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    Subject[PATCH 5.12 280/292] jump_label: Fix jump_label_text_reserved() vs __init
    Date
    From: Peter Zijlstra <peterz@infradead.org>

    [ Upstream commit 9e667624c291753b8a5128f620f493d0b5226063 ]

    It turns out that jump_label_text_reserved() was reporting __init text
    as being reserved past the time when the __init text was freed and
    re-used.

    For a long time, this resulted in, at worst, not being able to kprobe
    text that happened to land at the re-used address. However a recent
    commit e7bf1ba97afd ("jump_label, x86: Emit short JMP") made it a
    fatal mistake because it now needs to read the instruction in order to
    determine the conflict -- an instruction that's no longer there.

    Fixes: 4c3ef6d79328 ("jump label: Add jump_label_text_reserved() to reserve jump points")
    Reported-by: kernel test robot <oliver.sang@intel.com>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
    Link: https://lore.kernel.org/r/20210628113045.045141693@infradead.org
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    kernel/jump_label.c | 13 ++++++++-----
    1 file changed, 8 insertions(+), 5 deletions(-)

    diff --git a/kernel/jump_label.c b/kernel/jump_label.c
    index ba39fbb1f8e7..af520ca26360 100644
    --- a/kernel/jump_label.c
    +++ b/kernel/jump_label.c
    @@ -316,14 +316,16 @@ static int addr_conflict(struct jump_entry *entry, void *start, void *end)
    }

    static int __jump_label_text_reserved(struct jump_entry *iter_start,
    - struct jump_entry *iter_stop, void *start, void *end)
    + struct jump_entry *iter_stop, void *start, void *end, bool init)
    {
    struct jump_entry *iter;

    iter = iter_start;
    while (iter < iter_stop) {
    - if (addr_conflict(iter, start, end))
    - return 1;
    + if (init || !jump_entry_is_init(iter)) {
    + if (addr_conflict(iter, start, end))
    + return 1;
    + }
    iter++;
    }

    @@ -561,7 +563,7 @@ static int __jump_label_mod_text_reserved(void *start, void *end)

    ret = __jump_label_text_reserved(mod->jump_entries,
    mod->jump_entries + mod->num_jump_entries,
    - start, end);
    + start, end, mod->state == MODULE_STATE_COMING);

    module_put(mod);

    @@ -786,8 +788,9 @@ early_initcall(jump_label_init_module);
    */
    int jump_label_text_reserved(void *start, void *end)
    {
    + bool init = system_state < SYSTEM_RUNNING;
    int ret = __jump_label_text_reserved(__start___jump_table,
    - __stop___jump_table, start, end);
    + __stop___jump_table, start, end, init);

    if (ret)
    return ret;
    --
    2.30.2


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