Messages in this thread | | | Date | Sun, 18 Mar 2012 18:45:47 +0000 | From | Al Viro <> | Subject | Re: races in ipathfs |
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On Thu, Jan 19, 2012 at 08:20:04PM +0000, Al Viro wrote: > Use of qib_super is seriously racy. qibfs_add() (and worse, > qibfs_remove()) can happen during qibfs_mount() and qibfs_kill_super().
[snip]
FWIW, I've put a completely untested patchset into git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git qibfs
It tries to avoid that kind of crap by getting rid of "populate at mount time" logics - we keep (internal) mount of that sucker for as long as there are any devices owned by ib_qib, adding them on add_device() and removing on remove_device(). The only complication is with module use counts - that fs has to be a separate module, or we'll have ib_qib impossible to rmmod, because fs keeps its module pinned and any devices held by ib_qib PCI driver will keep the fs pinned, so we never get to unregistering said PCI driver. With skeleton of qibfs (static parts only) taken to ib_qib_fs.c we avoid that problem - it is what ends up being pinned down for as long as ib_qib owns any devices, but then it's pinned down by ib_qib using exports from ib_qib_fs anyway. And once ib_qib is removed, all internal references to that vfsmount and superblock disappear as well...
This stuff is completely untested; I don't have the hardware in question. It does compile and survive modpost, but that's it. Please, review and comment...
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