Hi,
Macro get_unused_fd() is a shortcut to call function get_unused_fd_flags(),
to allocate a file descriptor.
The macro use 0 as flags, so the file descriptor is created
without O_CLOEXEC flag.
This can be seen as an unsafe default eg. in most case O_CLOEXEC
must be used to not leak file descriptor across exec().
Newer kernel code should use anon_inode_getfd() or get_unused_fd_flags()
with flags provided by userspace. If flags cannot be given by userspace,
O_CLOEXEC must be the default flag.
Using O_CLOEXEC by default allows userspace to choose, without race,
if the file descriptor is going to be inherited across exec().
They are two ways to achieve this:
- makes get_unused_fd() use O_CLOEXEC by default
It's difficult to get it right: every code using of get_unused_fd()
must take this change into account and be fixed as soon as
macro get_unused_fd() do the switch. Non updated code will have
unexpected behavor and it's likely going to break API contract.
- remove get_unused_fd()
It's going to break some out of tree, not yet upstream kernel code,
but it's easy to notice and fix. Anyway, newer code should use
anon_inode_getfd() or get_unused_fd_flags().
The latter option was choosen to ensure no unexpected behavor
for out of tree, not yet upstream code. Removing the macro is the safest
choice: it's better to break build than trying to make get_unused_fd()
use O_CLOEXEC by default and get all user of get_unused_fd() update.
Additionnaly, removing the macro is not going to break modules ABI.
In linux-next tag 20130815, they're currently:
- 19 calls to get_unused_fd_flags() (+4)
not counting get_unused_fd() and anon_inode_getfd()
- 10 calls to get_unused_fd() (-4)
- 11 calls to anon_inode_getfd() (0)
The following patchset try to convert all calls to get_unused_fd()
to get_unused_fd_flags(0) before removing get_unused_fd() macro.
Without get_unused_fd() macro, more subsystems are likely to use
anon_inode_getfd() and be teached to provide an API that let userspace
choose the opening flags of the file descriptor.
Changes from v1 <http://lkml.kernel.org/r/cover.1372777600.git.ydroneaud@xxxxxxxxxx>:
- explicitly added subsystem maintainers as mail recepients.
- infiniband: use get_unused_fd_flags(0) instead of get_unused_fd()
DROPPED: subsystem maintainer applied another patch using
get_unused_fd_flags(O_CLOEXEC) as suggested.
- android/sw_sync: use get_unused_fd_flags(0) instead of get_unused_fd()
MODIFIED: use get_unused_fd_flags(O_CLOEXEC) as suggested by
<http://lkml.kernel.org/r/CACSP8SjXGMk2_kX_+RgzqqQwqKernvF1Wt3K5tw991W5dfAnCA@xxxxxxxxxxxxxx>
- android/sync: use get_unused_fd_flags(0) instead of get_unused_fd()
MODIFIED: use get_unused_fd_flags(O_CLOEXEC) as suggested by
<http://lkml.kernel.org/r/CACSP8SjZcpcpEtQHzcGYhf-MP7QGo0XpN7-uN7rmD=vNtopG=w@xxxxxxxxxxxxxx>
- xfs: use get_unused_fd_flags(0) instead of get_unused_fd()
DROPPED: applied asis by subsystem maintainer.
- sctp: use get_unused_fd_flags(0) instead of get_unused_fd()
DROPPED: applied asis by subsystem maintainer.
Yann Droneaud (10):
ia64: use get_unused_fd_flags(0) instead of get_unused_fd()
ppc/cell: use get_unused_fd_flags(0) instead of get_unused_fd()
android/sw_sync: use get_unused_fd_flags(O_CLOEXEC) instead of
get_unused_fd()
android/sync: use get_unused_fd_flags(O_CLOEXEC) instead of
get_unused_fd()
vfio: use get_unused_fd_flags(0) instead of get_unused_fd()
binfmt_misc: use get_unused_fd_flags(0) instead of get_unused_fd()
file: use get_unused_fd_flags(0) instead of get_unused_fd()
fanotify: use get_unused_fd_flags(0) instead of get_unused_fd()
events: use get_unused_fd_flags(0) instead of get_unused_fd()
file: remove get_unused_fd()
arch/ia64/kernel/perfmon.c | 2 +-
arch/powerpc/platforms/cell/spufs/inode.c | 4 ++--
drivers/staging/android/sw_sync.c | 2 +-
drivers/staging/android/sync.c | 2 +-
drivers/vfio/vfio.c | 2 +-
fs/binfmt_misc.c | 2 +-
fs/file.c | 2 +-
fs/notify/fanotify/fanotify_user.c | 2 +-
include/linux/file.h | 1 -
kernel/events/core.c | 2 +-
10 files changed, 10 insertions(+), 11 deletions(-)
--
1.8.3.1
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