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    Subject[PATCH 3.10 203/250] metag/usercopy: Add early abort to copy_to_user
    Date
    From: James Hogan <james.hogan@imgtec.com>

    commit fb8ea062a8f2e85256e13f55696c5c5f0dfdcc8b upstream.

    When copying to userland on Meta, if any faults are encountered
    immediately abort the copy instead of continuing on and repeatedly
    faulting, and worse potentially copying further bytes successfully to
    subsequent valid pages.

    Fixes: 373cd784d0fc ("metag: Memory handling")
    Reported-by: Al Viro <viro@zeniv.linux.org.uk>
    Signed-off-by: James Hogan <james.hogan@imgtec.com>
    Cc: linux-metag@vger.kernel.org
    Signed-off-by: Jiri Slaby <jslaby@suse.cz>
    Signed-off-by: Willy Tarreau <w@1wt.eu>
    ---
    arch/metag/lib/usercopy.c | 20 ++++++++++++++++++++
    1 file changed, 20 insertions(+)

    diff --git a/arch/metag/lib/usercopy.c b/arch/metag/lib/usercopy.c
    index a26c889..212c99a 100644
    --- a/arch/metag/lib/usercopy.c
    +++ b/arch/metag/lib/usercopy.c
    @@ -538,23 +538,31 @@ unsigned long __copy_user(void __user *pdst, const void *psrc,
    if ((unsigned long) src & 1) {
    __asm_copy_to_user_1(dst, src, retn);
    n--;
    + if (retn)
    + return retn + n;
    }
    if ((unsigned long) dst & 1) {
    /* Worst case - byte copy */
    while (n > 0) {
    __asm_copy_to_user_1(dst, src, retn);
    n--;
    + if (retn)
    + return retn + n;
    }
    }
    if (((unsigned long) src & 2) && n >= 2) {
    __asm_copy_to_user_2(dst, src, retn);
    n -= 2;
    + if (retn)
    + return retn + n;
    }
    if ((unsigned long) dst & 2) {
    /* Second worst case - word copy */
    while (n >= 2) {
    __asm_copy_to_user_2(dst, src, retn);
    n -= 2;
    + if (retn)
    + return retn + n;
    }
    }

    @@ -569,6 +577,8 @@ unsigned long __copy_user(void __user *pdst, const void *psrc,
    while (n >= 8) {
    __asm_copy_to_user_8x64(dst, src, retn);
    n -= 8;
    + if (retn)
    + return retn + n;
    }
    }
    if (n >= RAPF_MIN_BUF_SIZE) {
    @@ -581,6 +591,8 @@ unsigned long __copy_user(void __user *pdst, const void *psrc,
    while (n >= 8) {
    __asm_copy_to_user_8x64(dst, src, retn);
    n -= 8;
    + if (retn)
    + return retn + n;
    }
    }
    #endif
    @@ -588,11 +600,15 @@ unsigned long __copy_user(void __user *pdst, const void *psrc,
    while (n >= 16) {
    __asm_copy_to_user_16(dst, src, retn);
    n -= 16;
    + if (retn)
    + return retn + n;
    }

    while (n >= 4) {
    __asm_copy_to_user_4(dst, src, retn);
    n -= 4;
    + if (retn)
    + return retn + n;
    }

    switch (n) {
    @@ -609,6 +625,10 @@ unsigned long __copy_user(void __user *pdst, const void *psrc,
    break;
    }

    + /*
    + * If we get here, retn correctly reflects the number of failing
    + * bytes.
    + */
    return retn;
    }
    EXPORT_SYMBOL(__copy_user);
    --
    2.8.0.rc2.1.gbe9624a
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