From: David Miller <davem@davemloft.net>
To: ast@plumgrid.com
Cc: mingo@kernel.org, rostedt@goodmis.org, wangnan0@huawei.com,
hekuang@huawei.com, daniel@iogearbox.net,
brendan.d.gregg@gmail.com, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH net-next] bpf: add support for %s specifier to bpf_trace_printk()
Date: Thu, 27 Aug 2015 15:34:09 -0700 (PDT) [thread overview]
Message-ID: <20150827.153409.893765406170260565.davem@davemloft.net> (raw)
In-Reply-To: <1440656819-25622-1-git-send-email-ast@plumgrid.com>
From: Alexei Starovoitov <ast@plumgrid.com>
Date: Wed, 26 Aug 2015 23:26:59 -0700
> +/* similar to strncpy_from_user() but with extra checks */
> +static void probe_read_string(char *buf, int size, long unsafe_ptr)
> +{
> + char dst[4];
> + int i = 0;
> +
> + size--;
> + for (;;) {
> + if (probe_kernel_read(dst, (void *) unsafe_ptr, 4))
> + break;
I don't think this does the right thing when the string is not a multiple
of 3 and ends at the last byte of a page that ends a valid region of
kernel memory.
Seeing this kind of error makes me skeptical to the overall value of
optimizing this :-/
next prev parent reply other threads:[~2015-08-27 22:34 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-27 6:26 Alexei Starovoitov
2015-08-27 22:34 ` David Miller [this message]
2015-08-27 23:06 ` Alexei Starovoitov
2015-08-27 23:20 ` David Miller
2015-08-27 23:43 ` Steven Rostedt
2015-08-28 1:58 ` Alexei Starovoitov
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