1. 02 Nov, 2017 1 commit
    • Greg Kroah-Hartman's avatar
      License cleanup: add SPDX GPL-2.0 license identifier to files with no license · b2441318
      Greg Kroah-Hartman authored
      Many source files in the tree are missing licensing information, which
      makes it harder for compliance tools to determine the correct license.
      
      By default all files without license information are under the default
      license of the kernel, which is GPL version 2.
      
      Update the files which contain no license information with the 'GPL-2.0'
      SPDX license identifier.  The SPDX identifier is a legally binding
      shorthand, which can be used instead of the full boiler plate text.
      
      This patch is based on work done by Thomas Gleixner and Kate Stewart and
      Philippe Ombredanne.
      
      How this work was done:
      
      Patches were generated and checked against linux-4.14-rc6 for a subset of
      the use cases:
       - file had no licensing information it it.
       - file was a */uapi/* one with no licensing information in it,
       - file was a */uapi/* one with existing licensing information,
      
      Further patches will be generated in subsequent months to fix up cases
      where non-standard license headers were used, and references to license
      had to be inferred by heuristics based on keywords.
      
      The analysis to determine which SPDX License Identifier to be applied to
      a file was done in a spreadsheet of side by side results from of the
      output of two independent scanners (ScanCode & Windriver) producing SPDX
      tag:value files created by Philippe Ombredanne.  Philippe prepared the
      base worksheet, and did an initial spot review of a few 1000 files.
      
      The 4.13 kernel was the starting point of the analysis with 60,537 files
      assessed.  Kate Stewart did a file by file comparison of the scanner
      results in the spreadsheet to determine which SPDX license identifier(s)
      to be applied to the file. She confirmed any determination that was not
      immediately clear with lawyers working with the Linux Foundation.
      
      Criteria used to select files for SPDX license identifier tagging was:
       - Files considered eligible had to be source code files.
       - Make and config files were included as candidates if they contained >5
         lines of source
       - File already had some variant of a license header in it (even if <5
         lines).
      
      All documentation files were explicitly excluded.
      
      The following heuristics were used to determine which SPDX license
      identifiers to apply.
      
       - when both scanners couldn't find any license traces, file was
         considered to have no license information in it, and the top level
         COPYING file license applied.
      
         For non */uapi/* files that summary was:
      
         SPDX license identifier                            # files
         ---------------------------------------------------|-------
         GPL-2.0                                              11139
      
         and resulted in the first patch in this series.
      
         If that file was a */uapi/* path one, it was "GPL-2.0 WITH
         Linux-syscall-note" otherwise it was "GPL-2.0".  Results of that was:
      
         SPDX license identifier                            # files
         ---------------------------------------------------|-------
         GPL-2.0 WITH Linux-syscall-note                        930
      
         and resulted in the second patch in this series.
      
       - if a file had some form of licensing information in it, and was one
         of the */uapi/* ones, it was denoted with the Linux-syscall-note if
         any GPL family license was found in the file or had no licensing in
         it (per prior point).  Results summary:
      
         SPDX license identifier                            # files
         ---------------------------------------------------|------
         GPL-2.0 WITH Linux-syscall-note                       270
         GPL-2.0+ WITH Linux-syscall-note                      169
         ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause)    21
         ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)    17
         LGPL-2.1+ WITH Linux-syscall-note                      15
         GPL-1.0+ WITH Linux-syscall-note                       14
         ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause)    5
         LGPL-2.0+ WITH Linux-syscall-note                       4
         LGPL-2.1 WITH Linux-syscall-note                        3
         ((GPL-2.0 WITH Linux-syscall-note) OR MIT)              3
         ((GPL-2.0 WITH Linux-syscall-note) AND MIT)             1
      
         and that resulted in the third patch in this series.
      
       - when the two scanners agreed on the detected license(s), that became
         the concluded license(s).
      
       - when there was disagreement between the two scanners (one detected a
         license but the other didn't, or they both detected different
         licenses) a manual inspection of the file occurred.
      
       - In most cases a manual inspection of the information in the file
         resulted in a clear resolution of the license that should apply (and
         which scanner probably needed to revisit its heuristics).
      
       - When it was not immediately clear, the license identifier was
         confirmed with lawyers working with the Linux Foundation.
      
       - If there was any question as to the appropriate license identifier,
         the file was flagged for further research and to be revisited later
         in time.
      
      In total, over 70 hours of logged manual review was done on the
      spreadsheet to determine the SPDX license identifiers to apply to the
      source files by Kate, Philippe, Thomas and, in some cases, confirmation
      by lawyers working with the Linux Foundation.
      
      Kate also obtained a third independent scan of the 4.13 code base from
      FOSSology, and compared selected files where the other two scanners
      disagreed against that SPDX file, to see if there was new insights.  The
      Windriver scanner is based on an older version of FOSSology in part, so
      they are related.
      
      Thomas did random spot checks in about 500 files from the spreadsheets
      for the uapi headers and agreed with SPDX license identifier in the
      files he inspected. For the non-uapi files Thomas did random spot checks
      in about 15000 files.
      
      In initial set of patches against 4.14-rc6, 3 files were found to have
      copy/paste license identifier errors, and have been fixed to reflect the
      correct identifier.
      
      Additionally Philippe spent 10 hours this week doing a detailed manual
      inspection and review of the 12,461 patched files from the initial patch
      version early this week with:
       - a full scancode scan run, collecting the matched texts, detected
         license ids and scores
       - reviewing anything where there was a license detected (about 500+
         files) to ensure that the applied SPDX license was correct
       - reviewing anything where there was no detection but the patch license
         was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
         SPDX license was correct
      
      This produced a worksheet with 20 files needing minor correction.  This
      worksheet was then exported into 3 different .csv files for the
      different types of files to be modified.
      
      These .csv files were then reviewed by Greg.  Thomas wrote a script to
      parse the csv files and add the proper SPDX tag to the file, in the
      format that the file expected.  This script was further refined by Greg
      based on the output to detect more types of files automatically and to
      distinguish between header and source .c files (which need different
      comment types.)  Finally Greg ran the script using the .csv files to
      generate the patches.
      Reviewed-by: default avatarKate Stewart <kstewart@linuxfoundation.org>
      Reviewed-by: default avatarPhilippe Ombredanne <pombredanne@nexb.com>
      Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      b2441318
  2. 04 Oct, 2017 1 commit
  3. 12 Jul, 2017 1 commit
    • Cyrill Gorcunov's avatar
      kcmp: add KCMP_EPOLL_TFD mode to compare epoll target files · 0791e364
      Cyrill Gorcunov authored
      With current epoll architecture target files are addressed with
      file_struct and file descriptor number, where the last is not unique.
      Moreover files can be transferred from another process via unix socket,
      added into queue and closed then so we won't find this descriptor in the
      task fdinfo list.
      
      Thus to checkpoint and restore such processes CRIU needs to find out
      where exactly the target file is present to add it into epoll queue.
      For this sake one can use kcmp call where some particular target file
      from the queue is compared with arbitrary file passed as an argument.
      
      Because epoll target files can have same file descriptor number but
      different file_struct a caller should explicitly specify the offset
      within.
      
      To test if some particular file is matching entry inside epoll one have
      to
      
       - fill kcmp_epoll_slot structure with epoll file descriptor,
         target file number and target file offset (in case if only
         one target is present then it should be 0)
      
       - call kcmp as kcmp(pid1, pid2, KCMP_EPOLL_TFD, fd, &kcmp_epoll_slot)
          - the kernel fetch file pointer matching file descriptor @fd of pid1
          - lookups for file struct in epoll queue of pid2 and returns traditional
            0,1,2 result for sorting purpose
      
      Link: http://lkml.kernel.org/r/20170424154423.511592110@gmail.comSigned-off-by: default avatarCyrill Gorcunov <gorcunov@openvz.org>
      Acked-by: default avatarAndrey Vagin <avagin@openvz.org>
      Cc: Al Viro <viro@zeniv.linux.org.uk>
      Cc: Pavel Emelyanov <xemul@virtuozzo.com>
      Cc: Michael Kerrisk <mtk.manpages@gmail.com>
      Cc: Jason Baron <jbaron@akamai.com>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      0791e364
  4. 21 Jan, 2016 1 commit
    • Jann Horn's avatar
      ptrace: use fsuid, fsgid, effective creds for fs access checks · caaee623
      Jann Horn authored
      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: default avatarJann Horn <jann@thejh.net>
      Acked-by: default avatarKees Cook <keescook@chromium.org>
      Cc: Casey Schaufler <casey@schaufler-ca.com>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: James Morris <james.l.morris@oracle.com>
      Cc: "Serge E. Hallyn" <serge.hallyn@ubuntu.com>
      Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
      Cc: Andy Lutomirski <luto@kernel.org>
      Cc: Al Viro <viro@zeniv.linux.org.uk>
      Cc: "Eric W. Biederman" <ebiederm@xmission.com>
      Cc: Willy Tarreau <w@1wt.eu>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      caaee623
  5. 10 Sep, 2014 1 commit
    • Rasmus Villemoes's avatar
      kcmp: fix standard comparison bug · acbbe6fb
      Rasmus Villemoes authored
      The C operator <= defines a perfectly fine total ordering on the set of
      values representable in a long.  However, unlike its namesake in the
      integers, it is not translation invariant, meaning that we do not have
      "b <= c" iff "a+b <= a+c" for all a,b,c.
      
      This means that it is always wrong to try to boil down the relationship
      between two longs to a question about the sign of their difference,
      because the resulting relation [a LEQ b iff a-b <= 0] is neither
      anti-symmetric or transitive.  The former is due to -LONG_MIN==LONG_MIN
      (take any two a,b with a-b = LONG_MIN; then a LEQ b and b LEQ a, but a !=
      b).  The latter can either be seen observing that x LEQ x+1 for all x,
      implying x LEQ x+1 LEQ x+2 ...  LEQ x-1 LEQ x; or more directly with the
      simple example a=LONG_MIN, b=0, c=1, for which a-b < 0, b-c < 0, but a-c >
      0.
      
      Note that it makes absolutely no difference that a transmogrying bijection
      has been applied before the comparison is done.  In fact, had the
      obfuscation not been done, one could probably not observe the bug
      (assuming all values being compared always lie in one half of the address
      space, the mathematical value of a-b is always representable in a long).
      As it stands, one can easily obtain three file descriptors exhibiting the
      non-transitivity of kcmp().
      
      Side note 1: I can't see that ensuring the MSB of the multiplier is
      set serves any purpose other than obfuscating the obfuscating code.
      
      Side note 2:
      #include <stdio.h>
      #include <stdlib.h>
      #include <string.h>
      #include <fcntl.h>
      #include <unistd.h>
      #include <assert.h>
      #include <sys/syscall.h>
      
      enum kcmp_type {
              KCMP_FILE,
              KCMP_VM,
              KCMP_FILES,
              KCMP_FS,
              KCMP_SIGHAND,
              KCMP_IO,
              KCMP_SYSVSEM,
              KCMP_TYPES,
      };
      pid_t pid;
      
      int kcmp(pid_t pid1, pid_t pid2, int type,
      	 unsigned long idx1, unsigned long idx2)
      {
      	return syscall(SYS_kcmp, pid1, pid2, type, idx1, idx2);
      }
      int cmp_fd(int fd1, int fd2)
      {
      	int c = kcmp(pid, pid, KCMP_FILE, fd1, fd2);
      	if (c < 0) {
      		perror("kcmp");
      		exit(1);
      	}
      	assert(0 <= c && c < 3);
      	return c;
      }
      int cmp_fdp(const void *a, const void *b)
      {
      	static const int normalize[] = {0, -1, 1};
      	return normalize[cmp_fd(*(int*)a, *(int*)b)];
      }
      #define MAX 100 /* This is plenty; I've seen it trigger for MAX==3 */
      int main(int argc, char *argv[])
      {
      	int r, s, count = 0;
      	int REL[3] = {0,0,0};
      	int fd[MAX];
      	pid = getpid();
      	while (count < MAX) {
      		r = open("/dev/null", O_RDONLY);
      		if (r < 0)
      			break;
      		fd[count++] = r;
      	}
      	printf("opened %d file descriptors\n", count);
      	for (r = 0; r < count; ++r) {
      		for (s = r+1; s < count; ++s) {
      			REL[cmp_fd(fd[r], fd[s])]++;
      		}
      	}
      	printf("== %d\t< %d\t> %d\n", REL[0], REL[1], REL[2]);
      	qsort(fd, count, sizeof(fd[0]), cmp_fdp);
      	memset(REL, 0, sizeof(REL));
      
      	for (r = 0; r < count; ++r) {
      		for (s = r+1; s < count; ++s) {
      			REL[cmp_fd(fd[r], fd[s])]++;
      		}
      	}
      	printf("== %d\t< %d\t> %d\n", REL[0], REL[1], REL[2]);
      	return (REL[0] + REL[2] != 0);
      }
      Signed-off-by: default avatarRasmus Villemoes <linux@rasmusvillemoes.dk>
      Reviewed-by: default avatarCyrill Gorcunov <gorcunov@openvz.org>
      "Eric W. Biederman" <ebiederm@xmission.com>
      Cc: <stable@vger.kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      acbbe6fb
  6. 21 Dec, 2012 1 commit
  7. 01 Jun, 2012 1 commit
    • Cyrill Gorcunov's avatar
      syscalls, x86: add __NR_kcmp syscall · d97b46a6
      Cyrill Gorcunov authored
      While doing the checkpoint-restore in the user space one need to determine
      whether various kernel objects (like mm_struct-s of file_struct-s) are
      shared between tasks and restore this state.
      
      The 2nd step can be solved by using appropriate CLONE_ flags and the
      unshare syscall, while there's currently no ways for solving the 1st one.
      
      One of the ways for checking whether two tasks share e.g.  mm_struct is to
      provide some mm_struct ID of a task to its proc file, but showing such
      info considered to be not that good for security reasons.
      
      Thus after some debates we end up in conclusion that using that named
      'comparison' syscall might be the best candidate.  So here is it --
      __NR_kcmp.
      
      It takes up to 5 arguments - the pids of the two tasks (which
      characteristics should be compared), the comparison type and (in case of
      comparison of files) two file descriptors.
      
      Lookups for pids are done in the caller's PID namespace only.
      
      At moment only x86 is supported and tested.
      
      [akpm@linux-foundation.org: fix up selftests, warnings]
      [akpm@linux-foundation.org: include errno.h]
      [akpm@linux-foundation.org: tweak comment text]
      Signed-off-by: default avatarCyrill Gorcunov <gorcunov@openvz.org>
      Acked-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
      Cc: Pavel Emelyanov <xemul@parallels.com>
      Cc: Andrey Vagin <avagin@openvz.org>
      Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Glauber Costa <glommer@parallels.com>
      Cc: Andi Kleen <andi@firstfloor.org>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Matt Helsley <matthltc@us.ibm.com>
      Cc: Pekka Enberg <penberg@kernel.org>
      Cc: Eric Dumazet <eric.dumazet@gmail.com>
      Cc: Vasiliy Kulikov <segoon@openwall.com>
      Cc: Alexey Dobriyan <adobriyan@gmail.com>
      Cc: Valdis.Kletnieks@vt.edu
      Cc: Michal Marek <mmarek@suse.cz>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      d97b46a6