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    Subject[PATCH 4.16 106/279] arm64: fix possible spectre-v1 in ptrace_hbp_get_event()
    Date
    4.16-stable review patch.  If anyone has any objections, please let me know.

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

    From: Mark Rutland <mark.rutland@arm.com>

    [ Upstream commit 19791a7ca674fb3009bb068260e852a2f05b605c ]

    It's possible for userspace to control idx. Sanitize idx when using it
    as an array index.

    Found by smatch.

    Signed-off-by: Mark Rutland <mark.rutland@arm.com>
    Cc: Catalin Marinas <catalin.marinas@arm.com>
    Cc: Will Deacon <will.deacon@arm.com>
    Signed-off-by: Will Deacon <will.deacon@arm.com>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/arm64/kernel/ptrace.c | 14 ++++++++++----
    1 file changed, 10 insertions(+), 4 deletions(-)

    --- a/arch/arm64/kernel/ptrace.c
    +++ b/arch/arm64/kernel/ptrace.c
    @@ -25,6 +25,7 @@
    #include <linux/sched/signal.h>
    #include <linux/sched/task_stack.h>
    #include <linux/mm.h>
    +#include <linux/nospec.h>
    #include <linux/smp.h>
    #include <linux/ptrace.h>
    #include <linux/user.h>
    @@ -249,15 +250,20 @@ static struct perf_event *ptrace_hbp_get

    switch (note_type) {
    case NT_ARM_HW_BREAK:
    - if (idx < ARM_MAX_BRP)
    - bp = tsk->thread.debug.hbp_break[idx];
    + if (idx >= ARM_MAX_BRP)
    + goto out;
    + idx = array_index_nospec(idx, ARM_MAX_BRP);
    + bp = tsk->thread.debug.hbp_break[idx];
    break;
    case NT_ARM_HW_WATCH:
    - if (idx < ARM_MAX_WRP)
    - bp = tsk->thread.debug.hbp_watch[idx];
    + if (idx >= ARM_MAX_WRP)
    + goto out;
    + idx = array_index_nospec(idx, ARM_MAX_WRP);
    + bp = tsk->thread.debug.hbp_watch[idx];
    break;
    }

    +out:
    return bp;
    }


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