1. 04 Oct, 2017 1 commit
  2. 13 Dec, 2014 1 commit
    • David Drysdale's avatar
      syscalls: implement execveat() system call · 51f39a1f
      David Drysdale authored
      This patchset adds execveat(2) for x86, and is derived from Meredydd
      Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528).
      The primary aim of adding an execveat syscall is to allow an
      implementation of fexecve(3) that does not rely on the /proc filesystem,
      at least for executables (rather than scripts).  The current glibc version
      of fexecve(3) is implemented via /proc, which causes problems in sandboxed
      or otherwise restricted environments.
      Given the desire for a /proc-free fexecve() implementation, HPA suggested
      (https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be
      an appropriate generalization.
      Also, having a new syscall means that it can take a flags argument without
      back-compatibility concerns.  The current implementation just defines the
      AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW flags, but other flags could be
      added in future -- for example, flags for new namespaces (as suggested at
      Related history:
       - https://lkml.org/lkml/2006/12/27/123 is an example of someone
         realizing that fexecve() is likely to fail in a chroot environment.
       - http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered
         documenting the /proc requirement of fexecve(3) in its manpage, to
         "prevent other people from wasting their time".
       - https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a
         problem where a process that did setuid() could not fexecve()
         because it no longer had access to /proc/self/fd; this has since
         been fixed.
      This patch (of 4):
      Add a new execveat(2) system call.  execveat() is to execve() as openat()
      is to open(): it takes a file descriptor that refers to a directory, and
      resolves the filename relative to that.
      In addition, if the filename is empty and AT_EMPTY_PATH is specified,
      execveat() executes the file to which the file descriptor refers.  This
      replicates the functionality of fexecve(), which is a system call in other
      UNIXen, but in Linux glibc it depends on opening "/proc/self/fd/<fd>" (and
      so relies on /proc being mounted).
      The filename fed to the executed program as argv[0] (or the name of the
      script fed to a script interpreter) will be of the form "/dev/fd/<fd>"
      (for an empty filename) or "/dev/fd/<fd>/<filename>", effectively
      reflecting how the executable was found.  This does however mean that
      execution of a script in a /proc-less environment won't work; also, script
      execution via an O_CLOEXEC file descriptor fails (as the file will not be
      accessible after exec).
      Based on patches by Meredydd Luff.
      Signed-off-by: 's avatarDavid Drysdale <drysdale@google.com>
      Cc: Meredydd Luff <meredydd@senatehouse.org>
      Cc: Shuah Khan <shuah.kh@samsung.com>
      Cc: "Eric W. Biederman" <ebiederm@xmission.com>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Alexander Viro <viro@zeniv.linux.org.uk>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: "H. Peter Anvin" <hpa@zytor.com>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: Arnd Bergmann <arnd@arndb.de>
      Cc: Rich Felker <dalias@aerifal.cx>
      Cc: Christoph Hellwig <hch@infradead.org>
      Cc: Michael Kerrisk <mtk.manpages@gmail.com>
      Signed-off-by: 's avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
  3. 21 Dec, 2012 1 commit
    • Kees Cook's avatar
      exec: do not leave bprm->interp on stack · b66c5984
      Kees Cook authored
      If a series of scripts are executed, each triggering module loading via
      unprintable bytes in the script header, kernel stack contents can leak
      into the command line.
      Normally execution of binfmt_script and binfmt_misc happens recursively.
      However, when modules are enabled, and unprintable bytes exist in the
      bprm->buf, execution will restart after attempting to load matching
      binfmt modules.  Unfortunately, the logic in binfmt_script and
      binfmt_misc does not expect to get restarted.  They leave bprm->interp
      pointing to their local stack.  This means on restart bprm->interp is
      left pointing into unused stack memory which can then be copied into the
      userspace argv areas.
      After additional study, it seems that both recursion and restart remains
      the desirable way to handle exec with scripts, misc, and modules.  As
      such, we need to protect the changes to interp.
      This changes the logic to require allocation for any changes to the
      bprm->interp.  To avoid adding a new kmalloc to every exec, the default
      value is left as-is.  Only when passing through binfmt_script or
      binfmt_misc does an allocation take place.
      For a proof of concept, see DoTest.sh from:
         http://www.halfdog.net/Security/2012/LinuxKernelBinfmtScriptStackDataDisclosure/Signed-off-by: 's avatarKees Cook <keescook@chromium.org>
      Cc: halfdog <me@halfdog.net>
      Cc: P J P <ppandit@redhat.com>
      Cc: Alexander Viro <viro@zeniv.linux.org.uk>
      Cc: <stable@vger.kernel.org>
      Signed-off-by: 's avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
  4. 18 Dec, 2012 1 commit
    • Kees Cook's avatar
      exec: use -ELOOP for max recursion depth · d7402698
      Kees Cook authored
      To avoid an explosion of request_module calls on a chain of abusive
      scripts, fail maximum recursion with -ELOOP instead of -ENOEXEC. As soon
      as maximum recursion depth is hit, the error will fail all the way back
      up the chain, aborting immediately.
      This also has the side-effect of stopping the user's shell from attempting
      to reexecute the top-level file as a shell script. As seen in the
      dash source:
              if (cmd != path_bshell && errno == ENOEXEC) {
                      *argv-- = cmd;
                      *argv = cmd = path_bshell;
                      goto repeat;
      The above logic was designed for running scripts automatically that lacked
      the "#!" header, not to re-try failed recursion. On a legitimate -ENOEXEC,
      things continue to behave as the shell expects.
      Additionally, when tracking recursion, the binfmt handlers should not be
      involved. The recursion being tracked is the depth of calls through
      search_binary_handler(), so that function should be exclusively responsible
      for tracking the depth.
      Signed-off-by: 's avatarKees Cook <keescook@chromium.org>
      Cc: halfdog <me@halfdog.net>
      Cc: P J P <ppandit@redhat.com>
      Cc: Alexander Viro <viro@zeniv.linux.org.uk>
      Signed-off-by: 's avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
  5. 29 Nov, 2012 2 commits
  6. 21 Mar, 2012 1 commit
  7. 18 Aug, 2010 1 commit
    • David Howells's avatar
      Make do_execve() take a const filename pointer · d7627467
      David Howells authored
      Make do_execve() take a const filename pointer so that kernel_execve() compiles
      correctly on ARM:
      arch/arm/kernel/sys_arm.c:88: warning: passing argument 1 of 'do_execve' discards qualifiers from pointer target type
      This also requires the argv and envp arguments to be consted twice, once for
      the pointer array and once for the strings the array points to.  This is
      because do_execve() passes a pointer to the filename (now const) to
      copy_strings_kernel().  A simpler alternative would be to cast the filename
      pointer in do_execve() when it's passed to copy_strings_kernel().
      do_execve() may not change any of the strings it is passed as part of the argv
      or envp lists as they are some of them in .rodata, so marking these strings as
      const should be fine.
      Further kernel_execve() and sys_execve() need to be changed to match.
      This has been test built on x86_64, frv, arm and mips.
      Signed-off-by: 's avatarDavid Howells <dhowells@redhat.com>
      Tested-by: 's avatarRalf Baechle <ralf@linux-mips.org>
      Acked-by: 's avatarRussell King <rmk+kernel@arm.linux.org.uk>
      Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
  8. 30 Mar, 2010 1 commit
    • Tejun Heo's avatar
      include cleanup: Update gfp.h and slab.h includes to prepare for breaking... · 5a0e3ad6
      Tejun Heo authored
      include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h
      percpu.h is included by sched.h and module.h and thus ends up being
      included when building most .c files.  percpu.h includes slab.h which
      in turn includes gfp.h making everything defined by the two files
      universally available and complicating inclusion dependencies.
      percpu.h -> slab.h dependency is about to be removed.  Prepare for
      this change by updating users of gfp and slab facilities include those
      headers directly instead of assuming availability.  As this conversion
      needs to touch large number of source files, the following script is
      used as the basis of conversion.
      The script does the followings.
      * Scan files for gfp and slab usages and update includes such that
        only the necessary includes are there.  ie. if only gfp is used,
        gfp.h, if slab is used, slab.h.
      * When the script inserts a new include, it looks at the include
        blocks and try to put the new include such that its order conforms
        to its surrounding.  It's put in the include block which contains
        core kernel includes, in the same order that the rest are ordered -
        alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
        doesn't seem to be any matching order.
      * If the script can't find a place to put a new include (mostly
        because the file doesn't have fitting include block), it prints out
        an error message indicating which .h file needs to be added to the
      The conversion was done in the following steps.
      1. The initial automatic conversion of all .c files updated slightly
         over 4000 files, deleting around 700 includes and adding ~480 gfp.h
         and ~3000 slab.h inclusions.  The script emitted errors for ~400
      2. Each error was manually checked.  Some didn't need the inclusion,
         some needed manual addition while adding it to implementation .h or
         embedding .c file was more appropriate for others.  This step added
         inclusions to around 150 files.
      3. The script was run again and the output was compared to the edits
         from #2 to make sure no file was left behind.
      4. Several build tests were done and a couple of problems were fixed.
         e.g. lib/decompress_*.c used malloc/free() wrappers around slab
         APIs requiring slab.h to be added manually.
      5. The script was run on all .h files but without automatically
         editing them as sprinkling gfp.h and slab.h inclusions around .h
         files could easily lead to inclusion dependency hell.  Most gfp.h
         inclusion directives were ignored as stuff from gfp.h was usually
         wildly available and often used in preprocessor macros.  Each
         slab.h inclusion directive was examined and added manually as
      6. percpu.h was updated not to include slab.h.
      7. Build test were done on the following configurations and failures
         were fixed.  CONFIG_GCOV_KERNEL was turned off for all tests (as my
         distributed build env didn't work with gcov compiles) and a few
         more options had to be turned off depending on archs to make things
         build (like ipr on powerpc/64 which failed due to missing writeq).
         * x86 and x86_64 UP and SMP allmodconfig and a custom test config.
         * powerpc and powerpc64 SMP allmodconfig
         * sparc and sparc64 SMP allmodconfig
         * ia64 SMP allmodconfig
         * s390 SMP allmodconfig
         * alpha SMP allmodconfig
         * um on x86_64 SMP allmodconfig
      8. percpu.h modifications were reverted so that it could be applied as
         a separate patch and serve as bisection point.
      Given the fact that I had only a couple of failures from tests on step
      6, I'm fairly confident about the coverage of this conversion patch.
      If there is a breakage, it's likely to be something in one of the arch
      headers which should be easily discoverable easily on most builds of
      the specific arch.
      Signed-off-by: 's avatarTejun Heo <tj@kernel.org>
      Guess-its-ok-by: 's avatarChristoph Lameter <cl@linux-foundation.org>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
  9. 16 Oct, 2008 1 commit
    • Kirill A. Shutemov's avatar
      Allow recursion in binfmt_script and binfmt_misc · bf2a9a39
      Kirill A. Shutemov authored
      binfmt_script and binfmt_misc disallow recursion to avoid stack overflow
      using sh_bang and misc_bang.  It causes problem in some cases:
      $ echo '#!/bin/ls' > /tmp/t0
      $ echo '#!/tmp/t0' > /tmp/t1
      $ echo '#!/tmp/t1' > /tmp/t2
      $ chmod +x /tmp/t*
      $ /tmp/t2
      zsh: exec format error: /tmp/t2
      Similar problem with binfmt_misc.
      This patch introduces field 'recursion_depth' into struct linux_binprm to
      track recursion level in binfmt_misc and binfmt_script.  If recursion
      level more then BINPRM_MAX_RECURSION it generates -ENOEXEC.
      [akpm@linux-foundation.org: make linux_binprm.recursion_depth a uint]
      Signed-off-by: 's avatarKirill A. Shutemov <kirill@shutemov.name>
      Cc: Pavel Emelyanov <xemul@openvz.org>
      Cc: Alexander Viro <viro@zeniv.linux.org.uk>
      Signed-off-by: 's avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
  10. 29 Apr, 2008 1 commit
    • Pavel Emelyanov's avatar
      binfmt_misc.c: avoid potential kernel stack overflow · 3a2e7f47
      Pavel Emelyanov authored
      This can be triggered with root help only, but...
      Register the ":text:E::txt::/root/cat.txt:' rule in binfmt_misc (by root) and
      try launching the cat.txt file (by anyone) :) The result is - the endless
      recursion in the load_misc_binary -> open_exec -> load_misc_binary chain and
      stack overflow.
      There's a similar problem with binfmt_script, and there's a sh_bang memner on
      linux_binprm structure to handle this, but simply raising this in binfmt_misc
      may break some setups when the interpreter of some misc binaries is a script.
      So the proposal is to turn sh_bang into a bit, add a new one (the misc_bang)
      and raise it in load_misc_binary.  After this, even if we set up the misc ->
      script -> misc loop for binfmts one of them will step on its own bang and
      Signed-off-by: 's avatarPavel Emelyanov <xemul@openvz.org>
      Signed-off-by: 's avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
  11. 19 Oct, 2007 1 commit
  12. 19 Jul, 2007 1 commit
  13. 08 May, 2007 1 commit
  14. 16 Apr, 2005 1 commit
    • Linus Torvalds's avatar
      Linux-2.6.12-rc2 · 1da177e4
      Linus Torvalds authored
      Initial git repository build. I'm not bothering with the full history,
      even though we have it. We can create a separate "historical" git
      archive of that later if we want to, and in the meantime it's about
      3.2GB when imported into git - space that would just make the early
      git days unnecessarily complicated, when we don't have a lot of good
      infrastructure for it.
      Let it rip!