user/sven/linux.git/kernel/ptrace.c, branch leds/master

ptrace: ptrace_detach() can no longer race with SIGKILL

2015-04-17T13:04:06Z

ptrace_detach() re-checks ->ptrace under tasklist lock and calls release_task() if __ptrace_detach() returns true. This was needed because the __TASK_TRACED tracee could be killed/untraced, and it could even pass exit_notify() before we take tasklist_lock. But this is no longer possible after 9899d11f6544 "ptrace: ensure arch_ptrace/ptrace_request can never race with SIGKILL". We can turn these checks into WARN_ON() and remove release_task(). While at it, document the setting of child->exit_code. Signed-off-by: Oleg Nesterov Cc: Pavel Labath Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ptrace: fix race between ptrace_resume() and wait_task_stopped()

2015-04-17T13:04:06Z

ptrace_resume() is called when the tracee is still __TASK_TRACED. We set tracee->exit_code and then wake_up_state() changes tracee->state. If the tracer's sub-thread does wait() in between, task_stopped_code(ptrace => T) wrongly looks like another report from tracee. This confuses debugger, and since wait_task_stopped() clears ->exit_code the tracee can miss a signal. Test-case: #include #include #include #include #include #include int pid; void *waiter(void *arg) { int stat; for (;;) { assert(pid == wait(&stat)); assert(WIFSTOPPED(stat)); if (WSTOPSIG(stat) == SIGHUP) continue; assert(WSTOPSIG(stat) == SIGCONT); printf("ERR! extra/wrong report:%x\n", stat); } } int main(void) { pthread_t thread; pid = fork(); if (!pid) { assert(ptrace(PTRACE_TRACEME, 0,0,0) == 0); for (;;) kill(getpid(), SIGHUP); } assert(pthread_create(&thread, NULL, waiter, NULL) == 0); for (;;) ptrace(PTRACE_CONT, pid, 0, SIGCONT); return 0; } Note for stable: the bug is very old, but without 9899d11f6544 "ptrace: ensure arch_ptrace/ptrace_request can never race with SIGKILL" the fix should use lock_task_sighand(child). Signed-off-by: Oleg Nesterov Reported-by: Pavel Labath Tested-by: Pavel Labath Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ptrace: remove linux/compat.h inclusion under CONFIG_COMPAT

2015-02-17T22:34:51Z

Commit 84c751bd4aeb ("ptrace: add ability to retrieve signals without removing from a queue (v4)") includes globally in ptrace.c This patch removes inclusion under if defined CONFIG_COMPAT. Signed-off-by: Fabian Frederick Acked-by: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

exit: ptrace: shift "reap dead" code from exit_ptrace() to forget_original_parent()

2014-12-11T01:41:10Z

Now that forget_original_parent() uses ->ptrace_entry for EXIT_DEAD tasks, we can simply pass "dead_children" list to exit_ptrace() and remove another release_task() loop. Plus this way we do not need to drop and reacquire tasklist_lock. Also shift the list_empty(ptraced) check, if we want this optimization it makes sense to eliminate the function call altogether. Signed-off-by: Oleg Nesterov Cc: Aaron Tomlin Cc: Alexey Dobriyan Cc: "Eric W. Biederman" , Cc: Sterling Alexander Cc: Peter Zijlstra Cc: Roland McGrath Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

sched: Remove proliferation of wait_on_bit() action functions

2014-07-16T13:10:39Z

The current "wait_on_bit" interface requires an 'action' function to be provided which does the actual waiting. There are over 20 such functions, many of them identical. Most cases can be satisfied by one of just two functions, one which uses io_schedule() and one which just uses schedule(). So: Rename wait_on_bit and wait_on_bit_lock to wait_on_bit_action and wait_on_bit_lock_action to make it explicit that they need an action function. Introduce new wait_on_bit{,_lock} and wait_on_bit{,_lock}_io which are *not* given an action function but implicitly use a standard one. The decision to error-out if a signal is pending is now made based on the 'mode' argument rather than being encoded in the action function. All instances of the old wait_on_bit and wait_on_bit_lock which can use the new version have been changed accordingly and their action functions have been discarded. wait_on_bit{_lock} does not return any specific error code in the event of a signal so the caller must check for non-zero and interpolate their own error code as appropriate. The wait_on_bit() call in __fscache_wait_on_invalidate() was ambiguous as it specified TASK_UNINTERRUPTIBLE but used fscache_wait_bit_interruptible as an action function. David Howells confirms this should be uniformly "uninterruptible" The main remaining user of wait_on_bit{,_lock}_action is NFS which needs to use a freezer-aware schedule() call. A comment in fs/gfs2/glock.c notes that having multiple 'action' functions is useful as they display differently in the 'wchan' field of 'ps'. (and /proc/$PID/wchan). As the new bit_wait{,_io} functions are tagged "__sched", they will not show up at all, but something higher in the stack. So the distinction will still be visible, only with different function names (gds2_glock_wait versus gfs2_glock_dq_wait in the gfs2/glock.c case). Since first version of this patch (against 3.15) two new action functions appeared, on in NFS and one in CIFS. CIFS also now uses an action function that makes the same freezer aware schedule call as NFS. Signed-off-by: NeilBrown Acked-by: David Howells (fscache, keys) Acked-by: Steven Whitehouse (gfs2) Acked-by: Peter Zijlstra Cc: Oleg Nesterov Cc: Steve French Cc: Linus Torvalds Link: http://lkml.kernel.org/r/20140707051603.28027.72349.stgit@notabene.brown Signed-off-by: Ingo Molnar

kernel/compat: convert to COMPAT_SYSCALL_DEFINE

2014-03-06T14:35:10Z

Convert all compat system call functions where all parameter types have a size of four or less than four bytes, or are pointer types to COMPAT_SYSCALL_DEFINE. The implicit casts within COMPAT_SYSCALL_DEFINE will perform proper zero and sign extension to 64 bit of all parameters if needed. Signed-off-by: Heiko Carstens

exec/ptrace: fix get_dumpable() incorrect tests

2013-11-13T03:09:33Z

The get_dumpable() return value is not boolean. Most users of the function actually want to be testing for non-SUID_DUMP_USER(1) rather than SUID_DUMP_DISABLE(0). The SUID_DUMP_ROOT(2) is also considered a protected state. Almost all places did this correctly, excepting the two places fixed in this patch. Wrong logic: if (dumpable == SUID_DUMP_DISABLE) { /* be protective */ } or if (dumpable == 0) { /* be protective */ } or if (!dumpable) { /* be protective */ } Correct logic: if (dumpable != SUID_DUMP_USER) { /* be protective */ } or if (dumpable != 1) { /* be protective */ } Without this patch, if the system had set the sysctl fs/suid_dumpable=2, a user was able to ptrace attach to processes that had dropped privileges to that user. (This may have been partially mitigated if Yama was enabled.) The macros have been moved into the file that declares get/set_dumpable(), which means things like the ia64 code can see them too. CVE-2013-2929 Reported-by: Vasily Kulikov Signed-off-by: Kees Cook Cc: "Luck, Tony" Cc: Oleg Nesterov Cc: "Eric W. Biederman" Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

__ptrace_may_access() should not deny sub-threads

2013-09-11T22:59:01Z

__ptrace_may_access() checks get_dumpable/ptrace_has_cap/etc if task != current, this can can lead to surprising results. For example, a sub-thread can't readlink("/proc/self/exe") if the executable is not readable. setup_new_exec()->would_dump() notices that inode_permission(MAY_READ) fails and then it does set_dumpable(suid_dumpable). After that get_dumpable() fails. (It is not clear why proc_pid_readlink() checks get_dumpable(), perhaps we could add PTRACE_MODE_NODUMPABLE) Change __ptrace_may_access() to use same_thread_group() instead of "task == current". Any security check is pointless when the tasks share the same ->mm. Signed-off-by: Mark Grondona Signed-off-by: Ben Woodard Signed-off-by: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Revert "ptrace: PTRACE_DETACH should do flush_ptrace_hw_breakpoint(child)"

2013-08-06T20:16:32Z

This reverts commit fab840fc2d542fabcab903db8e03589a6702ba5f. This commit even has the test-case to prove that the tracee can be killed by SIGTRAP if the debugger does not remove the breakpoints before PTRACE_DETACH. However, this is exactly what wineserver deliberately does, set_thread_context() calls PTRACE_ATTACH + PTRACE_DETACH just for PTRACE_POKEUSER(DR*) in between. So we should revert this fix and document that PTRACE_DETACH should keep the breakpoints. Reported-by: Felipe Contreras Signed-off-by: Oleg Nesterov Signed-off-by: Linus Torvalds

ptrace: PTRACE_DETACH should do flush_ptrace_hw_breakpoint(child)

2013-07-09T17:33:26Z

Change ptrace_detach() to call flush_ptrace_hw_breakpoint(child). This frees the slots for non-ptrace PERF_TYPE_BREAKPOINT users, and this ensures that the tracee won't be killed by SIGTRAP triggered by the active breakpoints. Test-case: unsigned long encode_dr7(int drnum, int enable, unsigned int type, unsigned int len) { unsigned long dr7; dr7 = ((len | type) & 0xf) << (DR_CONTROL_SHIFT + drnum * DR_CONTROL_SIZE); if (enable) dr7 |= (DR_GLOBAL_ENABLE << (drnum * DR_ENABLE_SIZE)); return dr7; } int write_dr(int pid, int dr, unsigned long val) { return ptrace(PTRACE_POKEUSER, pid, offsetof (struct user, u_debugreg[dr]), val); } void func(void) { } int main(void) { int pid, stat; unsigned long dr7; pid = fork(); if (!pid) { assert(ptrace(PTRACE_TRACEME, 0,0,0) == 0); kill(getpid(), SIGHUP); func(); return 0x13; } assert(pid == waitpid(-1, &stat, 0)); assert(WSTOPSIG(stat) == SIGHUP); assert(write_dr(pid, 0, (long)func) == 0); dr7 = encode_dr7(0, 1, DR_RW_EXECUTE, DR_LEN_1); assert(write_dr(pid, 7, dr7) == 0); assert(ptrace(PTRACE_DETACH, pid, 0,0) == 0); assert(pid == waitpid(-1, &stat, 0)); assert(stat == 0x1300); return 0; } Before this patch the child is killed after PTRACE_DETACH. Signed-off-by: Oleg Nesterov Acked-by: Frederic Weisbecker Cc: Benjamin Herrenschmidt Cc: Ingo Molnar Cc: Jan Kratochvil Cc: Michael Neuling Cc: Paul Mackerras Cc: Paul Mundt Cc: Will Deacon Cc: Prasad Cc: Russell King Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds