From: Kees Cook <keescook@chromium.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Kees Cook <keescook@chromium.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Aleksa Sarai <cyphar@cyphar.com>,
Christian Brauner <christian.brauner@ubuntu.com>,
Dmitry Vyukov <dvyukov@google.com>,
Eric Biggers <ebiggers3@gmail.com>,
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2 3/3] exec: Move path_noexec() check earlier
Date: Fri, 5 Jun 2020 09:00:13 -0700 [thread overview]
Message-ID: <20200605160013.3954297-4-keescook@chromium.org> (raw)
In-Reply-To: <20200605160013.3954297-1-keescook@chromium.org>
The path_noexec() check, like the regular file check, was happening too
late, letting LSMs see impossible execve()s. Check it earlier as well
in may_open() and collect the redundant fs/exec.c path_noexec() test
under the same robustness comment as the S_ISREG() check.
My notes on the call path, and related arguments, checks, etc:
do_open_execat()
struct open_flags open_exec_flags = {
.open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
.acc_mode = MAY_EXEC,
...
do_filp_open(dfd, filename, open_flags)
path_openat(nameidata, open_flags, flags)
file = alloc_empty_file(open_flags, current_cred());
do_open(nameidata, file, open_flags)
may_open(path, acc_mode, open_flag)
/* new location of MAY_EXEC vs path_noexec() test */
inode_permission(inode, MAY_OPEN | acc_mode)
security_inode_permission(inode, acc_mode)
vfs_open(path, file)
do_dentry_open(file, path->dentry->d_inode, open)
security_file_open(f)
open()
/* old location of path_noexec() test */
Signed-off-by: Kees Cook <keescook@chromium.org>
---
fs/exec.c | 12 ++++--------
fs/namei.c | 4 ++++
2 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c
index 2b708629dcd6..7ac50a260df3 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -145,10 +145,8 @@ SYSCALL_DEFINE1(uselib, const char __user *, library)
* and check again at the very end too.
*/
error = -EACCES;
- if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode)))
- goto exit;
-
- if (path_noexec(&file->f_path))
+ if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode) ||
+ path_noexec(&file->f_path)))
goto exit;
fsnotify_open(file);
@@ -871,10 +869,8 @@ static struct file *do_open_execat(int fd, struct filename *name, int flags)
* and check again at the very end too.
*/
err = -EACCES;
- if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode)))
- goto exit;
-
- if (path_noexec(&file->f_path))
+ if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode) ||
+ path_noexec(&file->f_path)))
goto exit;
err = deny_write_access(file);
diff --git a/fs/namei.c b/fs/namei.c
index 0a759b68d66e..41e6fed8ce69 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2849,6 +2849,10 @@ static int may_open(const struct path *path, int acc_mode, int flag)
return -EACCES;
flag &= ~O_TRUNC;
break;
+ case S_IFREG:
+ if ((acc_mode & MAY_EXEC) && path_noexec(path))
+ return -EACCES;
+ break;
}
error = inode_permission(inode, MAY_OPEN | acc_mode);
--
2.25.1
next prev parent reply other threads:[~2020-06-05 16:00 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-05 16:00 [PATCH v2 0/3] Relocate execve() sanity checks Kees Cook
2020-06-05 16:00 ` [PATCH v2 1/3] exec: Change uselib(2) IS_SREG() failure to EACCES Kees Cook
2020-06-05 16:00 ` [PATCH v2 2/3] exec: Move S_ISREG() check earlier Kees Cook
2020-08-13 14:13 ` Marc Zyngier
2020-08-13 17:13 ` Kees Cook
2020-06-05 16:00 ` Kees Cook [this message]
2020-06-06 0:40 ` [PATCH v2 0/3] Relocate execve() sanity checks Andrew Morton
2020-06-06 1:45 ` Kees Cook
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