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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
c3350602e8 ("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: c3350602e8 ("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
Makefile powerpc updates for 4.15 2017-11-16 12:47:46 -08:00
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-common.c Merge branch 'topic/ppc-kvm' into next 2017-02-14 17:18:29 +11:00
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
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.c cxl: Enable global TLBIs for cxl contexts 2017-09-28 17:09:16 +10:00
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_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-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
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
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.c powerpc/64s: Rename slb_allocate_realmode() to slb_allocate() 2017-06-21 16:18:33 +10:00
slb_low.S powerpc/64s: mm_context.addr_limit is only used on hash 2017-11-13 23:35:43 +11:00
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-radix.c powerpc/64s/radix: Improve TLB flushing for page table freeing 2017-11-10 21:33:35 +11:00
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.c powerpc/nohash: Fix use of mmu_has_feature() in setup_initial_memory_limit() 2017-04-11 07:46:04 +10:00
tlb_nohash_low.S powerpc/8xx: Getting rid of remaining use of CONFIG_8xx 2017-08-10 23:32:12 +10:00
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