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    Subject[PATCH AUTOSEL for 4.9 289/293] vfs/proc/kcore, x86/mm/kcore: Fix SMAP fault when dumping vsyscall user page
    Date
    From: Jia Zhang <zhang.jia@linux.alibaba.com>

    [ Upstream commit 595dd46ebfc10be041a365d0a3fa99df50b6ba73 ]

    Commit:

    df04abfd181a ("fs/proc/kcore.c: Add bounce buffer for ktext data")

    ... introduced a bounce buffer to work around CONFIG_HARDENED_USERCOPY=y.
    However, accessing the vsyscall user page will cause an SMAP fault.

    Replace memcpy() with copy_from_user() to fix this bug works, but adding
    a common way to handle this sort of user page may be useful for future.

    Currently, only vsyscall page requires KCORE_USER.

    Signed-off-by: Jia Zhang <zhang.jia@linux.alibaba.com>
    Reviewed-by: Jiri Olsa <jolsa@kernel.org>
    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: jolsa@redhat.com
    Link: http://lkml.kernel.org/r/1518446694-21124-2-git-send-email-zhang.jia@linux.alibaba.com
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    ---
    arch/x86/mm/init_64.c | 3 +--
    fs/proc/kcore.c | 4 ++++
    include/linux/kcore.h | 1 +
    3 files changed, 6 insertions(+), 2 deletions(-)

    diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
    index 7df8e3a79dc0..d35d0e4bbf99 100644
    --- a/arch/x86/mm/init_64.c
    +++ b/arch/x86/mm/init_64.c
    @@ -1014,8 +1014,7 @@ void __init mem_init(void)
    after_bootmem = 1;

    /* Register memory areas for /proc/kcore */
    - kclist_add(&kcore_vsyscall, (void *)VSYSCALL_ADDR,
    - PAGE_SIZE, KCORE_OTHER);
    + kclist_add(&kcore_vsyscall, (void *)VSYSCALL_ADDR, PAGE_SIZE, KCORE_USER);

    mem_init_print_info(NULL);
    }
    diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
    index df7e07986ead..7ed961c0124f 100644
    --- a/fs/proc/kcore.c
    +++ b/fs/proc/kcore.c
    @@ -505,6 +505,10 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
    /* we have to zero-fill user buffer even if no read */
    if (copy_to_user(buffer, buf, tsz))
    return -EFAULT;
    + } else if (m->type == KCORE_USER) {
    + /* User page is handled prior to normal kernel page: */
    + if (copy_to_user(buffer, (char *)start, tsz))
    + return -EFAULT;
    } else {
    if (kern_addr_valid(start)) {
    /*
    diff --git a/include/linux/kcore.h b/include/linux/kcore.h
    index d92762286645..3ffade4f2798 100644
    --- a/include/linux/kcore.h
    +++ b/include/linux/kcore.h
    @@ -9,6 +9,7 @@ enum kcore_type {
    KCORE_VMALLOC,
    KCORE_RAM,
    KCORE_VMEMMAP,
    + KCORE_USER,
    KCORE_OTHER,
    };

    --
    2.15.1
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