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    Subject[PATCH 5.4 24/70] kprobes: Limit max data_size of the kretprobe instances
    Date
    From: Masami Hiramatsu <mhiramat@kernel.org>

    commit 6bbfa44116689469267f1a6e3d233b52114139d2 upstream.

    The 'kprobe::data_size' is unsigned, thus it can not be negative. But if
    user sets it enough big number (e.g. (size_t)-8), the result of 'data_size
    + sizeof(struct kretprobe_instance)' becomes smaller than sizeof(struct
    kretprobe_instance) or zero. In result, the kretprobe_instance are
    allocated without enough memory, and kretprobe accesses outside of
    allocated memory.

    To avoid this issue, introduce a max limitation of the
    kretprobe::data_size. 4KB per instance should be OK.

    Link: https://lkml.kernel.org/r/163836995040.432120.10322772773821182925.stgit@devnote2

    Cc: stable@vger.kernel.org
    Fixes: f47cd9b553aa ("kprobes: kretprobe user entry-handler")
    Reported-by: zhangyue <zhangyue1@kylinos.cn>
    Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
    Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    include/linux/kprobes.h | 2 ++
    kernel/kprobes.c | 3 +++
    2 files changed, 5 insertions(+)

    --- a/include/linux/kprobes.h
    +++ b/include/linux/kprobes.h
    @@ -155,6 +155,8 @@ struct kretprobe {
    raw_spinlock_t lock;
    };

    +#define KRETPROBE_MAX_DATA_SIZE 4096
    +
    struct kretprobe_instance {
    struct hlist_node hlist;
    struct kretprobe *rp;
    --- a/kernel/kprobes.c
    +++ b/kernel/kprobes.c
    @@ -2003,6 +2003,9 @@ int register_kretprobe(struct kretprobe
    }
    }

    + if (rp->data_size > KRETPROBE_MAX_DATA_SIZE)
    + return -E2BIG;
    +
    rp->kp.pre_handler = pre_handler_kretprobe;
    rp->kp.post_handler = NULL;
    rp->kp.fault_handler = NULL;

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