct inode *inode;
 	struct proc_inode *ei;
 
-	inode = proc_pid_make_inode(dentry->d_sb, task, S_IFLNK | S_IRWXUGO);
+	inode = proc_pid_make_inode(dentry->d_sb, task, S_IFLNK | S_IRUGO);
 	if (!inode)
 		return ERR_PTR(-ENOENT);
 
-- 
2.23.0


  parent reply index

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-04 20:19 [PATCH v12 00/12] namei: openat2(2) path resolution restrictions Aleksa Sarai
2019-09-04 20:19 ` [PATCH v12 01/12] lib: introduce copy_struct_{to,from}_user helpers Aleksa Sarai
2019-09-04 20:48   ` Linus Torvalds
2019-09-04 21:00   ` Randy Dunlap
2019-09-05  7:32   ` Peter Zijlstra
2019-09-05  9:26     ` Aleksa Sarai
2019-09-05  9:43       ` Peter Zijlstra
2019-09-05 10:57         ` Peter Zijlstra
2019-09-11 10:37           ` Aleksa Sarai
2019-09-05 13:35         ` Aleksa Sarai
2019-09-05 17:01         ` Aleksa Sarai
2019-09-05  8:43   ` Rasmus Villemoes
2019-09-05  9:50     ` Aleksa Sarai
2019-09-05 10:45       ` Christian Brauner
2019-09-05  9:09   ` Andreas Schwab
2019-09-05 10:13     ` [PATCH v12 01/12] lib: introduce copy_struct_{to, from}_user helpers Gabriel Paubert
2019-09-05 11:05   ` [PATCH v12 01/12] lib: introduce copy_struct_{to,from}_user helpers Christian Brauner
2019-09-05 11:17     ` Rasmus Villemoes
2019-09-05 11:29       ` Christian Brauner
2019-09-05 13:40     ` Aleksa Sarai
2019-09-05 11:09   ` Christian Brauner
2019-09-05 11:27     ` Aleksa Sarai
2019-09-05 11:40       ` Christian Brauner
2019-09-05 18:07   ` Al Viro
2019-09-05 18:23     ` Christian Brauner
2019-09-05 18:28       ` Al Viro
2019-09-05 18:35         ` Christian Brauner
2019-09-05 19:56         ` Aleksa Sarai
2019-09-05 22:31           ` Al Viro
2019-09-06  7:00           ` Christian Brauner
2019-09-05 23:00     ` Aleksa Sarai
2019-09-05 23:49       ` Al Viro
2019-09-06  0:09         ` Aleksa Sarai
2019-09-06  0:14         ` Al Viro
2019-09-04 20:19 ` [PATCH v12 02/12] clone3: switch to copy_struct_from_user() Aleksa Sarai
2019-09-04 20:19 ` [PATCH v12 03/12] sched_setattr: switch to copy_struct_{to,from}_user() Aleksa Sarai
2019-09-04 20:19 ` [PATCH v12 04/12] perf_event_open: switch to copy_struct_from_user() Aleksa Sarai
2019-09-04 20:19 ` [PATCH v12 05/12] namei: obey trailing magic-link DAC permissions Aleksa Sarai
2019-09-17 21:30   ` Jann Horn
2019-09-18 13:51     ` Aleksa Sarai
2019-09-18 15:46       ` Aleksa Sarai
2019-09-04 20:19 ` Aleksa Sarai [this message]
2019-09-04 20:19 ` [PATCH v12 07/12] open: O_EMPTYPATH: procfs-less file descriptor re-opening Aleksa Sarai
2019-09-04 20:19 ` [PATCH v12 08/12] namei: O_BENEATH-style path resolution flags Aleksa Sarai
2019-09-04 20:19 ` [PATCH v12 09/12] namei: LOOKUP_IN_ROOT: chroot-like path resolution Aleksa Sarai
2019-09-04 20:19 ` [PATCH v12 10/12] namei: aggressively check for nd->root escape on ".." resolution Aleksa Sarai
2019-09-04 21:09   ` Linus Torvalds
2019-09-04 21:35     ` Linus Torvalds
2019-09-04 21:36       ` Linus Torvalds
2019-09-04 21:48     ` Aleksa Sarai
2019-09-04 22:16       ` Linus Torvalds
2019-09-04 22:31       ` David Howells
2019-09-04 22:38         ` Linus Torvalds
2019-09-04 23:29           ` Al Viro
2019-09-04 23:44             ` Linus Torvalds
2019-09-04 20:19 ` [PATCH v12 11/12] open: openat2(2) syscall Aleksa Sarai
2019-09-04 21:00   ` Randy Dunlap
2019-09-07 12:40   ` Jeff Layton
2019-09-07 16:58     ` Linus Torvalds
2019-09-07 17:42       ` Andy Lutomirski
2019-09-07 17:45         ` Linus Torvalds
2019-09-07 18:15           ` Andy Lutomirski
2019-09-10  6:35           ` Ingo Molnar
2019-09-08 16:24     ` Aleksa Sarai
2019-09-04 20:19 ` [PATCH v12 12/12] selftests: add openat2(2) selftests Aleksa Sarai

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