Use getattr to get an accurate link count when needed. This is cheaper and
more accurate than trying to derive it by walking the thread list of a
process.
Especially as it happens when needed stat instead of at readdir time.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Long ago and far away in 2.2 we started checking to ensure the files we
displayed in /proc were visible to the current process. It was an
unsophisticated time and no one was worried about functions full of FIXMES in
a stable kernel. As time passed the function became sacred and was enshrined
in the shrine of how things have always been. The fixes came in but only to
keep the function working no one really remembering or documenting why we did
things that way.
The intent and the functionality make a lot of sense. Don't let /proc be an
access point for files a process can see no other way. The implementation
however is completely wrong.
We are currently checking the root directories of the two processes, we are
not checking the actual file descriptors themselves.
We are strangely checking with a permission method instead of just when we use
the data.
This patch fixes the logic to actually check the file descriptors and make a
note that implementing a permission method for this part of /proc almost
certainly indicates a bug in the reasoning.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The inode operations only exist to support the proc_permission function.
Currently mem_read and mem_write have all the same permission checks as
ptrace. The fs check makes no sense in this context, and we can trivially get
around it by calling ptrace.
So simply the code by killing the strange weird case.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
First we can access every /proc/<tgid>/task/<pid> directory as /proc/<pid> so
proc_task_permission is not usefully limiting visibility.
Second having related filesystems information should have nothing to do with
process visibility. kill does not implement any checks like that.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The sole renaming use of proc_inode.type is to discover the file descriptor
number, so just store the file descriptor number and don't wory about
processing this field. This removes any /proc limits on the maximum number of
file descriptors, and clears the path to make the hard coded /proc inode
numbers go away.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Currently in /proc if the task is dumpable all of files are owned by the tasks
effective users. Otherwise the files are owned by root. Unless it is the
/proc/<tgid>/ or /proc/<tgid>/task/<pid> directory in that case we always make
the directory owned by the effective user.
However the special case for directories is pointless except as a way to read
the effective user, because the permissions on both of those directories are
world readable, and executable.
/proc/<tgid>/status provides a much better way to read a processes effecitve
userid, so it is silly to try to provide that on the directory.
So this patch simplifies the code by removing a pointless special case and
gets us one step closer to being able to remove the hard coded /proc inode
numbers.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The removed fields are already set by proc_alloc_inode. Initializing them in
proc_alloc_inode implies they need it for proper cleanup. At least ei->pde
was not set on all paths making it look like proc_alloc_inode was buggy. So
just remove the redundant assignments.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
We already call everything except do_proc_readlink outside of the BKL in
proc_pid_followlink, and there appears to be nothing in do_proc_readlink that
needs any special protection.
So remove this leftover from one of the BKL cleanup efforts.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
I noticed recently that my CONFIG_CRYPTO_MD5 turned into a y again instead
of m. It turns out that CONFIG_NFSD_V4 is selecting it to be y even though
I've chosen to compile nfsd as a module.
In general when we have a bool sitting under a tristate it is better to
select things you need from the tristate rather than the bool since that
allows the things you select to be modules.
The following patch does it for nfsd.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Add the IOCTLs of the Gigaset drivers to compat_ioctl.h in order to make
them available for 32 bit programs on 64 bit platforms. Please merge.
Signed-off-by: Hansjoerg Lipp <hjlipp@web.de>
Acked-by: Tilman Schmidt <tilman@imap.cc>
Cc: Karsten Keil <kkeil@suse.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch adds "-o bh" option to force use of buffer_heads. This option
is needed when we make "nobh" as default - and if we run into problems.
Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Add a /proc/<pid>/attr/keycreate entry that stores the appropriate context for
newly-created keys. Modify the selinux_key_alloc hook to make use of the new
entry. Update the flask headers to include a new "setkeycreate" permission
for processes. Update the flask headers to include a new "create" permission
for keys. Use the create permission to restrict which SIDs each task can
assign to newly-created keys. Add a new parameter to the security hook
"security_key_alloc" to indicate whether it is being invoked by the kernel, or
from userspace. If it is being invoked by the kernel, the security hook
should never fail. Update the documentation to reflect these changes.
Signed-off-by: Michael LeMay <mdlemay@epoch.ncsc.mil>
Signed-off-by: James Morris <jmorris@namei.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch converts the combination of list_del(A) and list_add(A, B) to
list_move(A, B) under fs/.
Cc: Ian Kent <raven@themaw.net>
Acked-by: Joel Becker <joel.becker@oracle.com>
Cc: Neil Brown <neilb@cse.unsw.edu.au>
Cc: Hans Reiser <reiserfs-dev@namesys.com>
Cc: Urban Widmark <urban@teststation.com>
Acked-by: David Howells <dhowells@redhat.com>
Acked-by: Mark Fasheh <mark.fasheh@oracle.com>
Signed-off-by: Akinobu Mita <mita@miraclelinux.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch converts the combination of list_del(A) and list_add(A, B) to
list_move(A, B).
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Akinobu Mita <mita@miraclelinux.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch converts list_add(A, B.prev) to list_add_tail(A, &B) for
readability.
Acked-by: Karsten Keil <kkeil@suse.de>
Cc: Jan Harkes <jaharkes@cs.cmu.edu>
Acked-by: Jan Kara <jack@suse.cz>
AOLed-by: David Woodhouse <dwmw2@infradead.org>
Cc: Sridhar Samudrala <sri@us.ibm.com>
Signed-off-by: Akinobu Mita <mita@miraclelinux.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
CIFS takes/releases f_owner.lock - why? It does not change anything in the
fowner state. Remove this locking.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Steve French <sfrench@us.ibm.com>
We lose property writing functionality for the time being, but
that will be easy to add back. The code and framework is so
much simpler now.
Signed-off-by: David S. Miller <davem@davemloft.net>
binfmt_flat.c calls set_personality with PER_LINUX as the personality.
On the arm architecture this results in the program running in 26bit
usermode. PER_LINUX_32BIT should be used instead. This doesn't affect
other architectures that use binfmt_flat.
Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Trond had apparently merged the same patch twice, causing a duplicate
include of the "internal.h" file, with resulting obvious confusion.
Tssk. I'm the only one allowed to send out trees that don't even
compile! Who does this Trond guy think he is?
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
likely profiling shows that the following is a miss.
After boot:
[+- ] Type | # True | # False | Function:Filename@Line
+unlikely | 1074| 0 prune_dcache()@:fs/dcache.c@409
After a bonnie++ run:
+unlikely | 66716| 19584 prune_dcache()@:fs/dcache.c@409
So remove it.
Signed-off-by: Hua Zhong <hzhong@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Things which force me think a little: why so?
Signed-off-by: Evgeniy Dushistov <dushistov@mail.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
When the linkat() syscall was added the flag parameter was added in the
last minute but it wasn't used so far. The following patch should change
that. My tests show that this is all that's needed.
If OLDNAME is a symlink setting the flag causes linkat to follow the
symlink and create a hardlink with the target. This is actually the
behavior POSIX demands for link() as well but Linux wisely does not do
this. With this flag (which will most likely be in the next POSIX
revision) the programmer can choose the behavior, defaulting to the safe
variant. As a side effect it is now possible to implement a
POSIX-compliant link(2) function for those who are interested.
touch file
ln -s file symlink
linkat(fd, "symlink", fd, "newlink", 0)
-> newlink is hardlink of symlink
linkat(fd, "symlink", fd, "newlink", AT_SYMLINK_FOLLOW)
-> newlink is hardlink of file
The value of AT_SYMLINK_FOLLOW is determined by the definition we already
use in glibc.
Signed-off-by: Ulrich Drepper <drepper@redhat.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
If you do a poll() call with timeout -1, the wait will be a big number
(depending on HZ) instead of infinite wait, since -1 is passed to the
msecs_to_jiffies function.
Signed-off-by: Frode Isaksen <frode.isaksen@gmail.com>
Acked-by: Nishanth Aravamudan <nacc@us.ibm.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
%s is only valid if array is known to contain NUL or precision is given and
does not exceed the size of array.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Update smbiod to use kthread instead of deprecated kernel_thread.
[akpm@osdl.org: cleanup]
Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
coverity found two needless checks in vfs_inode.c (cid #1165 and #1164)
In both cases inode is always NULL when we goto error; either because it
is still initialized to NULL or is set to NULL explicitly. This patch
simply removes these checks to save some code.
Signed-off-by: Eric Sesterhenn <snakebyte@gmx.de>
Acked-by: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Ron Minnich <rminnich@lanl.gov>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
VFS uses current->files pointer as lock owner ID, and it wouldn't be
prudent to expose this value to userspace. So scramble it with XTEA using
a per connection random key, known only to the kernel. Only one direction
needs to be implemented, since the ID is never sent in the reverse
direction.
The XTEA algorithm is implemented inline since it's simple enough to do so,
and this adds less complexity than if the crypto API were used.
Thanks to Jesper Juhl for the idea.
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Add synchronous request interruption. This is needed for file locking
operations which have to be interruptible. However filesystem may implement
interruptibility of other operations (e.g. like NFS 'intr' mount option).
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Rename the 'interrupted' flag to 'aborted', since it indicates exactly that,
and next patch will introduce an 'interrupted' flag for a
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
All POSIX locks owned by the current task are removed on close(). If the
FLUSH request resulting initiated by close() fails to reach userspace, there
might be locks remaining, which cannot be removed.
The only reason it could fail, is if allocating the request fails. In this
case use the request reserved for RELEASE, or if that is currently used by
another FLUSH, wait for it to become available.
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch adds POSIX file locking support to the fuse interface.
This implementation doesn't keep any locking state in kernel. Unlocking on
close() is handled by the FLUSH message, which now contains the lock owner id.
Mandatory locking is not supported. The filesystem may enfoce mandatory
locking in userspace if needed.
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Add a control filesystem to fuse, replacing the attributes currently exported
through sysfs. An empty directory '/sys/fs/fuse/connections' is still created
in sysfs, and mounting the control filesystem here provides backward
compatibility.
Advantages of the control filesystem over the previous solution:
- allows the object directory and the attributes to be owned by the
filesystem owner, hence letting unpriviled users abort the
filesystem connection
- does not suffer from module unload race
[akpm@osdl.org: fix this fs for recent dhowells depredations]
[akpm@osdl.org: fix 64-bit printk warnings]
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Don't put requests into the background when a fatal interrupt occurs while the
request is in userspace. This removes a major wart from the implementation.
Backgrounding of requests was introduced to allow breaking of deadlocks.
However now the same can be achieved by aborting the filesystem through the
'abort' sysfs attribute.
This is a change in the interface, but should not cause problems, since these
kinds of deadlocks never happen during normal operation.
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
I've found a case where invalid dentrys in a mount tree, waiting to be
cleaned up by d_invalidate, prevent the expected expire.
In this case dentrys created during a lookup for which a mount fails or has
no entry in the mount map contribute to the d_count of the parent dentry.
These dentrys may not be invalidated prior to comparing the interanl usage
count of valid autofs dentrys against the dentry d_count which makes a
mount tree appear busy so it doesn't expire.
Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
In the course of trying to track down a bug where a file mtime was not
being updated correctly, it was discovered that the m/ctime updates were
not quite being handled correctly for ftruncate() calls.
Quoth SUSv3:
open(2):
If O_TRUNC is set and the file did previously exist, upon
successful completion, open() shall mark for update the st_ctime
and st_mtime fields of the file.
truncate(2):
Upon successful completion, if the file size is changed, this
function shall mark for update the st_ctime and st_mtime fields
of the file, and the S_ISUID and S_ISGID bits of the file mode
may be cleared.
ftruncate(2):
Upon successful completion, if fildes refers to a regular file,
the ftruncate() function shall mark for update the st_ctime and
st_mtime fields of the file and the S_ISUID and S_ISGID bits of
the file mode may be cleared. If the ftruncate() function is
unsuccessful, the file is unaffected.
The open(O_TRUNC) and truncate cases were being handled correctly, but the
ftruncate case was being handled like the truncate case. The semantics of
truncate and ftruncate don't quite match, so ftruncate needs to be handled
slightly differently.
The attached patch addresses this issue for ftruncate(2).
My thanx to Stephen Tweedie and Trond Myklebust for their help in
understanding the situation and semantics.
Signed-off-by: Peter Staubach <staubach@redhat.com>
Cc: "Stephen C. Tweedie" <sct@redhat.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The variables nlen and rlen are defined/initialized but not used in
ext3_add_entry().
Signed-off-by: Johann Lombardi <johann.lombardi@bull.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
A few days ago Arjan signaled a lockdep red flag on epoll locks, and
precisely between the epoll's device structure lock (->lock) and the wait
queue head lock (->lock).
Like I explained in another email, and directly to Arjan, this can't happen
in reality because of the explicit check at eventpoll.c:592, that does not
allow to drop an epoll fd inside the same epoll fd. Since lockdep is
working on per-structure locks, it will never be able to know of policies
enforced in other parts of the code.
It was decided time ago of having the ability to drop epoll fds inside
other epoll fds, that triggers a very trick wakeup operations (due to
possibly reentrant callback-driven wakeups) handled by the
ep_poll_safewake() function. While looking again at the code though, I
noticed that all the operations done on the epoll's main structure wait
queue head (->wq) are already protected by the epoll lock (->lock), so that
locked-style functions can be used to manipulate the ->wq member. This
makes both a lock-acquire save, and lockdep happy.
Running totalmess on my dual opteron for a while did not reveal any problem
so far:
http://www.xmailserver.org/totalmess.c
Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch makes EXT2_DEBUG work again. Due to lack of proper include
file, EXT2_DEBUG was undefined in bitmap.c and ext2_count_free() is left
out. Moved to balloc.c and removed bitmap.c entirely.
Second, debug versions of ext2_count_free_{inodes/blocks} reacquires
superblock lock. Moved lock into callers.
Signed-off-by: Val Henson <val_henson@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Make procfs non-optional unless EMBEDDED is set, just like sysfs. procfs
is already de facto required for a large subset of Linux functionality.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Convert the ext3 in-kernel filesystem blocks to ext3_fsblk_t. Convert the
rest of all unsigned long type in-kernel filesystem blocks to ext3_fsblk_t,
and replace the printk format string respondingly.
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Some of the in-kernel ext3 block variable type are treated as signed 4 bytes
int type, thus limited ext3 filesystem to 8TB (4kblock size based). While
trying to fix them, it seems quite confusing in the ext3 code where some
blocks are filesystem-wide blocks, some are group relative offsets that need
to be signed value (as -1 has special meaning). So it seem saner to define
two types of physical blocks: one is filesystem wide blocks, another is
group-relative blocks. The following patches clarify these two types of
blocks in the ext3 code, and fix the type bugs which limit current 32 bit ext3
filesystem limit to 8TB.
With this series of patches and the percpu counter data type changes in the mm
tree, we are able to extend exts filesystem limit to 16TB.
This work is also a pre-request for the recent >32 bit ext3 work, and makes
the kernel to able to address 48 bit ext3 block a lot easier: Simply redefine
ext3_fsblk_t from unsigned long to sector_t and redefine the format string for
ext3 filesystem block corresponding.
Two RFC with a series patches have been posted to ext2-devel list and have
been reviewed and discussed:
http://marc.theaimsgroup.com/?l=ext2-devel&m=114722190816690&w=2http://marc.theaimsgroup.com/?l=ext2-devel&m=114784919525942&w=2
Patches are tested on both 32 bit machine and 64 bit machine, <8TB ext3 and
>8TB ext3 filesystem(with the latest to be released e2fsprogs-1.39). Tests
includes overnight fsx, tiobench, dbench and fsstress.
This patch:
Defines ext3_fsblk_t and ext3_grpblk_t, and the printk format string for
filesystem wide blocks.
This patch classifies all block group relative blocks, and ext3_fsblk_t blocks
occurs in the same function where used to be confusing before. Also include
kernel bug fixes for filesystem wide in-kernel block variables. There are
some fileystem wide blocks are treated as int/unsigned int type in the kernel
currently, especially in ext3 block allocation and reservation code. This
patch fixed those bugs by converting those variables to ext3_fsblk_t(unsigned
long) type.
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The problem is that when we write to a file, the copy from userspace to
pagecache is first done with preemption disabled, so if the source address is
not immediately available the copy fails *and* *zeros* *the* *destination*.
This is a problem because a concurrent read (which admittedly is an odd thing
to do) might see zeros rather that was there before the write, or what was
there after, or some mixture of the two (any of these being a reasonable thing
to see).
If the copy did fail, it will immediately be retried with preemption
re-enabled so any transient problem with accessing the source won't cause an
error.
The first copying does not need to zero any uncopied bytes, and doing so
causes the problem. It uses copy_from_user_atomic rather than copy_from_user
so the simple expedient is to change copy_from_user_atomic to *not* zero out
bytes on failure.
The first of these two patches prepares for the change by fixing two places
which assume copy_from_user_atomic does zero the tail. The two usages are
very similar pieces of code which copy from a userspace iovec into one or more
page-cache pages. These are changed to remove the assumption.
The second patch changes __copy_from_user_inatomic* to not zero the tail.
Once these are accepted, I will look at similar patches of other architectures
where this is important (ppc, mips and sparc being the ones I can find).
This patch:
There is a problem with __copy_from_user_inatomic zeroing the tail of the
buffer in the case of an error. As it is called in atomic context, the error
may be transient, so it results in zeros being written where maybe they
shouldn't be.
In the usage in filemap, this opens a window for a well timed read to see data
(zeros) which is not consistent with any ordering of reads and writes.
Most cases where __copy_from_user_inatomic is called, a failure results in
__copy_from_user being called immediately. As long as the latter zeros the
tail, the former doesn't need to. However in *copy_from_user_iovec
implementations (in both filemap and ntfs/file), it is assumed that
copy_from_user_inatomic will zero the tail.
This patch removes that assumption, so that after this patch it will
be safe for copy_from_user_inatomic to not zero the tail.
This patch also adds some commentary to filemap.h and asm-i386/uaccess.h.
After this patch, all architectures that might disable preempt when
kmap_atomic is called need to have their __copy_from_user_inatomic* "fixed".
This includes
- powerpc
- i386
- mips
- sparc
Signed-off-by: Neil Brown <neilb@suse.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Anton Altaparmakov <aia21@cantab.net>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: William Lee Irwin III <wli@holomorphy.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This was reported as Debian bug #336604.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Eric W. Biederman