linux/kernel/futex_compat.c, branch v2.6.27.59

futex_compat __user annotation

2008-03-30T21:18:41Z

Signed-off-by: Al Viro Signed-off-by: Linus Torvalds

futex: runtime enable pi and robust functionality

2008-02-24T01:12:15Z

Not all architectures implement futex_atomic_cmpxchg_inatomic(). The default implementation returns -ENOSYS, which is currently not handled inside of the futex guts. Futex PI calls and robust list exits with a held futex result in an endless loop in the futex code on architectures which have no support. Fixing up every place where futex_atomic_cmpxchg_inatomic() is called would add a fair amount of extra if/else constructs to the already complex code. It is also not possible to disable the robust feature before user space tries to register robust lists. Compile time disabling is not a good idea either, as there are already architectures with runtime detection of futex_atomic_cmpxchg_inatomic support. Detect the functionality at runtime instead by calling cmpxchg_futex_value_locked() with a NULL pointer from the futex initialization code. This is guaranteed to fail, but the call of futex_atomic_cmpxchg_inatomic() happens with pagefaults disabled. On architectures, which use the asm-generic implementation or have a runtime CPU feature detection, a -ENOSYS return value disables the PI/robust features. On architectures with a working implementation the call returns -EFAULT and the PI/robust features are enabled. The relevant syscalls return -ENOSYS and the robust list exit code is blocked, when the detection fails. Fixes http://lkml.org/lkml/2008/2/11/149 Originally reported by: Lennart Buytenhek Signed-off-by: Thomas Gleixner Acked-by: Ingo Molnar Cc: Lennert Buytenhek Cc: Riku Voipio Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

hrtimer: check relative timeouts for overflow

2008-02-14T21:08:30Z

Various user space callers ask for relative timeouts. While we fixed that overflow issue in hrtimer_start(), the sites which convert relative user space values to absolute timeouts themself were uncovered. Instead of putting overflow checks into each place add a function which does the sanity checking and convert all affected callers to use it. Thanks to Frans Pop, who reported the problem and tested the fixes. Signed-off-by: Thomas Gleixner Acked-by: Ingo Molnar Tested-by: Frans Pop

futex: Add bitset conditional wait/wakeup functionality

2008-02-01T16:45:14Z

To allow the implementation of optimized rw-locks in user space, glibc needs a possibility to select waiters for wakeup depending on a bitset mask. This requires two new futex OPs: FUTEX_WAIT_BITS and FUTEX_WAKE_BITS These OPs are basically the same as FUTEX_WAIT and FUTEX_WAKE plus an additional argument - a bitset. Further the FUTEX_WAIT_BITS OP is expecting an absolute timeout value instead of the relative one, which is used for the FUTEX_WAIT OP. FUTEX_WAIT_BITS calls into the kernel with a bitset. The bitset is stored in the futex_q structure, which is used to enqueue the waiter into the hashed futex waitqueue. FUTEX_WAKE_BITS also calls into the kernel with a bitset. The wakeup function logically ANDs the bitset with the bitset stored in each waiters futex_q structure. If the result is zero (i.e. none of the set bits in the bitsets is matching), then the waiter is not woken up. If the result is not zero (i.e. one of the set bits in the bitsets is matching), then the waiter is woken. The bitset provided by the caller must be non zero. In case the provided bitset is zero the kernel returns EINVAL. Internaly the new OPs are only extensions to the existing FUTEX_WAIT and FUTEX_WAKE functions. The existing OPs hand a bitset with all bits set into the futex_wait() and futex_wake() functions. Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar

[FUTEX] Fix address computation in compat code.

2007-11-10T00:13:08Z

compat_exit_robust_list() computes a pointer to the futex entry in userspace as follows: (void __user *)entry + futex_offset 'entry' is a 'struct robust_list __user *', and 'futex_offset' is a 'compat_long_t' (typically a 's32'). Things explode if the 32-bit sign bit is set in futex_offset. Type promotion sign extends futex_offset to a 64-bit value before adding it to 'entry'. This triggered a problem on sparc64 running 32-bit applications which would lock up a cpu looping forever in the fault handling for the userspace load in handle_futex_death(). Compat userspace runs with address masking (wherein the cpu zeros out the top 32-bits of every effective address given to a memory operation instruction) so the sparc64 fault handler accounts for this by zero'ing out the top 32-bits of the fault address too. Since the kernel properly uses the compat_uptr interfaces, kernel side accesses to compat userspace work too since they will only use addresses with the top 32-bit clear. Because of this compat futex layer bug we get into the following loop when executing the get_user() load near the top of handle_futex_death(): 1) load from address '0xfffffffff7f16bd8', FAULT 2) fault handler clears upper 32-bits, processes fault for address '0xf7f16bd8' which succeeds 3) goto #1 I want to thank Bernd Zeimetz, Josip Rodin, and Fabio Massimo Di Nitto for their tireless efforts helping me track down this bug. Signed-off-by: David S. Miller Signed-off-by: Linus Torvalds

Uninline find_task_by_xxx set of functions

2007-10-19T18:53:40Z

The find_task_by_something is a set of macros are used to find task by pid depending on what kind of pid is proposed - global or virtual one. All of them are wrappers above the most generic one - find_task_by_pid_type_ns() - and just substitute some args for it. It turned out, that dereferencing the current->nsproxy->pid_ns construction and pushing one more argument on the stack inline cause kernel text size to grow. This patch moves all this stuff out-of-line into kernel/pid.c. Together with the next patch it saves a bit less than 400 bytes from the .text section. Signed-off-by: Pavel Emelyanov Cc: Sukadev Bhattiprolu Cc: Oleg Nesterov Cc: Paul Menage Cc: "Eric W. Biederman" Acked-by: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

pid namespaces: changes to show virtual ids to user

2007-10-19T18:53:40Z

This is the largest patch in the set. Make all (I hope) the places where the pid is shown to or get from user operate on the virtual pids. The idea is: - all in-kernel data structures must store either struct pid itself or the pid's global nr, obtained with pid_nr() call; - when seeking the task from kernel code with the stored id one should use find_task_by_pid() call that works with global pids; - when showing pid's numerical value to the user the virtual one should be used, but however when one shows task's pid outside this task's namespace the global one is to be used; - when getting the pid from userspace one need to consider this as the virtual one and use appropriate task/pid-searching functions. [akpm@linux-foundation.org: build fix] [akpm@linux-foundation.org: nuther build fix] [akpm@linux-foundation.org: yet nuther build fix] [akpm@linux-foundation.org: remove unneeded casts] Signed-off-by: Pavel Emelyanov Signed-off-by: Alexey Dobriyan Cc: Sukadev Bhattiprolu Cc: Oleg Nesterov Cc: Paul Menage Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

robust futex thread exit race

2007-10-01T14:52:23Z

Calling handle_futex_death in exit_robust_list for the different robust mutexes of a thread basically frees the mutex. Another thread might grab the lock immediately which updates the next pointer of the mutex. fetch_robust_entry over the next pointer might therefore branch into the robust mutex list of a different thread. This can cause two problems: 1) some mutexes held by the dead thread are not getting freed and 2) some mutexs held by a different thread are freed. The next point need to be read before calling handle_futex_death. Signed-off-by: Martin Schwidefsky Acked-by: Ingo Molnar Acked-by: Thomas Gleixner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

futex_compat: fix list traversal bugs

2007-09-12T00:21:20Z

The futex list traversal on the compat side appears to have a bug. It's loop termination condition compares: while (compat_ptr(uentry) != &head->list) But that can't be right because "uentry" has the special "pi" indicator bit still potentially set at bit 0. This is cleared by fetch_robust_entry() into the "entry" return value. What this seems to mean is that the list won't terminate when list iteration gets back to the the head. And we'll also process the list head like a normal entry, which could cause all kinds of problems. So we should check for equality with "entry". That pointer is of the non-compat type so we have to do a little casting to keep the compiler and sparse happy. The same problem can in theory occur with the 'pending' variable, although that has not been reported from users so far. Based on the original patch from David Miller. Acked-by: Ingo Molnar Cc: Thomas Gleixner Cc: David Miller Signed-off-by: Arnd Bergmann Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Revert "futex_requeue_pi optimization"

2007-06-18T16:48:41Z

This reverts commit d0aa7a70bf03b9de9e995ab272293be1f7937822. It not only introduced user space visible changes to the futex syscall, it is also non-functional and there is no way to fix it proper before the 2.6.22 release. The breakage report ( http://lkml.org/lkml/2007/5/12/17 ) went unanswered, and unfortunately it turned out that the concept is not feasible at all. It violates the rtmutex semantics badly by introducing a virtual owner, which hacks around the coupling of the user-space pi_futex and the kernel internal rt_mutex representation. At the moment the only safe option is to remove it fully as it contains user-space visible changes to broken kernel code, which we do not want to expose in the 2.6.22 release. The patch reverts the original patch mostly 1:1, but contains a couple of trivial manual cleanups which were necessary due to patches, which touched the same area of code later. Verified against the glibc tests and my own PI futex tests. Signed-off-by: Thomas Gleixner Acked-by: Ingo Molnar Acked-by: Ulrich Drepper Cc: Pierre Peiffer Signed-off-by: Linus Torvalds