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2014-12-13syscalls: implement execveat() system callDavid Drysdale
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 https://lkml.org/lkml/2006/7/11/474). 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: David 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: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-12-21exec: do not leave bprm->interp on stackKees Cook
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: Kees 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: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-12-18exec: use -ELOOP for max recursion depthKees Cook
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: Kees 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: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-11-29get rid of pt_regs argument of ->load_binary()Al Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-11-29get rid of pt_regs argument of search_binary_handler()Al Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-03-21__register_binfmt() made voidAl Viro
Just don't pass NULL to it - nobody does, anyway. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18Make do_execve() take a const filename pointerDavid Howells
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: David Howells <dhowells@redhat.com> Tested-by: Ralf Baechle <ralf@linux-mips.org> Acked-by: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-03-30include cleanup: Update gfp.h and slab.h includes to prepare for breaking ↵Tejun Heo
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. http://userweb.kernel.org/~tj/misc/slabh-sweep.py 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 file. 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 files. 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 necessary. 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: Tejun Heo <tj@kernel.org> Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
2008-10-16Allow recursion in binfmt_script and binfmt_miscKirill A. Shutemov
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: Kirill A. Shutemov <kirill@shutemov.name> Cc: Pavel Emelyanov <xemul@openvz.org> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-29binfmt_misc.c: avoid potential kernel stack overflowPavel Emelyanov
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 exit. Signed-off-by: Pavel Emelyanov <xemul@openvz.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-19Convert files to UTF-8 and some cleanupsJan Engelhardt
* Convert files to UTF-8. * Also correct some people's names (one example is Eißfeldt, which was found in a source file. Given that the author used an ß at all in a source file indicates that the real name has in fact a 'ß' and not an 'ss', which is commonly used as a substitute for 'ß' when limited to 7bit.) * Correct town names (Goettingen -> Göttingen) * Update Eberhard Mönkeberg's address (http://lkml.org/lkml/2007/1/8/313) Signed-off-by: Jan Engelhardt <jengelh@gmx.de> Signed-off-by: Adrian Bunk <bunk@kernel.org>
2007-07-19mm: variable length argument supportOllie Wild
Remove the arg+env limit of MAX_ARG_PAGES by copying the strings directly from the old mm into the new mm. We create the new mm before the binfmt code runs, and place the new stack at the very top of the address space. Once the binfmt code runs and figures out where the stack should be, we move it downwards. It is a bit peculiar in that we have one task with two mm's, one of which is inactive. [a.p.zijlstra@chello.nl: limit stack size] Signed-off-by: Ollie Wild <aaw@google.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: <linux-arch@vger.kernel.org> Cc: Hugh Dickins <hugh@veritas.com> [bunk@stusta.de: unexport bprm_mm_init] Signed-off-by: Adrian Bunk <bunk@stusta.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-08header cleaning: don't include smp_lock.h when not usedRandy Dunlap
Remove includes of <linux/smp_lock.h> where it is not used/needed. Suggested by Al Viro. Builds cleanly on x86_64, i386, alpha, ia64, powerpc, sparc, sparc64, and arm (all 59 defconfigs). Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2005-04-16Linux-2.6.12-rc2Linus Torvalds
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!