diff options
| author | Cong Wang <xiyou.wangcong@gmail.com> | 2018-06-07 13:39:49 -0700 |
|---|---|---|
| committer | Chenbo Feng <fengc@google.com> | 2018-08-23 17:30:17 +0000 |
| commit | 3a2ec581f8e1b2f2ea949d4de42b99945cac5972 (patch) | |
| tree | e35e6496fa8b6c6af2c189358c0abfe0439fb128 /net | |
| parent | 37af2ff398acf2743e24d25a0ba20cfbf1c84d72 (diff) | |
UPSTREAM: socket: close race condition between sock_close() and sockfs_setattr()
fchownat() doesn't even hold refcnt of fd until it figures out
fd is really needed (otherwise is ignored) and releases it after
it resolves the path. This means sock_close() could race with
sockfs_setattr(), which leads to a NULL pointer dereference
since typically we set sock->sk to NULL in ->release().
As pointed out by Al, this is unique to sockfs. So we can fix this
in socket layer by acquiring inode_lock in sock_close() and
checking against NULL in sockfs_setattr().
sock_release() is called in many places, only the sock_close()
path matters here. And fortunately, this should not affect normal
sock_close() as it is only called when the last fd refcnt is gone.
It only affects sock_close() with a parallel sockfs_setattr() in
progress, which is not common.
Fixes: 86741ec25462 ("net: core: Add a UID field to struct sock.")
Reported-by: shankarapailoor <shankarapailoor@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Lorenzo Colitti <lorenzo@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 6d8c50dcb029872b298eea68cc6209c866fd3e14)
Signed-off-by: Chenbo Feng <fengc@google.com>
Bug: 112220999
Test: syzcaller reproducer doesn't trigger the crash anymore
Change-Id: I90bec1515889e0dfd23f94e3f29b366c7bbfcd11
Diffstat (limited to 'net')
| -rw-r--r-- | net/socket.c | 18 |
1 files changed, 15 insertions, 3 deletions
diff --git a/net/socket.c b/net/socket.c index b75a537807b5..b36c981d04dc 100644 --- a/net/socket.c +++ b/net/socket.c @@ -528,7 +528,10 @@ static int sockfs_setattr(struct dentry *dentry, struct iattr *iattr) if (!err && (iattr->ia_valid & ATTR_UID)) { struct socket *sock = SOCKET_I(d_inode(dentry)); - sock->sk->sk_uid = iattr->ia_uid; + if (sock->sk) + sock->sk->sk_uid = iattr->ia_uid; + else + err = -ENOENT; } return err; @@ -579,12 +582,16 @@ static struct socket *sock_alloc(void) * an inode not a file. */ -void sock_release(struct socket *sock) +static void __sock_release(struct socket *sock, struct inode *inode) { if (sock->ops) { struct module *owner = sock->ops->owner; + if (inode) + inode_lock(inode); sock->ops->release(sock); + if (inode) + inode_unlock(inode); sock->ops = NULL; module_put(owner); } @@ -599,6 +606,11 @@ void sock_release(struct socket *sock) } sock->file = NULL; } + +void sock_release(struct socket *sock) +{ + __sock_release(sock, NULL); +} EXPORT_SYMBOL(sock_release); void __sock_tx_timestamp(const struct sock *sk, __u8 *tx_flags) @@ -1035,7 +1047,7 @@ static int sock_mmap(struct file *file, struct vm_area_struct *vma) static int sock_close(struct inode *inode, struct file *filp) { - sock_release(SOCKET_I(inode)); + __sock_release(SOCKET_I(inode), inode); return 0; } |