Re: [PATCH] netfs: Fix UAF in netfs_unbuffered_write() on failed preparation

[David Howells]

This excerpt would seem to show how the problem comes about:

  a.out-717 : netfs_sreq: R=00000001[13] UPLD PREP  f=000 s=240000 0/0 s=192 e=0
  a.out-717 : netfs_sreq: R=00000001[13] UPLD SUBMT f=100 s=240000 0/20000 s=192 e=0
  a.out-717 : netfs_sreq: R=00000001[13] UPLD TERM  f=310 s=240000 1fac0/20000 s=160 e=0
  a.out-717 : netfs_rreq: R=00000001 UW WAKE-Q  f=1801
  a.out-717 : netfs_rreq: R=00000001 UW DONE-QUIESCE f=1801
  a.out-717 : netfs_sreq: R=00000001[13] UPLD RETRY f=210 s=240000 1fac0/20000 s=160 e=-11
  a.out-717 : netfs_sreq: R=00000001[13] UPLD SUBMT f=100 s=240000 0/dbfac0 s=192 e=0
  a.out-717 : netfs_failure: R=00000001[13] UPLD f=500 s=240000 0/dbfac0 write e=-5

It looks like there are two issues: firstly, why does the upload stop short?
Presumably that's forced by the test.  Secondly, I think it has miscalculated
the subreq size in the retry, hence the EIO.

David