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SubjectRe: [PATCH] kprobes: fix out-of-bounds in register_kretprobe
On Wed,  1 Dec 2021 13:48:55 +0800
zhangyue <zhangyue1@kylinos.cn> wrote:

> When the data 'rp->data_size' is negative, the code
> 'sizeof(struct kretprobe_instance)+rp->data_size'
> is less than 'sizeof(struct kretprobe_instance)'
>
> At this time, the pointer 'inst' may be out of
> bound when it is in use.

Good catch! but in that case register_kretprobe() should return -EINVAL
since there is no reason to allow minus data_size. (Thus, it must be
unsigned int, and limit with some maximum size.)

Let me fix that.

Thank you,

>
> Signed-off-by: zhangyue <zhangyue1@kylinos.cn>
> ---
> kernel/kprobes.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 1cf8bca1ea86..71cf6bde299f 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1983,7 +1983,7 @@ int kprobe_on_func_entry(kprobe_opcode_t *addr, const char *sym, unsigned long o
> int register_kretprobe(struct kretprobe *rp)
> {
> int ret;
> - struct kretprobe_instance *inst;
> + struct kretprobe_instance *inst = NULL;
> int i;
> void *addr;
>
> @@ -2024,7 +2024,8 @@ int register_kretprobe(struct kretprobe *rp)
>
> rp->rph->rp = rp;
> for (i = 0; i < rp->maxactive; i++) {
> - inst = kzalloc(sizeof(struct kretprobe_instance) +
> + if (rp->data_size >= 0)
> + inst = kzalloc(sizeof(struct kretprobe_instance) +
> rp->data_size, GFP_KERNEL);
> if (inst == NULL) {
> refcount_set(&rp->rph->ref, i);
> --
> 2.30.0
>


--
Masami Hiramatsu <mhiramat@kernel.org>

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