linux/kernel/ptrace.c, branch v4.9

mm: replace access_process_vm() write parameter with gup_flags

2016-10-19T15:31:25Z

This removes the 'write' argument from access_process_vm() and replaces it with 'gup_flags' as use of this function previously silently implied FOLL_FORCE, whereas after this patch callers explicitly pass this flag. We make this explicit as use of FOLL_FORCE can result in surprising behaviour (and hence bugs) within the mm subsystem. Signed-off-by: Lorenzo Stoakes Acked-by: Jesper Nilsson Acked-by: Michal Hocko Acked-by: Michael Ellerman Signed-off-by: Linus Torvalds

ptrace: clear TIF_SYSCALL_TRACE on ptrace detach

2016-10-11T22:06:32Z

On __ptrace_detach(), called from do_exit()->exit_notify()-> forget_original_parent()->exit_ptrace(), the TIF_SYSCALL_TRACE in thread->flags of the tracee is not cleared up. This results in the tracehook_report_syscall_* being called (though there's no longer a tracer listening to that) upon its further syscalls. Example scenario - attach "strace" to a running process and kill it (the strace) with SIGKILL. You'll see that the syscall trace hooks are still being called. The clearing of this flag should be moved from ptrace_detach() to __ptrace_detach(). Link: http://lkml.kernel.org/r/1472759493-20554-1-git-send-email-alnovak@suse.cz Signed-off-by: Ales Novak Acked-by: Oleg Nesterov Cc: Jiri Kosina Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

tree-wide: replace config_enabled() with IS_ENABLED()

2016-08-04T12:50:07Z

The use of config_enabled() against config options is ambiguous. In practical terms, config_enabled() is equivalent to IS_BUILTIN(), but the author might have used it for the meaning of IS_ENABLED(). Using IS_ENABLED(), IS_BUILTIN(), IS_MODULE() etc. makes the intention clearer. This commit replaces config_enabled() with IS_ENABLED() where possible. This commit is only touching bool config options. I noticed two cases where config_enabled() is used against a tristate option: - config_enabled(CONFIG_HWMON) [ drivers/net/wireless/ath/ath10k/thermal.c ] - config_enabled(CONFIG_BACKLIGHT_CLASS_DEVICE) [ drivers/gpu/drm/gma500/opregion.c ] I did not touch them because they should be converted to IS_BUILTIN() in order to keep the logic, but I was not sure it was the authors' intention. Link: http://lkml.kernel.org/r/1465215656-20569-1-git-send-email-yamada.masahiro@socionext.com Signed-off-by: Masahiro Yamada Acked-by: Kees Cook Cc: Stas Sergeev Cc: Matt Redfearn Cc: Joshua Kinard Cc: Jiri Slaby Cc: Bjorn Helgaas Cc: Borislav Petkov Cc: Markos Chandras Cc: "Dmitry V. Levin" Cc: yu-cheng yu Cc: James Hogan Cc: Brian Gerst Cc: Johannes Berg Cc: Peter Zijlstra Cc: Al Viro Cc: Will Drewry Cc: Nikolay Martynov Cc: Huacai Chen Cc: "H. Peter Anvin" Cc: Thomas Gleixner Cc: Daniel Borkmann Cc: Leonid Yegoshin Cc: Rafal Milecki Cc: James Cowgill Cc: Greg Kroah-Hartman Cc: Ralf Baechle Cc: Alex Smith Cc: Adam Buchbinder Cc: Qais Yousef Cc: Jiang Liu Cc: Mikko Rapeli Cc: Paul Gortmaker Cc: Denys Vlasenko Cc: Brian Norris Cc: Hidehiro Kawai Cc: "Luis R. Rodriguez" Cc: Andy Lutomirski Cc: Ingo Molnar Cc: Dave Hansen Cc: "Kirill A. Shutemov" Cc: Roland McGrath Cc: Paul Burton Cc: Kalle Valo Cc: Viresh Kumar Cc: Tony Wu Cc: Huaitong Han Cc: Sumit Semwal Cc: Alexei Starovoitov Cc: Juergen Gross Cc: Jason Cooper Cc: "David S. Miller" Cc: Oleg Nesterov Cc: Andrea Gelmini Cc: David Woodhouse Cc: Marc Zyngier Cc: Rabin Vincent Cc: "Maciej W. Rozycki" Cc: David Daney Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ptrace: change __ptrace_unlink() to clear ->ptrace under ->siglock

2016-03-22T22:36:02Z

This test-case (simplified version of generated by syzkaller) #include #include #include void test(void) { for (;;) { if (fork()) { wait(NULL); continue; } ptrace(PTRACE_SEIZE, getppid(), 0, 0); ptrace(PTRACE_INTERRUPT, getppid(), 0, 0); _exit(0); } } int main(void) { int np; for (np = 0; np < 8; ++np) if (!fork()) test(); while (wait(NULL) > 0) ; return 0; } triggers the 2nd WARN_ON_ONCE(!signr) warning in do_jobctl_trap(). The problem is that __ptrace_unlink() clears task->jobctl under siglock but task->ptrace is cleared without this lock held; this fools the "else" branch which assumes that !PT_SEIZED means PT_PTRACED. Note also that most of other PTRACE_SEIZE checks can race with detach from the exiting tracer too. Say, the callers of ptrace_trap_notify() assume that SEIZED can't go away after it was checked. Signed-off-by: Oleg Nesterov Reported-by: Dmitry Vyukov Cc: Tejun Heo Cc: syzkaller Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ptrace: in PEEK_SIGINFO, check syscall bitness, not task bitness

2016-03-22T22:36:02Z

Users of the 32-bit ptrace() ABI expect the full 32-bit ABI. siginfo translation should check ptrace() ABI, not caller task ABI. This is an ABI change on SPARC. Let's hope that no one relied on the old buggy ABI. Signed-off-by: Andy Lutomirski Cc: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ptrace: use fsuid, fsgid, effective creds for fs access checks

2016-01-21T01:09:18Z

By checking the effective credentials instead of the real UID / permitted capabilities, ensure that the calling process actually intended to use its credentials. To ensure that all ptrace checks use the correct caller credentials (e.g. in case out-of-tree code or newly added code omits the PTRACE_MODE_*CREDS flag), use two new flags and require one of them to be set. The problem was that when a privileged task had temporarily dropped its privileges, e.g. by calling setreuid(0, user_uid), with the intent to perform following syscalls with the credentials of a user, it still passed ptrace access checks that the user would not be able to pass. While an attacker should not be able to convince the privileged task to perform a ptrace() syscall, this is a problem because the ptrace access check is reused for things in procfs. In particular, the following somewhat interesting procfs entries only rely on ptrace access checks: /proc/$pid/stat - uses the check for determining whether pointers should be visible, useful for bypassing ASLR /proc/$pid/maps - also useful for bypassing ASLR /proc/$pid/cwd - useful for gaining access to restricted directories that contain files with lax permissions, e.g. in this scenario: lrwxrwxrwx root root /proc/13020/cwd -> /root/foobar drwx------ root root /root drwxr-xr-x root root /root/foobar -rw-r--r-- root root /root/foobar/secret Therefore, on a system where a root-owned mode 6755 binary changes its effective credentials as described and then dumps a user-specified file, this could be used by an attacker to reveal the memory layout of root's processes or reveal the contents of files he is not allowed to access (through /proc/$pid/cwd). [akpm@linux-foundation.org: fix warning] Signed-off-by: Jann Horn Acked-by: Kees Cook Cc: Casey Schaufler Cc: Oleg Nesterov Cc: Ingo Molnar Cc: James Morris Cc: "Serge E. Hallyn" Cc: Andy Shevchenko Cc: Andy Lutomirski Cc: Al Viro Cc: "Eric W. Biederman" Cc: Willy Tarreau Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ptrace: make wait_on_bit(JOBCTL_TRAPPING_BIT) in ptrace_attach() killable

2016-01-21T01:09:18Z

ptrace_attach() can hang waiting for STOPPED -> TRACED transition if the tracee gets frozen in between, change wait_on_bit() to use TASK_KILLABLE. This doesn't really solve the problem(s) and we probably need to fix the freezer. In particular, note that this means that pm freezer will fail if it races attach-to-stopped-task. And otoh perhaps we can just remove JOBCTL_TRAPPING_BIT altogether, it is not clear if we really need to hide this transition from debugger, WNOHANG after PTRACE_ATTACH can fail anyway if it races with SIGCONT. Signed-off-by: Oleg Nesterov Reported-by: Andrey Ryabinin Cc: Roland McGrath Acked-by: Tejun Heo Cc: Pedro Alves Cc: Jan Kratochvil Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

seccomp, ptrace: add support for dumping seccomp filters

2015-10-28T02:55:13Z

This patch adds support for dumping a process' (classic BPF) seccomp filters via ptrace. PTRACE_SECCOMP_GET_FILTER allows the tracer to dump the user's classic BPF seccomp filters. addr should be an integer which represents the ith seccomp filter (0 is the most recently installed filter). data should be a struct sock_filter * with enough room for the ith filter, or NULL, in which case the filter is not saved. The return value for this command is the number of BPF instructions the program represents, or negative in the case of errors. Command specific errors are ENOENT: which indicates that there is no ith filter in this seccomp tree, and EMEDIUMTYPE, which indicates that the ith filter was not installed as a classic BPF filter. A caveat with this approach is that there is no way to get explicitly at the heirarchy of seccomp filters, and users need to memcmp() filters to decide which are inherited. This means that a task which installs two of the same filter can potentially confuse users of this interface. v2: * make save_orig const * check that the orig_prog exists (not necessary right now, but when grows eBPF support it will be) * s/n/filter_off and make it an unsigned long to match ptrace * count "down" the tree instead of "up" when passing a filter offset v3: * don't take the current task's lock for inspecting its seccomp mode * use a 0x42** constant for the ptrace command value v4: * don't copy to userspace while holding spinlocks v5: * add another condition to WARN_ON v6: * rebase on net-next Signed-off-by: Tycho Andersen Acked-by: Kees Cook CC: Will Drewry Reviewed-by: Oleg Nesterov CC: Andy Lutomirski CC: Pavel Emelyanov CC: Serge E. Hallyn CC: Alexei Starovoitov CC: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller

seccomp: add ptrace options for suspend/resume

2015-07-15T18:52:52Z

This patch is the first step in enabling checkpoint/restore of processes with seccomp enabled. One of the things CRIU does while dumping tasks is inject code into them via ptrace to collect information that is only available to the process itself. However, if we are in a seccomp mode where these processes are prohibited from making these syscalls, then what CRIU does kills the task. This patch adds a new ptrace option, PTRACE_O_SUSPEND_SECCOMP, that enables a task from the init user namespace which has CAP_SYS_ADMIN and no seccomp filters to disable (and re-enable) seccomp filters for another task so that they can be successfully dumped (and restored). We restrict the set of processes that can disable seccomp through ptrace because although today ptrace can be used to bypass seccomp, there is some discussion of closing this loophole in the future and we would like this patch to not depend on that behavior and be future proofed for when it is removed. Note that seccomp can be suspended before any filters are actually installed; this behavior is useful on criu restore, so that we can suspend seccomp, restore the filters, unmap our restore code from the restored process' address space, and then resume the task by detaching and have the filters resumed as well. v2 changes: * require that the tracer have no seccomp filters installed * drop TIF_NOTSC manipulation from the patch * change from ptrace command to a ptrace option and use this ptrace option as the flag to check. This means that as soon as the tracer detaches/dies, seccomp is re-enabled and as a corrollary that one can not disable seccomp across PTRACE_ATTACHs. v3 changes: * get rid of various #ifdefs everywhere * report more sensible errors when PTRACE_O_SUSPEND_SECCOMP is incorrectly used v4 changes: * get rid of may_suspend_seccomp() in favor of a capable() check in ptrace directly v5 changes: * check that seccomp is not enabled (or suspended) on the tracer Signed-off-by: Tycho Andersen CC: Will Drewry CC: Roland McGrath CC: Pavel Emelyanov CC: Serge E. Hallyn Acked-by: Oleg Nesterov Acked-by: Andy Lutomirski [kees: access seccomp.mode through seccomp_mode() instead] Signed-off-by: Kees Cook

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