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    Subject[PATCH v2 43/44] x86/unwind: warn on bad stack return address
    Date
    If __kernel_text_address() doesn't recognize a return address on the
    stack, it probably means that it's some generated code which
    __kernel_text_address() doesn't know about yet.

    Otherwise there's probably some stack corruption.

    Either way, warn about it.

    Use printk_deferred_once() because the unwinder can be called with the
    console lock by lockdep via save_stack_trace().

    Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
    ---
    arch/x86/kernel/unwind_frame.c | 8 +++++++-
    1 file changed, 7 insertions(+), 1 deletion(-)

    diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
    index d90c2c9..f943413 100644
    --- a/arch/x86/kernel/unwind_frame.c
    +++ b/arch/x86/kernel/unwind_frame.c
    @@ -17,7 +17,13 @@ unsigned long unwind_get_return_address(struct unwind_state *state)
    addr = ftrace_graph_ret_addr(state->task, &state->graph_idx, *addr_p,
    addr_p);

    - return __kernel_text_address(addr) ? addr : 0;
    + if (!__kernel_text_address(addr)) {
    + printk_deferred_once(KERN_WARNING "WARNING: unrecognized kernel stack return address %p in %s:%d\n",
    + (void *)addr, state->task->comm, state->task->pid);
    + return 0;
    + }
    +
    + return addr;
    }
    EXPORT_SYMBOL_GPL(unwind_get_return_address);

    --
    2.7.4
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