d92d88f056
If fuse_fill_super_submount() returns an error, the error path
triggers a crash:
[ 26.206673] BUG: kernel NULL pointer dereference, address: 0000000000000000
[...]
[ 26.226362] RIP: 0010:__list_del_entry_valid+0x25/0x90
[...]
[ 26.247938] Call Trace:
[ 26.248300] fuse_mount_remove+0x2c/0x70 [fuse]
[ 26.248892] virtio_kill_sb+0x22/0x160 [virtiofs]
[ 26.249487] deactivate_locked_super+0x36/0xa0
[ 26.250077] fuse_dentry_automount+0x178/0x1a0 [fuse]
The crash happens because fuse_mount_remove() assumes that the FUSE
mount was already added to list under the FUSE connection, but this
only done after fuse_fill_super_submount() has returned success.
This means that until fuse_fill_super_submount() has returned success,
the FUSE mount isn't actually owned by the superblock. We should thus
reclaim ownership by clearing sb->s_fs_info, which will skip the call
to fuse_mount_remove(), and perform rollback, like virtio_fs_get_tree()
already does for the root sb.
Fixes: bf109c64040f ("fuse: implement crossmounts")
Cc: stable@vger.kernel.org # v5.10+
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.