[ Upstream commit 8892d8545f2d0342b9c550defbfb165db237044b ]

Changing protection is a very high cost operation in UML
because in addition to an extra syscall it also interrupts
mmap merge sequences generated by the tlb.

While the condition is not particularly common it is worth
avoiding.

Signed-off-by: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Sasha Levin <sashal@kernel.org>

[ Upstream commit 7ff1e34bbdc15acab823b1ee4240e94623d50ee8 ]

Fixes:
arch/um/os-Linux/skas/process.c:613:1: warning: control reaches end of
non-void function [-Wreturn-type]

longjmp() never returns but gcc still warns that the end of the function
can be reached.
Add a return code and debug aid to detect this impossible case.

Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Sasha Levin <sashal@kernel.org>

[ Upstream commit f44f1e7da7c8e3f4575d5d61c4df978496903fcc ]

Building a statically linked UML kernel on a Centos 6.9 host resulted in
the following linking failure (GCC 4.4, glibc-2.12):

/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../lib64/libpthread.a(libpthread.o):
In function `siglongjmp':
(.text+0x8490): multiple definition of `longjmp'
arch/x86/um/built-in.o:/local/users/fainelli/openwrt/trunk/build_dir/target-x86_64_musl/linux-uml/linux-4.4.69/arch/x86/um/setjmp_64.S:44:
first defined here
/usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../lib64/libpthread.a(libpthread.o):
In function `sem_open':
(.text+0x77cd): warning: the use of `mktemp' is dangerous, better use
`mkstemp'
collect2: ld returned 1 exit status
make[4]: *** [vmlinux] Error 1

Adopt a solution similar to the one done for vmap where we define
longjmp/setjmp to be kernel_longjmp/setjmp. In the process, make sure we
do rename the functions in arch/x86/um/setjmp_*.S accordingly.

Fixes: a7df4716d195 ("um: link with -lpthread")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Sasha Levin <sashal@kernel.org>

commit 4d1a535b8ec5e74b42dfd9dc809142653b2597f6 upstream.

glibc 2.26 removed the 'struct ucontext' to "improve" POSIX compliance
and break programs, including User Mode Linux. Fix User Mode Linux
by using POSIX ucontext_t.

This fixes:

arch/um/os-Linux/signal.c: In function 'hard_handler':
arch/um/os-Linux/signal.c:163:22: error: dereferencing pointer to incomplete type 'struct ucontext'
  mcontext_t *mc = &uc->uc_mcontext;
arch/x86/um/stub_segv.c: In function 'stub_segv_handler':
arch/x86/um/stub_segv.c:16:13: error: dereferencing pointer to incomplete type 'struct ucontext'
          &uc->uc_mcontext);

Cc: stable@vger.kernel.org
Signed-off-by: Krzysztof Mazur <krzysiek@podlesie.net>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 883354afbc109c57f925ccc19840055193da0cc0 upstream.

Debian's gcc defaults to pie. The global Makefile already defines the -fno-pie option.
Link UML dynamic kernel image also with -no-pie to fix the build.

Signed-off-by: Thomas Meyer <thomas@m3y3r.de>
Signed-off-by: Richard Weinberger <richard@nod.at>
Cc: Bernie Innocenti <codewiz@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit dad2232844073295c64e9cc2d734a0ade043e0f6 upstream.

Commit e41f501d3912 ("vmlinux.lds: account for destructor sections")
added '.text.exit' to EXIT_TEXT which is discarded at link time by default.
This breaks compilation of UML:
     `.text.exit' referenced in section `.fini_array' of
     /usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/libc.a(sdlerror.o):
     defined in discarded section `.text.exit' of
     /usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/libc.a(sdlerror.o)

Apparently UML doesn't want to discard exit text, so let's place all EXIT_TEXT
sections in .exit.text.

Fixes: e41f501d3912 ("vmlinux.lds: account for destructor sections")
Reported-by: Stefan Traby <stefan@hello-penguin.com>
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 378c6520e7d29280f400ef2ceaf155c86f05a71a upstream.

This commit fixes the following security hole affecting systems where
all of the following conditions are fulfilled:

 - The fs.suid_dumpable sysctl is set to 2.
 - The kernel.core_pattern sysctl's value starts with "/". (Systems
   where kernel.core_pattern starts with "|/" are not affected.)
 - Unprivileged user namespace creation is permitted. (This is
   true on Linux >=3.8, but some distributions disallow it by
   default using a distro patch.)

Under these conditions, if a program executes under secure exec rules,
causing it to run with the SUID_DUMP_ROOT flag, then unshares its user
namespace, changes its root directory and crashes, the coredump will be
written using fsuid=0 and a path derived from kernel.core_pattern - but
this path is interpreted relative to the root directory of the process,
allowing the attacker to control where a coredump will be written with
root privileges.

To fix the security issue, always interpret core_pattern for dumps that
are written under SUID_DUMP_ROOT relative to the root directory of init.

Signed-off-by: Jann Horn <jann@thejh.net>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 0754fb298f2f2719f0393491d010d46cfb25d043 upstream.

I was seeing some really weird behaviour where piping UML's output
somewhere would cause output to get duplicated:

  $ ./vmlinux | head -n 40
  Checking that ptrace can change system call numbers...Core dump limits :
          soft - 0
          hard - NONE
  OK
  Checking syscall emulation patch for ptrace...Core dump limits :
          soft - 0
          hard - NONE
  OK
  Checking advanced syscall emulation patch for ptrace...Core dump limits :
          soft - 0
          hard - NONE
  OK
  Core dump limits :
          soft - 0
          hard - NONE

This is because these tests do a fork() which duplicates the non-empty
stdout buffer, then glibc flushes the duplicated buffer as each child
exits.

A simple workaround is to flush before forking.

Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

When using va_list ensure that va_start will be followed by va_end.

Signed-off-by: Geyslan G. Bem <geyslan@gmail.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

On gcc Ubuntu 4.8.4-2ubuntu1~14.04, linking vmlinux fails with:

arch/um/os-Linux/built-in.o: In function `os_timer_create':
/android/kernel/android/arch/um/os-Linux/time.c:51: undefined reference to `timer_create'
arch/um/os-Linux/built-in.o: In function `os_timer_set_interval':
/android/kernel/android/arch/um/os-Linux/time.c:84: undefined reference to `timer_settime'
arch/um/os-Linux/built-in.o: In function `os_timer_remain':
/android/kernel/android/arch/um/os-Linux/time.c:109: undefined reference to `timer_gettime'
arch/um/os-Linux/built-in.o: In function `os_timer_one_shot':
/android/kernel/android/arch/um/os-Linux/time.c:132: undefined reference to `timer_settime'
arch/um/os-Linux/built-in.o: In function `os_timer_disable':
/android/kernel/android/arch/um/os-Linux/time.c:145: undefined reference to `timer_settime'

This is because -lrt appears in the generated link commandline
after arch/um/os-Linux/built-in.o. Fix this by removing -lrt from
arch/um/Makefile and adding it to the UM-specific section of
scripts/link-vmlinux.sh.

Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: Richard Weinberger <richard@nod.at>