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tomoyo: Don't use nifty names on sockets.

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syzbot is reporting that use of SOCKET_I()->sk from open() can result in
use after free problem [1], for socket's inode is still reachable via
/proc/pid/fd/n despite destruction of SOCKET_I()->sk already completed.

At first I thought that this race condition applies to only open/getattr
permission checks. But James Morris has pointed out that there are more
permission checks where this race condition applies to. Thus, get rid of
tomoyo_get_socket_name() instead of conditionally bypassing permission
checks on sockets. As a side effect of this patch,
"socket:[family=\$:type=\$:protocol=\$]" in the policy files has to be
rewritten to "socket:[\$]".

[1] https://syzkaller.appspot.com/bug?id=73d590010454403d55164cca23bd0565b1eb3b74

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: syzbot <syzbot+0341f6a4d729d4e0acf1@syzkaller.appspotmail.com>
Reported-by: James Morris <jmorris@namei.org>
This commit is contained in:
Tetsuo Handa 2019-11-25 10:46:51 +09:00
parent 6794862a16
commit 6f7c41374b
1 changed files with 1 additions and 31 deletions
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32
security/tomoyo/realpath.c
View File

@ -217,31 +217,6 @@ out:
return ERR_PTR(-ENOMEM);
}
/**
* tomoyo_get_socket_name - Get the name of a socket.
*
* @path: Pointer to "struct path".
* @buffer: Pointer to buffer to return value in.
* @buflen: Sizeof @buffer.
*
* Returns the buffer.
*/
static char *tomoyo_get_socket_name(const struct path *path, char * const buffer,
const int buflen)
{
struct inode *inode = d_backing_inode(path->dentry);
struct socket *sock = inode ? SOCKET_I(inode) : NULL;
struct sock *sk = sock ? sock->sk : NULL;
if (sk) {
snprintf(buffer, buflen, "socket:[family=%u:type=%u:protocol=%u]",
sk->sk_family, sk->sk_type, sk->sk_protocol);
} else {
snprintf(buffer, buflen, "socket:[unknown]");
}
return buffer;
}
/**
* tomoyo_realpath_from_path - Returns realpath(3) of the given pathname but ignores chroot'ed root.
*
@ -279,12 +254,7 @@ char *tomoyo_realpath_from_path(const struct path *path)
break;
/* To make sure that pos is '\0' terminated. */
buf[buf_len - 1] = '\0';
/* Get better name for socket. */
if (sb->s_magic == SOCKFS_MAGIC) {
pos = tomoyo_get_socket_name(path, buf, buf_len - 1);
goto encode;
}
/* For "pipe:[\$]". */
/* For "pipe:[\$]" and "socket:[\$]". */
if (dentry->d_op && dentry->d_op->d_dname) {
pos = dentry->d_op->d_dname(dentry, buf, buf_len - 1);
goto encode;