1. 17 Jul, 2018 1 commit
  2. 08 Jun, 2018 1 commit
    • Yang Shi's avatar
      mm: introduce arg_lock to protect arg_start|end and env_start|end in mm_struct · 88aa7cc6
      Yang Shi authored
      mmap_sem is on the hot path of kernel, and it very contended, but it is
      abused too.  It is used to protect arg_start|end and evn_start|end when
      reading /proc/$PID/cmdline and /proc/$PID/environ, but it doesn't make
      sense since those proc files just expect to read 4 values atomically and
      not related to VM, they could be set to arbitrary values by C/R.
      
      And, the mmap_sem contention may cause unexpected issue like below:
      
      INFO: task ps:14018 blocked for more than 120 seconds.
             Tainted: G            E 4.9.79-009.ali3000.alios7.x86_64 #1
       "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this
      message.
       ps              D    0 14018      1 0x00000004
       Call Trace:
         schedule+0x36/0x80
         rwsem_down_read_failed+0xf0/0x150
         call_rwsem_down_read_failed+0x18/0x30
         down_read+0x20/0x40
         proc_pid_cmdline_read+0xd9/0x4e0
         __vfs_read+0x37/0x150
         vfs_read+0x96/0x130
         SyS_read+0x55/0xc0
         entry_SYSCALL_64_fastpath+0x1a/0xc5
      
      Both Alexey Dobriyan and Michal Hocko suggested to use dedicated lock
      for them to mitigate the abuse of mmap_sem.
      
      So, introduce a new spinlock in mm_struct to protect the concurrent
      access to arg_start|end, env_start|end and others, as well as replace
      write map_sem to read to protect the race condition between prctl and
      sys_brk which might break check_data_rlimit(), and makes prctl more
      friendly to other VM operations.
      
      This patch just eliminates the abuse of mmap_sem, but it can't resolve
      the above hung task warning completely since the later
      access_remote_vm() call needs acquire mmap_sem.  The mmap_sem
      scalability issue will be solved in the future.
      
      [[email protected]: add comment about mmap_sem and arg_lock]
        Link: http://lkml.kernel.org/r/[email protected]
      Link: http://lkml.kernel.org/r/[email protected]Signed-off-by: default avatarYang Shi <[email protected]baba.com>
      Reviewed-by: default avatarCyrill Gorcunov <[email protected]>
      Acked-by: default avatarMichal Hocko <[email protected]>
      Cc: Alexey Dobriyan <[email protected]>
      Cc: Matthew Wilcox <[email protected]>
      Cc: Mateusz Guzik <[email protected]>
      Cc: Kirill Tkhai <[email protected]>
      Signed-off-by: default avatarAndrew Morton <[email protected]>
      Signed-off-by: default avatarLinus Torvalds <[email protected]>
      88aa7cc6
  3. 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 <[email protected]>
      Reviewed-by: default avatarPhilippe Ombredanne <[email protected]>
      Reviewed-by: default avatarThomas Gleixner <[email protected]>
      Signed-off-by: default avatarGreg Kroah-Hartman <[email protected]>
      b2441318
  4. 22 Nov, 2016 1 commit
    • Eric W. Biederman's avatar
      mm: Add a user_ns owner to mm_struct and fix ptrace permission checks · bfedb589
      Eric W. Biederman authored
      During exec dumpable is cleared if the file that is being executed is
      not readable by the user executing the file.  A bug in
      ptrace_may_access allows reading the file if the executable happens to
      enter into a subordinate user namespace (aka clone(CLONE_NEWUSER),
      unshare(CLONE_NEWUSER), or setns(fd, CLONE_NEWUSER).
      
      This problem is fixed with only necessary userspace breakage by adding
      a user namespace owner to mm_struct, captured at the time of exec, so
      it is clear in which user namespace CAP_SYS_PTRACE must be present in
      to be able to safely give read permission to the executable.
      
      The function ptrace_may_access is modified to verify that the ptracer
      has CAP_SYS_ADMIN in task->mm->user_ns instead of task->cred->user_ns.
      This ensures that if the task changes it's cred into a subordinate
      user namespace it does not become ptraceable.
      
      The function ptrace_attach is modified to only set PT_PTRACE_CAP when
      CAP_SYS_PTRACE is held over task->mm->user_ns.  The intent of
      PT_PTRACE_CAP is to be a flag to note that whatever permission changes
      the task might go through the tracer has sufficient permissions for
      it not to be an issue.  task->cred->user_ns is always the same
      as or descendent of mm->user_ns.  Which guarantees that having
      CAP_SYS_PTRACE over mm->user_ns is the worst case for the tasks
      credentials.
      
      To prevent regressions mm->dumpable and mm->user_ns are not considered
      when a task has no mm.  As simply failing ptrace_may_attach causes
      regressions in privileged applications attempting to read things
      such as /proc/<pid>/stat
      
      Cc: [email protected]
      Acked-by: default avatarKees Cook <[email protected]>
      Tested-by: default avatarCyrill Gorcunov <[email protected]>
      Fixes: 8409cca7 ("userns: allow ptrace from non-init user namespaces")
      Signed-off-by: default avatar"Eric W. Biederman" <[email protected]>
      bfedb589
  5. 26 Jul, 2011 1 commit
  6. 25 May, 2011 1 commit
  7. 10 Aug, 2010 1 commit
  8. 17 Jun, 2009 1 commit