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authorCong Wang <xiyou.wangcong@gmail.com>2018-06-07 23:39:49 +0300
committerDavid S. Miller <davem@davemloft.net>2018-06-10 22:25:53 +0300
commit6d8c50dcb029872b298eea68cc6209c866fd3e14 (patch)
tree4da75b8a914be8ad9bb1f8d81d0450ee8a4eb5b0
parent873aca2ee86e533665a73292c4e308ded1e9bafe (diff)
downloadlinux-6d8c50dcb029872b298eea68cc6209c866fd3e14.tar.xz
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>
-rw-r--r--net/socket.c18
1 files changed, 15 insertions, 3 deletions
diff --git a/net/socket.c b/net/socket.c
index af57d85bcb48..8a109012608a 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -541,7 +541,10 @@ 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;
@@ -590,12 +593,16 @@ EXPORT_SYMBOL(sock_alloc);
* 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);
}
@@ -609,6 +616,11 @@ 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(__u16 tsflags, __u8 *tx_flags)
@@ -1171,7 +1183,7 @@ 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;
}