user/sven/linux.git/fs/fcntl.c, branch v4.4

vfs: renumber FMODE_NONOTIFY and add to uniqueness check

2015-01-08T23:10:52Z

Fix clashing values for O_PATH and FMODE_NONOTIFY on sparc. The clashing O_PATH value was added in commit 5229645bdc35 ("vfs: add nonconflicting values for O_PATH") but this can't be changed as it is user-visible. FMODE_NONOTIFY is only used internally in the kernel, but it is in the same numbering space as the other O_* flags, as indicated by the comment at the top of include/uapi/asm-generic/fcntl.h (and its use in fs/notify/fanotify/fanotify_user.c). So renumber it to avoid the clash. All of this has happened before (commit 12ed2e36c98a: "fanotify: FMODE_NONOTIFY and __O_SYNC in sparc conflict"), and all of this will happen again -- so update the uniqueness check in fcntl_init() to include __FMODE_NONOTIFY. Signed-off-by: David Drysdale Acked-by: David S. Miller Acked-by: Jan Kara Cc: Heinrich Schuchardt Cc: Alexander Viro Cc: Arnd Bergmann Cc: Stephen Rothwell Cc: Eric Paris Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

security: make security_file_set_fowner, f_setown and __f_setown void return

2014-09-09T20:01:36Z

security_file_set_fowner always returns 0, so make it f_setown and __f_setown void return functions and fix up the error handling in the callers. Cc: linux-security-module@vger.kernel.org Signed-off-by: Jeff Layton Reviewed-by: Christoph Hellwig

shm: add sealing API

2014-08-08T22:57:31Z

If two processes share a common memory region, they usually want some guarantees to allow safe access. This often includes: - one side cannot overwrite data while the other reads it - one side cannot shrink the buffer while the other accesses it - one side cannot grow the buffer beyond previously set boundaries If there is a trust-relationship between both parties, there is no need for policy enforcement. However, if there's no trust relationship (eg., for general-purpose IPC) sharing memory-regions is highly fragile and often not possible without local copies. Look at the following two use-cases: 1) A graphics client wants to share its rendering-buffer with a graphics-server. The memory-region is allocated by the client for read/write access and a second FD is passed to the server. While scanning out from the memory region, the server has no guarantee that the client doesn't shrink the buffer at any time, requiring rather cumbersome SIGBUS handling. 2) A process wants to perform an RPC on another process. To avoid huge bandwidth consumption, zero-copy is preferred. After a message is assembled in-memory and a FD is passed to the remote side, both sides want to be sure that neither modifies this shared copy, anymore. The source may have put sensible data into the message without a separate copy and the target may want to parse the message inline, to avoid a local copy. While SIGBUS handling, POSIX mandatory locking and MAP_DENYWRITE provide ways to achieve most of this, the first one is unproportionally ugly to use in libraries and the latter two are broken/racy or even disabled due to denial of service attacks. This patch introduces the concept of SEALING. If you seal a file, a specific set of operations is blocked on that file forever. Unlike locks, seals can only be set, never removed. Hence, once you verified a specific set of seals is set, you're guaranteed that no-one can perform the blocked operations on this file, anymore. An initial set of SEALS is introduced by this patch: - SHRINK: If SEAL_SHRINK is set, the file in question cannot be reduced in size. This affects ftruncate() and open(O_TRUNC). - GROW: If SEAL_GROW is set, the file in question cannot be increased in size. This affects ftruncate(), fallocate() and write(). - WRITE: If SEAL_WRITE is set, no write operations (besides resizing) are possible. This affects fallocate(PUNCH_HOLE), mmap() and write(). - SEAL: If SEAL_SEAL is set, no further seals can be added to a file. This basically prevents the F_ADD_SEAL operation on a file and can be set to prevent others from adding further seals that you don't want. The described use-cases can easily use these seals to provide safe use without any trust-relationship: 1) The graphics server can verify that a passed file-descriptor has SEAL_SHRINK set. This allows safe scanout, while the client is allowed to increase buffer size for window-resizing on-the-fly. Concurrent writes are explicitly allowed. 2) For general-purpose IPC, both processes can verify that SEAL_SHRINK, SEAL_GROW and SEAL_WRITE are set. This guarantees that neither process can modify the data while the other side parses it. Furthermore, it guarantees that even with writable FDs passed to the peer, it cannot increase the size to hit memory-limits of the source process (in case the file-storage is accounted to the source). The new API is an extension to fcntl(), adding two new commands: F_GET_SEALS: Return a bitset describing the seals on the file. This can be called on any FD if the underlying file supports sealing. F_ADD_SEALS: Change the seals of a given file. This requires WRITE access to the file and F_SEAL_SEAL may not already be set. Furthermore, the underlying file must support sealing and there may not be any existing shared mapping of that file. Otherwise, EBADF/EPERM is returned. The given seals are _added_ to the existing set of seals on the file. You cannot remove seals again. The fcntl() handler is currently specific to shmem and disabled on all files. A file needs to explicitly support sealing for this interface to work. A separate syscall is added in a follow-up, which creates files that support sealing. There is no intention to support this on other file-systems. Semantics are unclear for non-volatile files and we lack any use-case right now. Therefore, the implementation is specific to shmem. Signed-off-by: David Herrmann Acked-by: Hugh Dickins Cc: Michael Kerrisk Cc: Ryan Lortie Cc: Lennart Poettering Cc: Daniel Mack Cc: Andy Lutomirski Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

locks: rename file-private locks to "open file description locks"

2014-04-22T12:23:58Z

File-private locks have been merged into Linux for v3.15, and *now* people are commenting that the name and macro definitions for the new file-private locks suck. ...and I can't even disagree. The names and command macros do suck. We're going to have to live with these for a long time, so it's important that we be happy with the names before we're stuck with them. The consensus on the lists so far is that they should be rechristened as "open file description locks". The name isn't a big deal for the kernel, but the command macros are not visually distinct enough from the traditional POSIX lock macros. The glibc and documentation folks are recommending that we change them to look like F_OFD_{GETLK|SETLK|SETLKW}. That lessens the chance that a programmer will typo one of the commands wrong, and also makes it easier to spot this difference when reading code. This patch makes the following changes that I think are necessary before v3.15 ships: 1) rename the command macros to their new names. These end up in the uapi headers and so are part of the external-facing API. It turns out that glibc doesn't actually use the fcntl.h uapi header, but it's hard to be sure that something else won't. Changing it now is safest. 2) make the the /proc/locks output display these as type "OFDLCK" Cc: Michael Kerrisk Cc: Christoph Hellwig Cc: Carlos O'Donell Cc: Stefan Metzmacher Cc: Andy Lutomirski Cc: Frank Filz Cc: Theodore Ts'o Signed-off-by: Jeff Layton

locks: add new fcntl cmd values for handling file private locks

2014-03-31T12:24:43Z

Due to some unfortunate history, POSIX locks have very strange and unhelpful semantics. The thing that usually catches people by surprise is that they are dropped whenever the process closes any file descriptor associated with the inode. This is extremely problematic for people developing file servers that need to implement byte-range locks. Developers often need a "lock management" facility to ensure that file descriptors are not closed until all of the locks associated with the inode are finished. Additionally, "classic" POSIX locks are owned by the process. Locks taken between threads within the same process won't conflict with one another, which renders them useless for synchronization between threads. This patchset adds a new type of lock that attempts to address these issues. These locks conflict with classic POSIX read/write locks, but have semantics that are more like BSD locks with respect to inheritance and behavior on close. This is implemented primarily by changing how fl_owner field is set for these locks. Instead of having them owned by the files_struct of the process, they are instead owned by the filp on which they were acquired. Thus, they are inherited across fork() and are only released when the last reference to a filp is put. These new semantics prevent them from being merged with classic POSIX locks, even if they are acquired by the same process. These locks will also conflict with classic POSIX locks even if they are acquired by the same process or on the same file descriptor. The new locks are managed using a new set of cmd values to the fcntl() syscall. The initial implementation of this converts these values to "classic" cmd values at a fairly high level, and the details are not exposed to the underlying filesystem. We may eventually want to push this handing out to the lower filesystem code but for now I don't see any need for it. Also, note that with this implementation the new cmd values are only available via fcntl64() on 32-bit arches. There's little need to add support for legacy apps on a new interface like this. Signed-off-by: Jeff Layton

locks: pass the cmd value to fcntl_getlk/getlk64

2014-03-31T12:24:43Z

Once we introduce file private locks, we'll need to know what cmd value was used, as that affects the ownership and whether a conflict would arise. Signed-off-by: Jeff Layton

file->f_op is never NULL...

2013-10-25T03:34:54Z

Signed-off-by: Al Viro

vfs: add missing check for __O_TMPFILE in fcntl_init()

2013-08-05T14:25:32Z

As comment in include/uapi/asm-generic/fcntl.h described, when introducing new O_* bits, we need to check its uniqueness in fcntl_init(). But __O_TMPFILE bit is missing. So fix it. Signed-off-by: Zheng Liu Signed-off-by: Al Viro

new helper: file_inode(file)

2013-02-23T04:31:31Z

Signed-off-by: Al Viro

Fix F_DUPFD_CLOEXEC breakage

2012-10-09T06:52:31Z

Fix a braino in F_DUPFD_CLOEXEC; f_dupfd() expects flags for alloc_fd(), get_unused_fd() etc and there clone-on-exec if O_CLOEXEC, not FD_CLOEXEC. Reported-by: Richard W.M. Jones Signed-off-by: Al Viro Signed-off-by: Linus Torvalds