John Sperbeck ecb101aed8 powerpc/mm: Fix SEGV on mapped region to return SEGV_ACCERR ...

The recent refactoring of the powerpc page fault handler in commit
c3350602e876 ("powerpc/mm: Make bad_area* helper functions") caused
access to protected memory regions to indicate SEGV_MAPERR instead of
the traditional SEGV_ACCERR in the si_code field of a user-space
signal handler. This can confuse debug libraries that temporarily
change the protection of memory regions, and expect to use SEGV_ACCERR
as an indication to restore access to a region.

This commit restores the previous behavior. The following program
exhibits the issue:

    $ ./repro read  || echo "FAILED"
    $ ./repro write || echo "FAILED"
    $ ./repro exec  || echo "FAILED"

    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <unistd.h>
    #include <signal.h>
    #include <sys/mman.h>
    #include <assert.h>

    static void segv_handler(int n, siginfo_t *info, void *arg) {
            _exit(info->si_code == SEGV_ACCERR ? 0 : 1);
    }

    int main(int argc, char **argv)
    {
            void *p = NULL;
            struct sigaction act = {
                    .sa_sigaction = segv_handler,
                    .sa_flags = SA_SIGINFO,
            };

            assert(argc == 2);
            p = mmap(NULL, getpagesize(),
                    (strcmp(argv[1], "write") == 0) ? PROT_READ : 0,
                    MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
            assert(p != MAP_FAILED);

            assert(sigaction(SIGSEGV, &act, NULL) == 0);
            if (strcmp(argv[1], "read") == 0)
                    printf("%c", *(unsigned char *)p);
            else if (strcmp(argv[1], "write") == 0)
                    *(unsigned char *)p = 0;
            else if (strcmp(argv[1], "exec") == 0)
                    ((void (*)(void))p)();
            return 1;  /* failed to generate SEGV */
    }

Fixes: c3350602e876 ("powerpc/mm: Make bad_area* helper functions")
Cc: stable@vger.kernel.org # v4.14+
Signed-off-by: John Sperbeck <jsperbeck@google.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
[mpe: Add commit references in change log]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

2018-01-02 21:12:33 +11:00

..

8xx_mmu.c

powerpc/8xx: mark init functions with __init

2017-08-15 22:55:54 +10:00

40x_mmu.c

Replace <asm/uaccess.h> with <linux/uaccess.h> globally

2016-12-24 11:46:01 -08:00

44x_mmu.c

powerpc: Delete __cpuinit usage from all users

2013-07-01 11:10:36 +10:00

copro_fault.c

powerpc/mm: Update PROTFAULT handling in the page fault path

2017-02-15 20:02:39 +11:00

dma-noncoherent.c

powerpc/mm: Rename map_page() to map_kernel_page() on 32-bit

2017-06-05 19:59:03 +10:00

dump_hashpagetable.c

powerpc/64s: Replace CONFIG_PPC_STD_MMU_64 with CONFIG_PPC_BOOK3S_64

2017-11-06 16:48:14 +11:00

dump_linuxpagetables.c

powerpc/64s: Replace CONFIG_PPC_STD_MMU_64 with CONFIG_PPC_BOOK3S_64

2017-11-06 16:48:14 +11:00

fault.c

powerpc/mm: Fix SEGV on mapped region to return SEGV_ACCERR

2018-01-02 21:12:33 +11:00

fsl_booke_mmu.c

Replace <asm/uaccess.h> with <linux/uaccess.h> globally

2016-12-24 11:46:01 -08:00

hash64_4k.c

powerpc/mm: Fix lazy icache flush on pre-POWER5

2016-11-29 23:59:40 +11:00

hash64_64k.c

powerpc/mm: Fix lazy icache flush on pre-POWER5

2016-11-29 23:59:40 +11:00

hash_low_32.S

powerpc: fix location of two EXPORT_SYMBOL

2017-09-01 16:42:45 +10:00

hash_native_64.c

powerpc/powernv: Fix kexec crashes caused by tlbie tracing

2017-11-23 23:10:14 +11:00

hash_utils_64.c

powerpc/mm/hash: Add pr_fmt() to hash_utils64.c

2017-11-06 16:48:13 +11:00

highmem.c

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

2017-11-02 11:10:55 +01:00

hugepage-hash64.c

powerpc/mm: Move hash table ops to a separate structure

2016-07-21 18:59:09 +10:00

hugetlbpage-book3e.c

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

2017-11-02 11:10:55 +01:00

hugetlbpage-hash64.c

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

2017-11-02 11:10:55 +01:00

hugetlbpage-radix.c

powerpc updates for 4.15

2017-11-16 12:47:46 -08:00

hugetlbpage.c

mm: account pud page tables

2017-11-15 18:21:04 -08:00

init_32.c

powerpc/mm/hugetlb: Add support for reserving gigantic huge pages via kernel command line

2017-08-16 14:56:12 +10:00

init_64.c

powerpc/mm: Add a CONFIG option to choose if radix is used by default

2017-11-06 16:48:15 +11:00

init-common.c

Merge branch 'topic/ppc-kvm' into next

2017-02-14 17:18:29 +11:00

Makefile

powerpc updates for 4.15

2017-11-16 12:47:46 -08:00

mem.c

powerpc/8xx: Getting rid of remaining use of CONFIG_8xx

2017-08-10 23:32:12 +10:00

mmap.c

powerpc/64s: mm_context.addr_limit is only used on hash

2017-11-13 23:35:43 +11:00

mmu_context_book3s64.c

powerpc updates for 4.15

2017-11-16 12:47:46 -08:00

mmu_context_hash32.c

powerpc: Remove power3 from comments

2014-07-28 14:10:26 +10:00

mmu_context_iommu.c

Merge branch 'topic/ppc-kvm' into next

2017-04-28 20:19:37 +10:00

mmu_context_nohash.c

powerpc/mm/nohash: MM_SLICE is only used by book3s 64

2017-03-31 23:09:47 +11:00

mmu_context.c

cxl: Enable global TLBIs for cxl contexts

2017-09-28 17:09:16 +10:00

mmu_decl.h

powerpc/8xx: Getting rid of remaining use of CONFIG_8xx

2017-08-10 23:32:12 +10:00

numa.c

powerpc updates for 4.15

2017-11-16 12:47:46 -08:00

pgtable_32.c

powerpc/mm: Call flush_tlb_kernel_range with interrupts enabled

2017-10-04 22:15:30 +11:00

pgtable_64.c

powerpc updates for 4.15

2017-11-16 12:47:46 -08:00

pgtable-book3e.c

powerpc/mm: Make page table size a variable

2016-05-01 18:32:48 +10:00

pgtable-book3s64.c

powerpc/mm/cxl: Add the fault handling cpu to mm cpumask

2017-08-17 23:31:52 +10:00

pgtable-hash64.c

powerpc/mm: Use mm_is_thread_local() instread of open-coding

2017-08-23 22:27:45 +10:00

pgtable-radix.c

powerpc/mm/radix: Fix crashes on Power9 DD1 with radix MMU and STRICT_RWX

2017-11-12 23:25:48 +11:00

pgtable.c

powerpc/mm: Fix typo in set_pte_at()

2017-02-17 22:16:25 +11:00

ppc_mmu_32.c

powerpc32: refactor x_mapped_by_bats() and x_mapped_by_tlbcam() together

2016-03-11 17:18:02 -06:00

slb_low.S

powerpc/64s: mm_context.addr_limit is only used on hash

2017-11-13 23:35:43 +11:00

slb.c

powerpc/64s: Rename slb_allocate_realmode() to slb_allocate()

2017-06-21 16:18:33 +10:00

slice.c

powerpc/64s/slice: Use addr limit when computing slice mask

2017-11-20 19:28:25 +11:00

subpage-prot.c

powerpc/mm/hash: Free the subpage_prot_table correctly

2017-07-27 13:05:50 +10:00

tlb_hash32.c

powerpc/mm: remove flush_tlb_page_nohash

2016-08-01 11:15:13 +10:00

tlb_hash64.c

powerpc/mm: Use mm_is_thread_local() instread of open-coding

2017-08-23 22:27:45 +10:00

tlb_low_64e.S

powerpc: Fix misspellings in comments.

2016-03-01 19:27:20 +11:00

tlb_nohash_low.S

powerpc/8xx: Getting rid of remaining use of CONFIG_8xx

2017-08-10 23:32:12 +10:00

tlb_nohash.c

powerpc/nohash: Fix use of mmu_has_feature() in setup_initial_memory_limit()

2017-04-11 07:46:04 +10:00

tlb-radix.c

powerpc/64s/radix: Improve TLB flushing for page table freeing

2017-11-10 21:33:35 +11:00

vphn.c

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

2017-11-02 11:10:55 +01:00

vphn.h

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

2017-11-02 11:10:55 +01:00