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ecryptfs: forbid opening files without mmap handler

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

Change-Id: I91f0a2b4fecaa7deaef9d5b062dca1b88a083703
Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Tyler Hicks <tyhicks@canonical.com>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Git-repo: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git
Git-commit: 2f36db71009304b3f0b95afacd8eba1f9f046b87
Signed-off-by: Ravi Kumar Siddojigari <rsiddoji@codeaurora.org>
This commit is contained in:
Jann Horn 2016-09-07 21:36:57 +05:30 committed by Gerrit - the friendly Code Review server
parent ef2585bf91
commit 5076566ad5
1 changed files with 12 additions and 2 deletions
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14
fs/ecryptfs/kthread.c
View file

@ -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(lower_dentry->d_inode) ? 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 +166,17 @@ 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;
}