From: Calvin Owens <calvinowens@fb.com>
To: Cyrill Gorcunov <gorcunov@gmail.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Andrew Morton <akpm@linux-foundation.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>,
Oleg Nesterov <oleg@redhat.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Al Viro <viro@zeniv.linux.org.uk>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Peter Feiner <pfeiner@google.com>,
Grant Likely <grant.likely@secretlab.ca>,
Siddhesh Poyarekar <siddhesh.poyarekar@gmail.com>,
<linux-kernel@vger.kernel.org>, <kernel-team@fb.com>,
Pavel Emelyanov <xemul@openvz.org>
Subject: [PATCH] procfs: Return -ESRCH on /proc/N/fd/* when PID N doesn't exist
Date: Sat, 14 Feb 2015 12:44:52 -0800 [thread overview]
Message-ID: <20150214204452.GA1777871@mail.thefacebook.com> (raw)
In-Reply-To: <20150212022910.GA3247638@mail.thefacebook.com>
Currently, readlink() and follow_link() for the symbolic links in
/proc/<pid>/fd/* will return -EACCES in the case where looking up the
task finds that it does not exist.
This patch inlines the logic from proc_fd_access_allowed() into these
two functions such that they will return -ESRCH if the lookup in /proc
races with the task exiting. Since those were the only two callers of
that helper function, it also removes it.
Signed-off-by: Calvin Owens <calvinowens@fb.com>
---
fs/proc/base.c | 47 ++++++++++++++++++++++++++---------------------
1 file changed, 26 insertions(+), 21 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 3f3d7ae..308fcbd 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -485,23 +485,6 @@ static int proc_pid_syscall(struct seq_file *m, struct pid_namespace *ns,
/* Here the fs part begins */
/************************************************************************/
-/* permission checks */
-static int proc_fd_access_allowed(struct inode *inode)
-{
- struct task_struct *task;
- int allowed = 0;
- /* Allow access to a task's file descriptors if it is us or we
- * may use ptrace attach to the process and find out that
- * information.
- */
- task = get_proc_task(inode);
- if (task) {
- allowed = ptrace_may_access(task, PTRACE_MODE_READ);
- put_task_struct(task);
- }
- return allowed;
-}
-
int proc_setattr(struct dentry *dentry, struct iattr *attr)
{
int error;
@@ -1375,10 +1358,21 @@ static void *proc_pid_follow_link(struct dentry *dentry, struct nameidata *nd)
{
struct inode *inode = dentry->d_inode;
struct path path;
- int error = -EACCES;
+ int error = -ESRCH;
+ int allowed = 0;
+ struct task_struct *task;
/* Are we allowed to snoop on the tasks file descriptors? */
- if (!proc_fd_access_allowed(inode))
+ task = get_proc_task(inode);
+ if (task) {
+ allowed = ptrace_may_access(task, PTRACE_MODE_READ);
+ put_task_struct(task);
+ } else {
+ goto out;
+ }
+
+ error = -EACCES;
+ if (!allowed)
goto out;
error = PROC_I(inode)->op.proc_get_link(dentry, &path);
@@ -1417,12 +1411,23 @@ static int do_proc_readlink(struct path *path, char __user *buffer, int buflen)
static int proc_pid_readlink(struct dentry * dentry, char __user * buffer, int buflen)
{
- int error = -EACCES;
+ int error = -ESRCH;
+ int allowed = 0;
+ struct task_struct *task;
struct inode *inode = dentry->d_inode;
struct path path;
/* Are we allowed to snoop on the tasks file descriptors? */
- if (!proc_fd_access_allowed(inode))
+ task = get_proc_task(inode);
+ if (task) {
+ allowed = ptrace_may_access(task, PTRACE_MODE_READ);
+ put_task_struct(task);
+ } else {
+ goto out;
+ }
+
+ error = -EACCES;
+ if (!allowed)
goto out;
error = PROC_I(inode)->op.proc_get_link(dentry, &path);
--
1.8.1
next prev parent reply other threads:[~2015-02-14 20:45 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-14 0:20 [RFC][PATCH] procfs: Add /proc/<pid>/mapped_files Calvin Owens
2015-01-14 0:23 ` Calvin Owens
2015-01-14 14:13 ` Rasmus Villemoes
2015-01-14 14:37 ` Siddhesh Poyarekar
2015-01-14 14:53 ` Rasmus Villemoes
2015-01-14 21:03 ` Calvin Owens
2015-01-14 22:45 ` Andrew Morton
2015-01-14 23:51 ` Rasmus Villemoes
2015-01-16 1:15 ` Andrew Morton
2015-01-16 11:00 ` Kirill A. Shutemov
2015-01-14 15:25 ` Kirill A. Shutemov
2015-01-14 15:33 ` Cyrill Gorcunov
2015-01-14 20:46 ` Calvin Owens
2015-01-14 21:16 ` Cyrill Gorcunov
2015-01-22 2:45 ` [RFC][PATCH] procfs: Always expose /proc/<pid>/map_files/ and make it readable Calvin Owens
2015-01-22 7:16 ` Cyrill Gorcunov
2015-01-22 11:02 ` Kirill A. Shutemov
2015-01-22 21:00 ` Calvin Owens
2015-01-22 21:27 ` Kirill A. Shutemov
2015-01-23 5:52 ` Calvin Owens
2015-01-24 3:15 ` [RFC][PATCH v2] " Calvin Owens
2015-01-26 12:47 ` Kirill A. Shutemov
2015-01-26 21:00 ` Cyrill Gorcunov
2015-01-26 23:43 ` Andrew Morton
2015-01-27 0:15 ` Kees Cook
2015-01-27 7:37 ` Cyrill Gorcunov
2015-01-27 19:53 ` Kees Cook
2015-01-27 21:35 ` Cyrill Gorcunov
2015-01-27 21:46 ` Pavel Emelyanov
2015-01-27 0:19 ` Kirill A. Shutemov
2015-01-27 6:46 ` Cyrill Gorcunov
2015-01-27 6:50 ` Andrew Morton
2015-01-27 7:23 ` Cyrill Gorcunov
2015-01-28 4:38 ` Calvin Owens
2015-01-30 1:30 ` Kees Cook
2015-01-31 1:58 ` Calvin Owens
2015-02-02 14:01 ` Austin S Hemmelgarn
2015-02-04 3:53 ` Calvin Owens
2015-02-02 20:16 ` Andy Lutomirski
2015-02-04 3:28 ` Calvin Owens
2015-02-12 2:29 ` [RFC][PATCH v3] " Calvin Owens
2015-02-12 7:45 ` Cyrill Gorcunov
2015-02-14 20:40 ` [RFC][PATCH v4] " Calvin Owens
2015-03-10 22:17 ` Cyrill Gorcunov
2015-04-28 22:23 ` Calvin Owens
2015-04-29 7:32 ` Cyrill Gorcunov
2015-05-19 3:10 ` [PATCH v5] " Calvin Owens
2015-05-19 3:29 ` Joe Perches
2015-05-19 18:04 ` Andy Lutomirski
2015-05-21 1:52 ` Calvin Owens
2015-05-21 2:10 ` Andy Lutomirski
2015-06-09 3:39 ` [PATCH v6] " Calvin Owens
2015-06-09 17:27 ` Kees Cook
2015-06-09 17:47 ` Andy Lutomirski
2015-06-09 18:15 ` Cyrill Gorcunov
2015-06-09 21:13 ` Andrew Morton
2015-06-10 1:39 ` Calvin Owens
2015-06-10 20:58 ` Andrew Morton
2015-06-11 11:10 ` Alexey Dobriyan
2015-06-11 18:49 ` Andrew Morton
2015-06-12 9:55 ` Alexey Dobriyan
2015-06-19 2:32 ` [PATCH v7] " Calvin Owens
2015-07-15 22:21 ` Andrew Morton
2015-07-15 23:39 ` Calvin Owens
2015-02-14 20:44 ` Calvin Owens [this message]
2015-01-14 22:40 ` [RFC][PATCH] procfs: Add /proc/<pid>/mapped_files Kirill A. Shutemov
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