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dkim=pass header.d=oracle.com header.s=corp-2021-07-09 header.b=roSc1gFB; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b=A9dGXvL2; spf=none (imf23.hostedemail.com: domain of mike.kravetz@oracle.com has no SPF policy when checking 205.220.165.32) smtp.mailfrom=mike.kravetz@oracle.com; dmarc=pass (policy=none) header.from=oracle.com X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 19DA8140002 X-HE-Tag: 1643049319-261015 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 1/23/22 20:18, Hugh Dickins wrote: > On Sat, 22 Jan 2022, Aleksa Sarai wrote: > >> Adding the maintainers of mm/{shmem,memfd}.c and fs/hugetlbfs/ just in >> case this was not intended behaviour. > > Kir is correct - thanks - and it is intended behaviour. Not consciously > intended to make for a difficult manpage, but the implementation was > intended to be simple, so tmpfs and hugetlbfs do not internally > distinguish memfd objects from filesystem files - their filesystem > files simply start off with F_SEAL_SEAL to rule out any sealing. > Thanks Hugh, I agree. >> On 2022-01-21, Kir Kolyshkin wrote: >>> Currently, from the description of file sealing it can be deduced that >>> unless the fd is a memfd, all sealing operations fail with EINVAL. >>> >>> Apparently, it's not true for tmpfs or hugetlbfs -- F_GET_SEALS returns >>> 1 (F_SEAL_SEAL) for an fd opened on these filesystems (probably because >>> those are used to back memfd files). >>> >>> Fix the description to mention that peculiarity. Not knowing this can >>> result in incorrect code logic (see [1], where the code mistook a >>> descriptor of a file opened on on tmpfs for a memfd). >>> >>> While at it, clarify that fcntl does not actually return EINVAL, but >>> sets errno to it (as it is usually said elsewhere). >>> >>> [1] https://github.com/opencontainers/runc/pull/3342 >>> >>> Cc: Aleksa Sarai >>> Cc: David Herrmann >>> Signed-off-by: Kir Kolyshkin > > Acked-by: Hugh Dickins Acked-by: Mike Kravetz -- Mike Kravetz