4.4.153-stable review

4.4-stable review patch. If anyone has any objections, please let me know.

------------------

From: Andi Kleen <[email protected]>

Patch for stable only to fix boot resets caused by the L1TF patches.

Stable trees reverted the following patch

Revert "x86/mm/pat: Ensure cpa->pfn only contains page frame numbers"

    This reverts commit 87e2bd898d3a79a8c609f183180adac47879a2a4 which is
    commit edc3b9129cecd0f0857112136f5b8b1bc1d45918 upstream.

but the L1TF patch backported here

x86/mm/pat: Make set_memory_np() L1TF safe

commit 958f79b9ee55dfaf00c8106ed1c22a2919e0028b upstream

set_memory_np() is used to mark kernel mappings not present, but it has it's own open coded mechanism which does not have the L1TF protection of inverting the address bits.

assumed that cpa->pfn contains a PFN. With the above patch reverted it does not, which causes the PMD to be set to an incorrect address shifted by 12 bits, which can cause early boot reset on some systems, like an Apollo Lake embedded system.

Convert the address to a PFN before passing it to pmd_pfn()

Thanks to Bernhard for bisecting and testing.

---
 arch/x86/mm/pageattr.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -1006,7 +1006,7 @@ static int populate_pmd(struct cpa_data
 
 		pmd = pmd_offset(pud, start);
 
-		set_pmd(pmd, pmd_mkhuge(pfn_pmd(cpa->pfn,
+		set_pmd(pmd, pmd_mkhuge(pfn_pmd(cpa->pfn >> PAGE_SHIFT,
 					canon_pgprot(pmd_pgprot))));
 
 		start	  += PMD_SIZE;

4.4-stable review patch. If anyone has any objections, please let me know.

------------------

From: Eric Biggers <[email protected]>

commit ccd5b3235180eef3cfec337df1c8554ab151b5cc upstream.

The following commit:

39a0526fb3f7 ("x86/mm: Factor out LDT init from context init")

renamed init_new_context() to init_new_context_ldt() and added a new init_new_context() which calls init_new_context_ldt(). However, the error code of init_new_context_ldt() was ignored. Consequently, if a memory allocation in alloc_ldt_struct() failed during a fork(), the ->context.ldt of the new task remained the same as that of the old task (due to the memcpy() in dup_mm()). ldt_struct's are not intended to be shared, so a use-after-free occurred after one task exited.

Fix the bug by making init_new_context() pass through the error code of init_new_context_ldt().

This bug was found by syzkaller, which encountered the following splat:

    BUG: KASAN: use-after-free in free_ldt_struct.part.2+0x10a/0x150 arch/x86/kernel/ldt.c:116
    Read of size 4 at addr ffff88006d2cb7c8 by task kworker/u9:0/3710

    CPU: 1 PID: 3710 Comm: kworker/u9:0 Not tainted 4.13.0-rc4-next-20170811 #2
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
    Call Trace:
     __dump_stack lib/dump_stack.c:16 [inline]
     dump_stack+0x194/0x257 lib/dump_stack.c:52
     print_address_description+0x73/0x250 mm/kasan/report.c:252
     kasan_report_error mm/kasan/report.c:351 [inline]
     kasan_report+0x24e/0x340 mm/kasan/report.c:409
     __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:429
     free_ldt_struct.part.2+0x10a/0x150 arch/x86/kernel/ldt.c:116
     free_ldt_struct arch/x86/kernel/ldt.c:173 [inline]
     destroy_context_ldt+0x60/0x80 arch/x86/kernel/ldt.c:171
     destroy_context arch/x86/include/asm/mmu_context.h:157 [inline]
     __mmdrop+0xe9/0x530 kernel/fork.c:889
     mmdrop include/linux/sched/mm.h:42 [inline]
     exec_mmap fs/exec.c:1061 [inline]
     flush_old_exec+0x173c/0x1ff0 fs/exec.c:1291
     load_elf_binary+0x81f/0x4ba0 fs/binfmt_elf.c:855
     search_binary_handler+0x142/0x6b0 fs/exec.c:1652
     exec_binprm fs/exec.c:1694 [inline]
     do_execveat_common.isra.33+0x1746/0x22e0 fs/exec.c:1816
     do_execve+0x31/0x40 fs/exec.c:1860
     call_usermodehelper_exec_async+0x457/0x8f0 kernel/umh.c:100
     ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431

    Allocated by task 3700:
     save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
     save_stack+0x43/0xd0 mm/kasan/kasan.c:447
     set_track mm/kasan/kasan.c:459 [inline]
     kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
     kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3627
     kmalloc include/linux/slab.h:493 [inline]
     alloc_ldt_struct+0x52/0x140 arch/x86/kernel/ldt.c:67
     write_ldt+0x7b7/0xab0 arch/x86/kernel/ldt.c:277
     sys_modify_ldt+0x1ef/0x240 arch/x86/kernel/ldt.c:307
     entry_SYSCALL_64_fastpath+0x1f/0xbe

    Freed by task 3700:
     save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
     save_stack+0x43/0xd0 mm/kasan/kasan.c:447
     set_track mm/kasan/kasan.c:459 [inline]
     kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
     __cache_free mm/slab.c:3503 [inline]
     kfree+0xca/0x250 mm/slab.c:3820
     free_ldt_struct.part.2+0xdd/0x150 arch/x86/kernel/ldt.c:121
     free_ldt_struct arch/x86/kernel/ldt.c:173 [inline]
     destroy_context_ldt+0x60/0x80 arch/x86/kernel/ldt.c:171
     destroy_context arch/x86/include/asm/mmu_context.h:157 [inline]
     __mmdrop+0xe9/0x530 kernel/fork.c:889
     mmdrop include/linux/sched/mm.h:42 [inline]
     __mmput kernel/fork.c:916 [inline]
     mmput+0x541/0x6e0 kernel/fork.c:927
     copy_process.part.36+0x22e1/0x4af0 kernel/fork.c:1931
     copy_process kernel/fork.c:1546 [inline]
     _do_fork+0x1ef/0xfb0 kernel/fork.c:2025
     SYSC_clone kernel/fork.c:2135 [inline]
     SyS_clone+0x37/0x50 kernel/fork.c:2129
     do_syscall_64+0x26c/0x8c0 arch/x86/entry/common.c:287
     return_from_SYSCALL_64+0x0/0x7a

Here is a C reproducer:

    #include <asm/ldt.h>
    #include <pthread.h>
    #include <signal.h>
    #include <stdlib.h>
    #include <sys/syscall.h>
    #include <sys/wait.h>
    #include <unistd.h>

    static void *fork_thread(void *_arg)
    {
        fork();
    }

    int main(void)
    {
        struct user_desc desc = { .entry_number = 8191 };

        syscall(__NR_modify_ldt, 1, &desc, sizeof(desc));

        for (;;) {
            if (fork() == 0) {
                pthread_t t;

                srand(getpid());
                pthread_create(&t, NULL, fork_thread, NULL);
                usleep(rand() % 10000);
                syscall(__NR_exit_group, 0);
            }
            wait(NULL);
        }
    }

Note: the reproducer takes advantage of the fact that alloc_ldt_struct() may use vmalloc() to allocate a large ->entries array, and after commit:

5d17a73a2ebe ("vmalloc: back off when the current task is killed")

it is possible for userspace to fail a task's vmalloc() by sending a fatal signal, e.g. via exit_group(). It would be more difficult to reproduce this bug on kernels without that commit.

This bug only affected kernels with CONFIG_MODIFY_LDT_SYSCALL=y.

---
 arch/x86/include/asm/mmu_context.h |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

@@ -109,8 +109,7 @@ static inline int init_new_context(struc
 				   struct mm_struct *mm)
 {
 	mm->context.ctx_id = atomic64_inc_return(&last_mm_ctx_id);
-	init_new_context_ldt(tsk, mm);
-	return 0;
+	return init_new_context_ldt(tsk, mm);
 }
 static inline void destroy_context(struct mm_struct *mm)
 {

This is the start of the stable review cycle for the 4.4.153 release. There are 5 patches in this series, all will be posted as a response to this one. If anyone has any issues with these being applied, please let me know.

Responses should be made by Tue Aug 28 06:40:50 UTC 2018. Anything received after that time might be too late.

The whole patch series can be found in one patch at:

	https://www.kernel.org/pub/linux/kernel/v4.x/stable-review/patch-4.4.153-rc1.gz

or in the git tree and branch at:
git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-4.4.y
and the diffstat can be found below.

thanks,

greg k-h

-------------
Pseudo-Shortlog of commits:

Greg Kroah-Hartman <[email protected]>

    Linux 4.4.153-rc1

Vivek Goyal <[email protected]>
ovl: warn instead of error if d_type is not supported

Vivek Goyal <[email protected]>
ovl: Do d_type check only if work dir creation was successful

Vivek Goyal <[email protected]>
ovl: Ensure upper filesystem supports d_type

Eric Biggers <[email protected]>
x86/mm: Fix use-after-free of ldt_struct

Andi Kleen <[email protected]>
x86/mm/pat: Fix L1TF stable backport for CPA

-------------

Diffstat:

 Makefile                           |  4 ++--
 arch/x86/include/asm/mmu_context.h |  3 +--
 arch/x86/mm/pageattr.c             |  2 +-
 fs/overlayfs/overlayfs.h           |  1 +
 fs/overlayfs/readdir.c             | 37 +++++++++++++++++++++++++++++++++++++
 fs/overlayfs/super.c               | 20 ++++++++++++++++++++
 6 files changed, 62 insertions(+), 5 deletions(-)

Build results:

	total: 148 pass: 148 fail: 0
Qemu test results:
	total: 269 pass: 269 fail: 0

Details are available at http://kerneltests.org/builders/.

Guenter

Great, thanks for testing and letting me know.

greg k-h

Results from Linaro’s test farm.
No regressions on arm64, arm and x86_64.

Summary
------------------------------------------------------------------------

kernel: 4.4.153-rc1
git repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git
git branch: linux-4.4.y
git commit: 7994d02b246beb4349cf0ae547c0a6461320e6c7
git describe: v4.4.152-6-g7994d02b246b
Test details: https://qa-reports.linaro.org/lkft/linux-stable-rc-4.4-oe/build/v4.4.152-6-g7994d02b246b

No regressions (compared to build v4.4.152)

Ran 12246 total tests in the following environments and test suites.

Environments
--------------
- juno-r2 - arm64
- qemu_arm
- qemu_x86_64
- x15 - arm
- x86_64

Test Suites
-----------
* boot
* kselftest
* libhugetlbfs
* ltp-cap_bounds-tests
* ltp-containers-tests
* ltp-cve-tests
* ltp-fcntl-locktests-tests
* ltp-filecaps-tests
* ltp-fs-tests
* ltp-fs_bind-tests
* ltp-fs_perms_simple-tests
* ltp-fsx-tests
* ltp-hugetlb-tests
* ltp-io-tests
* ltp-ipc-tests
* ltp-math-tests
* ltp-nptl-tests
* ltp-open-posix-tests
* ltp-pty-tests
* ltp-sched-tests
* ltp-securebits-tests
* ltp-syscalls-tests
* ltp-timers-tests
* kselftest-vsyscall-mode-native
* kselftest-vsyscall-mode-none

Summary
------------------------------------------------------------------------

kernel: 4.4.153-rc1
git repo: https://git.linaro.org/lkft/arm64-stable-rc.git
git branch: 4.4.153-rc1-hikey-20180826-270
git commit: 1d9b202cd56188353c13a49bf48f3f97383984ee
git describe: 4.4.153-rc1-hikey-20180826-270
Test details: https://qa-reports.linaro.org/lkft/linaro-hikey-stable-rc-4.4-oe/build/4.4.153-rc1-hikey-20180826-270

No regressions (compared to build 4.4.152-rc1-hikey-20180823-268)

Ran 2724 total tests in the following environments and test suites.

Environments
--------------
- hi6220-hikey - arm64
- qemu_arm64

Test Suites
-----------
* boot
* kselftest
* libhugetlbfs
* ltp-cap_bounds-tests
* ltp-containers-tests
* ltp-cve-tests
* ltp-fcntl-locktests-tests
* ltp-filecaps-tests
* ltp-fs-tests
* ltp-fs_bind-tests
* ltp-fs_perms_simple-tests
* ltp-fsx-tests
* ltp-hugetlb-tests
* ltp-io-tests
* ltp-ipc-tests
* ltp-math-tests
* ltp-nptl-tests
* ltp-pty-tests
* ltp-sched-tests
* ltp-securebits-tests
* ltp-syscalls-tests
* ltp-timers-tests

Linaro LKFT
https://lkft.linaro.org

Thanks for testing and letting me know.

greg k-h

Compiled and booted on my test system. No dmesg regressions.

thanks,
-- Shuah

Thanks for testing both of these and letting me know.

greg k-h