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ecryptfs: forbid opening files without mmap handler

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commit 2f36db7100 upstream.

This prevents users from triggering a stack overflow through a recursive
invocation of pagefault handling that involves mapping procfs files into
virtual memory.

Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jann Horn
2016-06-01 11:55:06 +02:00
committed by Greg Kroah-Hartman
parent d3f97524ef
commit dea2cf7c0c
1 changed files with 11 additions and 2 deletions
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13
fs/ecryptfs/kthread.c
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@@ -25,6 +25,7 @@
#include <linux/slab.h>
#include <linux/wait.h>
#include <linux/mount.h>
#include <linux/file.h>
#include "ecryptfs_kernel.h"
struct ecryptfs_open_req {
@@ -147,7 +148,7 @@ int ecryptfs_privileged_open(struct file **lower_file,
flags |= IS_RDONLY(d_inode(lower_dentry)) ? O_RDONLY : O_RDWR;
(*lower_file) = dentry_open(&req.path, flags, cred);
if (!IS_ERR(*lower_file))
goto out;
goto have_file;
if ((flags & O_ACCMODE) == O_RDONLY) {
rc = PTR_ERR((*lower_file));
goto out;
@@ -165,8 +166,16 @@ int ecryptfs_privileged_open(struct file **lower_file,
mutex_unlock(&ecryptfs_kthread_ctl.mux);
wake_up(&ecryptfs_kthread_ctl.wait);
wait_for_completion(&req.done);
if (IS_ERR(*lower_file))
if (IS_ERR(*lower_file)) {
rc = PTR_ERR(*lower_file);
goto out;
}
have_file:
if ((*lower_file)->f_op->mmap == NULL) {
fput(*lower_file);
*lower_file = NULL;
rc = -EMEDIUMTYPE;
}
out:
return rc;
}