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git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull 'struct fd' updates from Al Viro:
"Just the 'struct fd' layout change, with conversion to accessor
helpers"
* tag 'pull-stable-struct_fd' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
add struct fd constructors, get rid of __to_fd()
struct fd: representation change
introduce fd_file(), convert all accessors to it.
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull vfs mount updates from Christian Brauner:
"Recently, we added the ability to list mounts in other mount
namespaces and the ability to retrieve namespace file descriptors
without having to go through procfs by deriving them from pidfds.
This extends nsfs in two ways:
(1) Add the ability to retrieve information about a mount namespace
via NS_MNT_GET_INFO.
This will return the mount namespace id and the number of mounts
currently in the mount namespace. The number of mounts can be
used to size the buffer that needs to be used for listmount() and
is in general useful without having to actually iterate through
all the mounts.
The structure is extensible.
(2) Add the ability to iterate through all mount namespaces over
which the caller holds privilege returning the file descriptor
for the next or previous mount namespace.
To retrieve a mount namespace the caller must be privileged wrt
to it's owning user namespace. This means that PID 1 on the host
can list all mounts in all mount namespaces or that a container
can list all mounts of its nested containers.
Optionally pass a structure for NS_MNT_GET_INFO with
NS_MNT_GET_{PREV,NEXT} to retrieve information about the mount
namespace in one go.
(1) and (2) can be implemented for other namespace types easily.
Together with recent api additions this means one can iterate through
all mounts in all mount namespaces without ever touching procfs.
The commit message in 49224a345c48 ('Merge patch series "nsfs: iterate
through mount namespaces"') contains example code how to do this"
* tag 'vfs-6.12.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
nsfs: iterate through mount namespaces
file: add fput() cleanup helper
fs: add put_mnt_ns() cleanup helper
fs: allow mount namespace fd
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Make __fdget() et.al. return struct fd directly.
New helpers: BORROWED_FD(file) and CLONED_FD(file), for
borrowed and cloned file references resp.
NOTE: this might need tuning; in particular, inline on
__fget_light() is there to keep the code generation same as
before - we probably want to keep it inlined in fdget() et.al.
(especially so in fdget_pos()), but that needs profiling.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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We want the compiler to see that fdput() on empty instance
is a no-op. The emptiness check is that file reference is NULL,
while fdput() is "fput() if FDPUT_FPUT is present in flags".
The reason why fdput() on empty instance is a no-op is something
compiler can't see - it's that we never generate instances with
NULL file reference combined with non-zero flags.
It's not that hard to deal with - the real primitives behind
fdget() et.al. are returning an unsigned long value, unpacked by (inlined)
__to_fd() into the current struct file * + int. The lower bits are
used to store flags, while the rest encodes the pointer. Linus suggested
that keeping this unsigned long around with the extractions done by inlined
accessors should generate a sane code and that turns out to be the case.
Namely, turning struct fd into a struct-wrapped unsinged long, with
fd_empty(f) => unlikely(f.word == 0)
fd_file(f) => (struct file *)(f.word & ~3)
fdput(f) => if (f.word & 1) fput(fd_file(f))
ends up with compiler doing the right thing. The cost is the patch
footprint, of course - we need to switch f.file to fd_file(f) all over
the tree, and it's not doable with simple search and replace; there are
false positives, etc.
Note that the sole member of that structure is an opaque
unsigned long - all accesses should be done via wrappers and I don't
want to use a name that would invite manual casts to file pointers,
etc. The value of that member is equal either to (unsigned long)p | flags,
p being an address of some struct file instance, or to 0 for an empty fd.
For now the new predicate (fd_empty(f)) has no users; all the
existing checks have form (!fd_file(f)). We will convert to fd_empty()
use later; here we only define it (and tell the compiler that it's
unlikely to return true).
This commit only deals with representation change; there will
be followups.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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For any changes of struct fd representation we need to
turn existing accesses to fields into calls of wrappers.
Accesses to struct fd::flags are very few (3 in linux/file.h,
1 in net/socket.c, 3 in fs/overlayfs/file.c and 3 more in
explicit initializers).
Those can be dealt with in the commit converting to
new layout; accesses to struct fd::file are too many for that.
This commit converts (almost) all of f.file to
fd_file(f). It's not entirely mechanical ('file' is used as
a member name more than just in struct fd) and it does not
even attempt to distinguish the uses in pointer context from
those in boolean context; the latter will be eventually turned
into a separate helper (fd_empty()).
NOTE: mass conversion to fd_empty(), tempting as it
might be, is a bad idea; better do that piecewise in commit
that convert from fdget...() to CLASS(...).
[conflicts in fs/fhandle.c, kernel/bpf/syscall.c, mm/memcontrol.c
caught by git; fs/stat.c one got caught by git grep]
[fs/xattr.c conflict]
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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The explanatory comment above take_fd() contains a typo, fix that to not
confuse readers.
Signed-off-by: Mathias Krause <minipli@grsecurity.net>
Link: https://lore.kernel.org/r/20240809135035.748109-1-minipli@grsecurity.net
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Add a simple helper to put a file reference.
Link: https://lore.kernel.org/r/20240719-work-mount-namespace-v1-4-834113cab0d2@kernel.org
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Add a helper that returns the file descriptor and ensures that the old
variable contains a negative value. This makes it easy to rely on
CLASS(get_unused_fd).
Link: https://lore.kernel.org/r/20240627-work-pidfs-v1-1-7e9ab6cc3bb1@kernel.org
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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So we can also use CLASS(fd_raw, f)(fd) for codepaths where we allow
FMODE_PATH aka O_PATH file descriptors to be used.
Signed-off-by: Christian Brauner <brauner@kernel.org>
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When we open block devices as files we want to make sure to not charge
them against the open file limit of the caller as that can cause
spurious failures.
Link: https://lore.kernel.org/r/20240123-vfs-bdev-file-v2-1-adbd023e19cc@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Honestly, there's little value in having a helper with and without that
int __user *ufd argument. It's just messy and doesn't really give us
anything. Just expose receive_fd() with that argument and get rid of
that helper.
Link: https://lore.kernel.org/r/20231130-vfs-files-fixes-v1-5-e73ca6f4ea83@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Not every subsystem needs to have their own specialized helper.
Just us the __receive_fd() helper.
Link: https://lore.kernel.org/r/20231130-vfs-files-fixes-v1-4-e73ca6f4ea83@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Use __attribute__((__cleanup__(func))) to build:
- simple auto-release pointers using __free()
- 'classes' with constructor and destructor semantics for
scope-based resource management.
- lock guards based on the above classes.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230612093537.614161713%40infradead.org
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These two interface were added in 091141a42 commit,
but now there is no place to call them.
The only user of fput/fget_many() was removed in commit
62906e89e63b ("io_uring: remove file batch-get optimisation").
A user of get_file_rcu_many() were removed in commit
f073531070d2 ("init: add an init_dup helper").
And replace atomic_long_sub/add to atomic_long_dec/inc
can improve performance.
Here are the test results of unixbench:
Cmd: ./Run -c 64 context1
Without patch:
System Benchmarks Partial Index BASELINE RESULT INDEX
Pipe-based Context Switching 4000.0 2798407.0 6996.0
========
System Benchmarks Index Score (Partial Only) 6996.0
With patch:
System Benchmarks Partial Index BASELINE RESULT INDEX
Pipe-based Context Switching 4000.0 3486268.8 8715.7
========
System Benchmarks Index Score (Partial Only) 8715.7
Signed-off-by: Gou Hao <gouhao@uniontech.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Export receive_fd() so that some modules can use
it to pass file descriptor between processes without
missing any security stuffs.
Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20210831103634.33-4-xieyongji@bytedance.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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receive_fd_replace shares almost no code with the general case, so split
it out. Also remove the "Bump the sock usage counts" comment from
both copies, as that is now what __receive_sock actually does.
[AV: ... and make the only user of receive_fd_replace() choose between
it and receive_fd() according to what userland had passed to it in
flags]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Expand __receive_fd() with support for replace_fd() for the coming seccomp
"addfd" ioctl(). Add new wrapper receive_fd_replace() for the new behavior
and update existing wrappers to retain old behavior.
Thanks to Colin Ian King <colin.king@canonical.com> for pointing out an
uninitialized variable exposure in an earlier version of this patch.
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dmitry Kadashev <dkadashev@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Sargun Dhillon <sargun@sargun.me>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
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For both pidfd and seccomp, the __user pointer is not used. Update
__receive_fd() to make writing to ufd optional via a NULL check. However,
for the receive_fd_user() wrapper, ufd is NULL checked so an -EFAULT
can be returned to avoid changing the SCM_RIGHTS interface behavior. Add
new wrapper receive_fd() for pidfd and seccomp that does not use the ufd
argument. For the new helper, the allocated fd needs to be returned on
success. Update the existing callers to handle it.
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Sargun Dhillon <sargun@sargun.me>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
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In preparation for users of the "install a received file" logic outside
of net/ (pidfd and seccomp), relocate and rename __scm_install_fd() from
net/core/scm.c to __receive_fd() in fs/file.c, and provide a wrapper
named receive_fd_user(), as future patches will change the interface
to __receive_fd().
Additionally add a comment to fd_install() as a counterpoint to how
__receive_fd() interacts with fput().
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Dmitry Kadashev <dkadashev@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Sargun Dhillon <sargun@sargun.me>
Cc: Ido Schimmel <idosch@idosch.org>
Cc: Ioana Ciornei <ioana.ciornei@nxp.com>
Cc: linux-fsdevel@vger.kernel.org
Cc: netdev@vger.kernel.org
Reviewed-by: Sargun Dhillon <sargun@sargun.me>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
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Extern declarations in .c files are a bad style and can lead to
mismatches. Use existing definitions in headers where they exist,
and otherwise move the external declarations to suitable header
files.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Dmitry reports that a test case shows that io_uring isn't honoring a
modified rlimit nofile setting. get_unused_fd_flags() checks the task
signal->rlimi[] for the limits. As this isn't easily inheritable,
provide a __get_unused_fd_flags() that takes the value instead. Then we
can grab it when the request is prepared (from the original task), and
pass that in when we do the async part part of the open.
Reported-by: Dmitry Kadashev <dkadashev@gmail.com>
Tested-by: Dmitry Kadashev <dkadashev@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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This introduces a function which can be used to fetch a file, given an
arbitrary task. As long as the user holds a reference (refcnt) to the
task_struct it is safe to call, and will either return NULL on failure,
or a pointer to the file, with a refcnt.
This patch is based on Oleg Nesterov's (cf. [1]) patch from September
2018.
[1]: Link: https://lore.kernel.org/r/20180915160423.GA31461@redhat.com
Signed-off-by: Sargun Dhillon <sargun@sargun.me>
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20200107175927.4558-2-sargun@sargun.me
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
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Some uses cases repeatedly get and put references to the same file, but
the only exposed interface is doing these one at the time. As each of
these entail an atomic inc or dec on a shared structure, that cost can
add up.
Add fget_many(), which works just like fget(), except it takes an
argument for how many references to get on the file. Ditto fput_many(),
which can drop an arbitrary number of references to a file.
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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alloc_file_clone(old_file, mode, ops): create a new struct file with
->f_path equal to that of old_file. pipe converted.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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takes inode, vfsmount, name, O_... flags and file_operations and
either returns a new struct file (in which case inode reference we
held is consumed) or returns ERR_PTR(), in which case no refcounts
are altered.
converted aio_private_file() and sock_alloc_file() to it
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Just check FMODE_OPENED in __fput() and be done with that...
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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... so that it could set both ->f_flags and ->f_mode, without callers
having to set ->f_flags manually.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.
By default all files without license information are under the default
license of the kernel, which is GPL version 2.
Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.
How this work was done:
Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,
Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.
The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.
The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.
Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).
All documentation files were explicitly excluded.
The following heuristics were used to determine which SPDX license
identifiers to apply.
- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.
For non */uapi/* files that summary was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139
and resulted in the first patch in this series.
If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930
and resulted in the second patch in this series.
- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:
SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1
and that resulted in the third patch in this series.
- when the two scanners agreed on the detected license(s), that became
the concluded license(s).
- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.
- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).
- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.
- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.
In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.
Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.
Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.
In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.
Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct
This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.
These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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same as read() on regular files has, and for the same reason.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Macro get_unused_fd() is used to allocate a file descriptor with default
flags. Those default flags (0) don't enable close-on-exec.
This can be seen as an unsafe default: in most case close-on-exec should
be enabled to not leak file descriptor across exec().
It would be better to have a "safer" default set of flags, eg. O_CLOEXEC
must be used to enable close-on-exec.
Instead this patch removes get_unused_fd() so that out of tree modules
won't be affect by a runtime behavor change which might introduce other
kind of bugs: it's better to catch the change at build time, making it
easier to fix.
Removing the macro will also promote use of get_unused_fd_flags() (or
anon_inode_getfd()) with flags provided by userspace. Or, if flags cannot
be given by userspace, with flags set to O_CLOEXEC by default.
Signed-off-by: Yann Droneaud <ydroneaud@opteya.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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instead of returning the flags by reference, we can just have the
low-level primitive return those in lower bits of unsigned long,
with struct file * derived from the rest.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Our write() system call has always been atomic in the sense that you get
the expected thread-safe contiguous write, but we haven't actually
guaranteed that concurrent writes are serialized wrt f_pos accesses, so
threads (or processes) that share a file descriptor and use "write()"
concurrently would quite likely overwrite each others data.
This violates POSIX.1-2008/SUSv4 Section XSI 2.9.7 that says:
"2.9.7 Thread Interactions with Regular File Operations
All of the following functions shall be atomic with respect to each
other in the effects specified in POSIX.1-2008 when they operate on
regular files or symbolic links: [...]"
and one of the effects is the file position update.
This unprotected file position behavior is not new behavior, and nobody
has ever cared. Until now. Yongzhi Pan reported unexpected behavior to
Michael Kerrisk that was due to this.
This resolves the issue with a f_pos-specific lock that is taken by
read/write/lseek on file descriptors that may be shared across threads
or processes.
Reported-by: Yongzhi Pan <panyongzhi@gmail.com>
Reported-by: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-bs: Al Viro <viro@zeniv.linux.org.uk>
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no callers outside of fs/file.c left
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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analog of dup2(), except that it takes struct file * as source.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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... and get_unused_fd() a macro around it
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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... and schedule_work() for interrupt/kernel_thread callers
(and yes, now it *is* OK to call from interrupt).
We are guaranteed that __fput() will be done before we return
to userland (or exit). Note that for fput() from a kernel
thread we get an async behaviour; it's almost always OK, but
sometimes you might need to have __fput() completed before
you do anything else. There are two mechanisms for that -
a general barrier (flush_delayed_fput()) and explicit
__fput_sync(). Both should be used with care (as was the
case for fput() from kernel threads all along). See comments
in fs/file_table.c for details.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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New flag for open(2) - O_PATH. Semantics:
* pathname is resolved, but the file itself is _NOT_ opened
as far as filesystem is concerned.
* almost all operations on the resulting descriptors shall
fail with -EBADF. Exceptions are:
1) operations on descriptors themselves (i.e.
close(), dup(), dup2(), dup3(), fcntl(fd, F_DUPFD),
fcntl(fd, F_DUPFD_CLOEXEC, ...), fcntl(fd, F_GETFD),
fcntl(fd, F_SETFD, ...))
2) fcntl(fd, F_GETFL), for a common non-destructive way to
check if descriptor is open
3) "dfd" arguments of ...at(2) syscalls, i.e. the starting
points of pathname resolution
* closing such descriptor does *NOT* affect dnotify or
posix locks.
* permissions are checked as usual along the way to file;
no permission checks are applied to the file itself. Of course,
giving such thing to syscall will result in permission checks (at
the moment it means checking that starting point of ....at() is
a directory and caller has exec permissions on it).
fget() and fget_light() return NULL on such descriptors; use of
fget_raw() and fget_raw_light() is needed to get them. That protects
existing code from dealing with those things.
There are two things still missing (they come in the next commits):
one is handling of symlinks (right now we refuse to open them that
way; see the next commit for semantics related to those) and another
is descriptor passing via SCM_RIGHTS datagrams.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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In fput_light(), there's an unlikely(fput_needed), which running on
my normal desktop doing firefox, xchat, evolution and part of my distcc farm,
and running the annotate branch profiler shows that the unlikely is not
very unlikely.
correct incorrect % Function File Line
------- --------- - -------- ---- ----
0 48 100 fput_light file.h 26
115828710 897415279 88 fput_light file.h 26
865271179 5286128445 85 fput_light file.h 26
19568539 8923664 31 fput_light file.h 26
12353677 3562279 22 fput_light file.h 26
267691 67062 20 fput_light file.h 26
15014853 348172 2 fput_light file.h 26
209258 205 0 fput_light file.h 26
1364164 0 0 fput_light file.h 26
Which gives 1032903812 times it was correct and 6203351846 times it was
incorrect, or 85% incorrect.
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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__aio_put_req() plays sick games with file refcount. What
it wants is fput() from atomic context; it's almost always
done with f_count > 1, so they only have to deal with delayed
work in rare cases when their reference happens to be the
last one. Current code decrements f_count and if it hasn't
hit 0, everything is fine. Otherwise it keeps a pointer
to struct file (with zero f_count!) around and has delayed
work do __fput() on it.
Better way to do it: use atomic_long_add_unless( , -1, 1)
instead of !atomic_long_dec_and_test(). IOW, decrement it
only if it's not the last reference, leave refcount alone
if it was. And use normal fput() in delayed work.
I've made that atomic_long_add_unless call a new helper -
fput_atomic(). Drops a reference to file if it's safe to
do in atomic (i.e. if that's not the last one), tells if
it had been able to do that. aio.c converted to it, __fput()
use is gone. req->ki_file *always* contributes to refcount
now. And __fput() became static.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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... and have the caller grab both mnt and dentry; kill
leak in infiniband, while we are at it.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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New primitive: alloc_fd(start, flags). get_unused_fd() and
get_unused_fd_flags() become wrappers on top of it.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Initial splitoff of the low-level stuff; taken to fdtable.h
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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