ipc: convert do_mq_open() to FD_ADD()

Christian Brauner <brauner@kernel.org> says:

The fix sent in [1] was squashed into this commit.

Fixes: https://lore.kernel.org/c41de645-8234-465f-a3be-f0385e3a163c@sirena.org.uk [1]
Reported-by: Mark Brown <broonie@kernel.org> [1]
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> [1]
Link: https://patch.msgid.link/20251123-work-fd-prepare-v4-22-b6efa1706cfd@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index 093551fe66a7eb884fc34ef853a0ca92b95770af..d3a588d0dcf618ee3aa4b232cad16c8d1955076e 100644 (file)
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -892,14 +892,35 @@ static int prepare_open(struct dentry *dentry, int oflag, int ro,
        return inode_permission(&nop_mnt_idmap, d_inode(dentry), acc);
 }
 
+static struct file *mqueue_file_open(struct filename *name,
+                                    struct vfsmount *mnt, int oflag, bool ro,
+                                    umode_t mode, struct mq_attr *attr)
+{
+       struct path path __free(path_put) = {};
+       struct dentry *dentry;
+       int ret;
+
+       dentry = lookup_noperm(&QSTR(name->name), mnt->mnt_root);
+       if (IS_ERR(dentry))
+               return ERR_CAST(dentry);
+
+       path.dentry = dentry;
+       path.mnt = mntget(mnt);
+
+       ret = prepare_open(path.dentry, oflag, ro, mode, name, attr);
+       if (ret)
+               return ERR_PTR(ret);
+
+       return dentry_open(&path, oflag, current_cred());
+}
+
 static int do_mq_open(const char __user *u_name, int oflag, umode_t mode,
                      struct mq_attr *attr)
 {
+       struct filename *name __free(putname) = NULL;;
        struct vfsmount *mnt = current->nsproxy->ipc_ns->mq_mnt;
        struct dentry *root = mnt->mnt_root;
-       struct filename *name;
-       struct path path;
-       int fd, error;
+       int fd;
        int ro;
 
        audit_mq_open(oflag, mode, attr);
@@ -908,37 +929,12 @@ static int do_mq_open(const char __user *u_name, int oflag, umode_t mode,
        if (IS_ERR(name))
                return PTR_ERR(name);
 
-       fd = get_unused_fd_flags(O_CLOEXEC);
-       if (fd < 0)
-               goto out_putname;
-
        ro = mnt_want_write(mnt);       /* we'll drop it in any case */
        inode_lock(d_inode(root));
-       path.dentry = lookup_noperm(&QSTR(name->name), root);
-       if (IS_ERR(path.dentry)) {
-               error = PTR_ERR(path.dentry);
-               goto out_putfd;
-       }
-       path.mnt = mntget(mnt);
-       error = prepare_open(path.dentry, oflag, ro, mode, name, attr);
-       if (!error) {
-               struct file *file = dentry_open(&path, oflag, current_cred());
-               if (!IS_ERR(file))
-                       fd_install(fd, file);
-               else
-                       error = PTR_ERR(file);
-       }
-       path_put(&path);
-out_putfd:
-       if (error) {
-               put_unused_fd(fd);
-               fd = error;
-       }
+       fd = FD_ADD(O_CLOEXEC, mqueue_file_open(name, mnt, oflag, ro, mode, attr));
        inode_unlock(d_inode(root));
        if (!ro)
                mnt_drop_write(mnt);
-out_putname:
-       putname(name);
        return fd;
 }