Messages in this thread | | | Subject | Re: [PATCH v2 3/7] fuse: Fix infinite loop in sget_fc() | From | Max Reitz <> | Date | Tue, 8 Jun 2021 17:12:15 +0200 |
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On 04.06.21 18:11, Greg Kurz wrote: > We don't set the SB_BORN flag on submounts. This is wrong as these > superblocks are then considered as partially constructed or dying > in the rest of the code and can break some assumptions. > > One such case is when you have a virtiofs filesystem with submounts > and you try to mount it again : virtio_fs_get_tree() tries to obtain > a superblock with sget_fc(). The logic in sget_fc() is to loop until > it has either found an existing matching superblock with SB_BORN set > or to create a brand new one. It is assumed that a superblock without > SB_BORN is transient and the loop is restarted. Forgetting to set > SB_BORN on submounts hence causes sget_fc() to retry forever. > > Setting SB_BORN requires special care, i.e. a write barrier for > super_cache_count() which can check SB_BORN without taking any lock. > We should call vfs_get_tree() to deal with that but this requires > to have a proper ->get_tree() implementation for submounts, which > is a bigger piece of work. Go for a simple bug fix in the meatime. > > Fixes: bf109c64040f ("fuse: implement crossmounts") > Cc: mreitz@redhat.com > Cc: stable@vger.kernel.org # v5.10+ > Signed-off-by: Greg Kurz <groug@kaod.org> > --- > fs/fuse/dir.c | 11 +++++++++++ > 1 file changed, 11 insertions(+)
Reviewed-by: Max Reitz <mreitz@redhat.com>
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