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Message-ID: <20110804162009.GA2469@albatros>
Date: Thu, 4 Aug 2011 20:20:09 +0400
From: Vasiliy Kulikov <segoon@...nwall.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: kernel-hardening@...ts.openwall.com,
Al Viro <viro@...iv.linux.org.uk>,
David Rientjes <rientjes@...gle.com>,
Stephen Wilson <wilsons@...rt.ca>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
linux-kernel@...r.kernel.org, security@...nel.org
Subject: [PATCH] proc: fix races of /proc/PID/{fd/,fdinfo/,fdinfo/*}
fd* files are restricted to the task's owner, but keeping opened procfs
file descriptors makes it possible to violate the permission model.
Keeping fdinfo/* may disclosure current position and flags, keeping
fdinfo/ and fd/ may disclosure number of opened files.
Used existing (un)lock_trace functions to deal with the race.
CC: Stable Tree <stable@...nel.org>
Signed-off-by: Vasiliy Kulikov <segoon@...nwall.com>
---
Hopefully, I'll propose more simple way to guard private procfs files
soon, without these "scattered" ptrace checks.
fs/proc/base.c | 86 +++++++++++++++++++++++++++++++++++--------------------
1 files changed, 55 insertions(+), 31 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 08e3ecc..b0477c3 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1906,37 +1906,46 @@ static int proc_fd_info(struct inode *inode, struct path *path, char *info)
struct files_struct *files = NULL;
struct file *file;
int fd = proc_fd(inode);
+ int rc;
- if (task) {
- files = get_files_struct(task);
- put_task_struct(task);
- }
- if (files) {
- /*
- * We are not taking a ref to the file structure, so we must
- * hold ->file_lock.
- */
- spin_lock(&files->file_lock);
- file = fcheck_files(files, fd);
- if (file) {
- if (path) {
- *path = file->f_path;
- path_get(&file->f_path);
- }
- if (info)
- snprintf(info, PROC_FDINFO_MAX,
- "pos:\t%lli\n"
- "flags:\t0%o\n",
- (long long) file->f_pos,
- file->f_flags);
- spin_unlock(&files->file_lock);
- put_files_struct(files);
- return 0;
+ if (!task)
+ return -ESRCH;
+
+ rc = lock_trace(task);
+ if (rc)
+ goto out_task;
+
+ files = get_files_struct(task);
+ if (files == NULL)
+ goto out_unlock;
+ /*
+ * We are not taking a ref to the file structure, so we must
+ * hold ->file_lock.
+ */
+ spin_lock(&files->file_lock);
+ file = fcheck_files(files, fd);
+ if (file) {
+ if (path) {
+ *path = file->f_path;
+ path_get(&file->f_path);
}
- spin_unlock(&files->file_lock);
- put_files_struct(files);
+ if (info)
+ snprintf(info, PROC_FDINFO_MAX,
+ "pos:\t%lli\n"
+ "flags:\t0%o\n",
+ (long long) file->f_pos,
+ file->f_flags);
+ rc = 0;
+ } else {
+ rc = -ENOENT;
}
- return -ENOENT;
+ spin_unlock(&files->file_lock);
+ put_files_struct(files);
+out_unlock:
+ unlock_trace(task);
+out_task:
+ put_task_struct(task);
+ return rc;
}
static int proc_fd_link(struct inode *inode, struct path *path)
@@ -2057,13 +2066,20 @@ static struct dentry *proc_lookupfd_common(struct inode *dir,
struct task_struct *task = get_proc_task(dir);
unsigned fd = name_to_int(dentry);
struct dentry *result = ERR_PTR(-ENOENT);
+ int rc;
if (!task)
goto out_no_task;
if (fd == ~0U)
goto out;
+ rc = lock_trace(task);
+ result = ERR_PTR(rc);
+ if (rc)
+ goto out;
+
result = instantiate(dir, dentry, task, &fd);
+ unlock_trace(task);
out:
put_task_struct(task);
out_no_task:
@@ -2083,23 +2099,28 @@ static int proc_readfd_common(struct file * filp, void * dirent,
retval = -ENOENT;
if (!p)
goto out_no_task;
+
+ retval = lock_trace(p);
+ if (retval)
+ goto out;
+
retval = 0;
fd = filp->f_pos;
switch (fd) {
case 0:
if (filldir(dirent, ".", 1, 0, inode->i_ino, DT_DIR) < 0)
- goto out;
+ goto out_unlock;
filp->f_pos++;
case 1:
ino = parent_ino(dentry);
if (filldir(dirent, "..", 2, 1, ino, DT_DIR) < 0)
- goto out;
+ goto out_unlock;
filp->f_pos++;
default:
files = get_files_struct(p);
if (!files)
- goto out;
+ goto out_unlock;
rcu_read_lock();
for (fd = filp->f_pos-2;
fd < files_fdtable(files)->max_fds;
@@ -2123,6 +2144,9 @@ static int proc_readfd_common(struct file * filp, void * dirent,
rcu_read_unlock();
put_files_struct(files);
}
+
+out_unlock:
+ unlock_trace(p);
out:
put_task_struct(p);
out_no_task:
--
1.7.0.4
--
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