• Zhou Chengming's avatar
    kprobes, x86/alternatives: Use text_mutex to protect smp_alt_modules · e846d139
    Zhou Chengming authored
    We use alternatives_text_reserved() to check if the address is in
    the fixed pieces of alternative reserved, but the problem is that
    we don't hold the smp_alt mutex when call this function. So the list
    traversal may encounter a deleted list_head if another path is doing
    One solution is that we can hold smp_alt mutex before call this
    function, but the difficult point is that the callers of this
    functions, arch_prepare_kprobe() and arch_prepare_optimized_kprobe(),
    are called inside the text_mutex. So we must hold smp_alt mutex
    before we go into these arch dependent code. But we can't now,
    the smp_alt mutex is the arch dependent part, only x86 has it.
    Maybe we can export another arch dependent callback to solve this.
    But there is a simpler way to handle this problem. We can reuse the
    text_mutex to protect smp_alt_modules instead of using another mutex.
    And all the arch dependent checks of kprobes are inside the text_mutex,
    so it's safe now.
    Signed-off-by: default avatarZhou Chengming <zhouchengming1@huawei.com>
    Reviewed-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
    Acked-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Brian Gerst <brgerst@gmail.com>
    Cc: Denys Vlasenko <dvlasenk@redhat.com>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Josh Poimboeuf <jpoimboe@redhat.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: bp@suse.de
    Fixes: 2cfa1978 "ftrace/alternatives: Introducing *_text_reserved functions"
    Link: http://lkml.kernel.org/r/1509585501-79466-1-git-send-email-zhouchengming1@huawei.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
extable.c 4.8 KB