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Miklos Szeredi points out that we need to also worry about memory
odering when doing the dentry name comparison asynchronously with RCU.
In particular, doing a rename can do a memcpy() of one dentry name over
another, and we want to make sure that any unlocked reader will always
see the proper terminating NUL character, so that it won't ever run off
the allocation.
Rather than having to be extra careful with the name copy or at lookup
time for each character, this resolves the issue by making sure that all
names that are inlined in the dentry always have a NUL character at the
end of the name allocation. If we do that at dentry allocation time, we
know that no future name copy will ever change that final NUL to
anything else, so there are no memory ordering issues.
So even if a concurrent rename ends up overwriting the NUL character
that terminates the original name, we always know that there is one
final NUL at the end, and there is no worry about the lockless RCU
lookup traversing the name too far.
The out-of-line allocations are never copied over, so we can just make
sure that we write the name (with terminating NULL) and do a write
barrier before we expose the name to anything else by setting it in the
dentry.
Reported-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Nick Piggin <npiggin@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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We had for some reason overlooked the AIO interface, and it didn't use
the proper rw_verify_area() helper function that checks (for example)
mandatory locking on the file, and that the size of the access doesn't
cause us to overflow the provided offset limits etc.
Instead, AIO did just the security_file_permission() thing (that
rw_verify_area() also does) directly.
This fixes it to do all the proper helper functions, which not only
means that now mandatory file locking works with AIO too, we can
actually remove lines of code.
Reported-by: Manish Honap <manish_honap_vit@yahoo.co.in>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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During early boot, when the scheduler hasn't really been fully set up,
we really can't do blocking allocations because with certain (dubious)
configurations the "might_resched()" calls can actually result in
scheduling events.
We could just make such users always use GFP_ATOMIC, but quite often the
code that does the allocation isn't really aware of the fact that the
scheduler isn't up yet, and forcing that kind of random knowledge on the
initialization code is just annoying and not good for anybody.
And we actually have a the 'gfp_allowed_mask' exactly for this reason:
it's just that the kernel init sequence happens to set it to allow
blocking allocations much too early.
So move the 'gfp_allowed_mask' initialization from 'start_kernel()'
(which is some of the earliest init code, and runs with preemption
disabled for good reasons) into 'kernel_init()'. kernel_init() is run
in the newly created thread that will become the 'init' process, as
opposed to the early startup code that runs within the context of what
will be the first idle thread.
So by the time we reach 'kernel_init()', we know that the scheduler must
be at least limping along, because we've already scheduled from the idle
thread into the init thread.
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Cc: David Rientjes <rientjes@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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There is no point having the NET dependency on the select target, as it
forces all users to depend on NET to tell they support BPF_JIT. Move
the config option to the bottom of the file - this could be a nice place
also for future "selectable" config symbols.
Fix up all users to drop the dependency on NET now that it is not
required to supress warnings for non-NET builds.
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: David Miller <davem@davemloft.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Signed-off-by: Vipul Pandya <vipul@chelsio.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
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Use single_release() instead of seq_release() to free memory allocated
by single_open().
Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Signed-off-by: Steven Miao <realmz6@gmail.com>
Signed-off-by: Bob Liu <lliubbo@gmail.com>
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Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Bob Liu <lliubbo@gmail.com>
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Linus Torvalds
Sam Ravnborg
Vipul Pandya
Djalal Harouni
Steven Miao
Sonic Zhang