From: "J. Bruce Fields" <bfields@xxxxxxxxxx> A fuzzer recently triggered lockdep warnings about potential sb_writers deadlocks caused by fh_want_write, showing that we haven't been careful to pair each fh_want_write() with an fh_drop_write(). This isn't normally a problem since fh_put() will call fh_drop_write() for us. And that's OK for NFSv3. But an NFSv4 protocol fuzzer can do weird things like call unlink twice in a compound. So we can either make it safe to call fh_want_write() twice, or we can fix all the callers to call fh_drop_write(). For now I think we have to do the former just to get the bug fixed. Long term I don't know whether it's best to stay with that or to fix up the callers. I fixed nfsd_unlink just because it's easy, but maybe that's pointless, it's others (like setattr) that are the complicated ones. J. Bruce Fields (2): nfsd: allow fh_want_write to be called twice nfsd: fh_drop_write in nfsd_unlink fs/nfsd/vfs.c | 8 +++++--- fs/nfsd/vfs.h | 5 ++++- 2 files changed, 9 insertions(+), 4 deletions(-) -- 2.21.0
