lkml.org 
[lkml]   [2021]   [Feb]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 7/8] unix_bind_bsd(): unlink if we fail after successful mknod
Date
We can do that more or less safely, since the parent is
held locked all along. Yes, somebody might observe the
object via dcache, only to have it disappear afterwards,
but there's really no good way to prevent that. It won't
race with other bind(2) or attempts to move the sucker
elsewhere, or put something else in its place - locked
parent prevents that.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
net/unix/af_unix.c | 30 ++++++++++++++++--------------
1 file changed, 16 insertions(+), 14 deletions(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 368376621111..8bbdcddbf598 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1000,27 +1000,19 @@ static int unix_bind_bsd(struct sock *sk, struct unix_address *addr)
dentry = kern_path_create(AT_FDCWD, addr->name->sun_path, &parent, 0);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
-
/*
* All right, let's create it.
*/
err = security_path_mknod(&parent, dentry, mode, 0);
if (!err)
err = vfs_mknod(d_inode(parent.dentry), dentry, mode, 0);
- if (err) {
- done_path_create(&parent, dentry);
- return err;
- }
+ if (err)
+ goto out;
err = mutex_lock_interruptible(&u->bindlock);
- if (err) {
- done_path_create(&parent, dentry);
- return err;
- }
- if (u->addr) {
- mutex_unlock(&u->bindlock);
- done_path_create(&parent, dentry);
- return -EINVAL;
- }
+ if (err)
+ goto out_unlink;
+ if (u->addr)
+ goto out_unlock;

addr->hash = UNIX_HASH_SIZE;
hash = d_backing_inode(dentry)->i_ino & (UNIX_HASH_SIZE - 1);
@@ -1032,6 +1024,16 @@ static int unix_bind_bsd(struct sock *sk, struct unix_address *addr)
mutex_unlock(&u->bindlock);
done_path_create(&parent, dentry);
return 0;
+
+out_unlock:
+ mutex_unlock(&u->bindlock);
+ err = -EINVAL;
+out_unlink:
+ /* failed after successful mknod? unlink what we'd created... */
+ vfs_unlink(d_inode(parent.dentry), dentry, NULL);
+out:
+ done_path_create(&parent, dentry);
+ return err;
}

static int unix_bind_abstract(struct sock *sk, unsigned hash,
--
2.11.0
\
 
 \ /
  Last update: 2021-02-22 20:21    [W:0.077 / U:2.400 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site