From: Masami Hiramatsu <mhiramat@kernel.org>
To: Punit Agrawal <punitagrawal@gmail.com>
Cc: naveen.n.rao@linux.ibm.com, anil.s.keshavamurthy@intel.com,
davem@davemloft.net, linux-kernel@vger.kernel.org,
guoren@kernel.org, linux-csky@vger.kernel.org
Subject: Re: [PATCH 1/5] kprobes: Do not use local variable when creating debugfs file
Date: Wed, 9 Jun 2021 23:35:43 +0900 [thread overview]
Message-ID: <20210609233543.e846251ccaa227317de26b11@kernel.org> (raw)
In-Reply-To: <20210609105019.3626677-2-punitagrawal@gmail.com>
On Wed, 9 Jun 2021 19:50:15 +0900
Punit Agrawal <punitagrawal@gmail.com> wrote:
> debugfs_create_file() takes a pointer argument that can be used during
> file operation callbacks (accessible via i_private in the inode
> structure). An obvious requirement is for the pointer to refer to
> valid memory when used.
>
> When creating the debugfs file to dynamically enable / disable
> kprobes, a pointer to local variable is passed to
> debugfs_create_file(); which will go out of scope when the init
> function returns. The reason this hasn't triggered random memory
> corruption is because the pointer is not accessed during the debugfs
> file callbacks.
>
> Fix the incorrect (and unnecessary) usage of local variable during
> debugfs_file_create() by passing NULL instead.
>
Good catch! Since the enabled state is managed by the kprobes_all_disabled
global variable, it is not needed.
Fixes: bf8f6e5b3e51 ("Kprobes: The ON/OFF knob thru debugfs")
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Thank you!
> Signed-off-by: Punit Agrawal <punitagrawal@gmail.com>
> ---
> kernel/kprobes.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 745f08fdd7a6..fdb1ea2e963b 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -2816,13 +2816,12 @@ static const struct file_operations fops_kp = {
> static int __init debugfs_kprobe_init(void)
> {
> struct dentry *dir;
> - unsigned int value = 1;
>
> dir = debugfs_create_dir("kprobes", NULL);
>
> debugfs_create_file("list", 0400, dir, NULL, &kprobes_fops);
>
> - debugfs_create_file("enabled", 0600, dir, &value, &fops_kp);
> + debugfs_create_file("enabled", 0600, dir, NULL, &fops_kp);
>
> debugfs_create_file("blacklist", 0400, dir, NULL,
> &kprobe_blacklist_fops);
> --
> 2.30.2
>
--
Masami Hiramatsu <mhiramat@kernel.org>
next prev parent reply other threads:[~2021-06-09 14:35 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-09 10:50 [PATCH 0/5] kprobes: Bugfix and improvements Punit Agrawal
2021-06-09 10:50 ` [PATCH 1/5] kprobes: Do not use local variable when creating debugfs file Punit Agrawal
2021-06-09 14:35 ` Masami Hiramatsu [this message]
2021-06-10 23:31 ` Punit Agrawal
2021-06-09 10:50 ` [RFC PATCH 2/5] kprobes: Use helper to parse boolean input from userspace Punit Agrawal
2021-06-09 14:37 ` Masami Hiramatsu
2021-06-09 10:50 ` [RFC PATCH 3/5] kprobe: Simplify prepare_kprobe() by dropping redundant version Punit Agrawal
2021-06-09 14:42 ` Masami Hiramatsu
2021-06-09 10:50 ` [RFC PATCH 4/5] csky: ftrace: Drop duplicate implementation of arch_check_ftrace_location() Punit Agrawal
2021-06-09 12:33 ` Guo Ren
2021-06-09 14:29 ` Masami Hiramatsu
2021-06-09 15:47 ` Guo Ren
2021-06-10 0:07 ` Masami Hiramatsu
2021-06-09 10:50 ` [RFC PATCH 5/5] kprobes: Make arch_check_ftrace_location static Punit Agrawal
2021-06-10 0:37 ` Masami Hiramatsu
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