From: Peter Zijlstra <peterz@infradead.org>
To: Wang Hai <wanghai38@huawei.com>
Cc: jpoimboe@redhat.com, jbaron@akamai.com, rostedt@goodmis.org,
ardb@kernel.org, mingo@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] static_call: fix null-ptr-deref in static_call_del_module
Date: Sat, 9 Oct 2021 12:00:37 +0200 [thread overview]
Message-ID: <20211009100037.GU174703@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20211009074428.1668662-1-wanghai38@huawei.com>
On Sat, Oct 09, 2021 at 03:44:28PM +0800, Wang Hai wrote:
> I got a NULL pointer dereference report when doing fault injection test:
>
> BUG: kernel NULL pointer dereference, address: 0000000000000009
> ...
> RIP: 0010:static_call_del_module+0x7a/0x100
> ...
> Call Trace:
> static_call_module_notify+0x1e1/0x200
> notifier_call_chain_robust+0x6f/0xe0
> blocking_notifier_call_chain_robust+0x4e/0x70
> load_module+0x21f7/0x2b60
> __do_sys_finit_module+0xb0/0xf0
> ? __do_sys_finit_module+0xb0/0xf0
> __x64_sys_finit_module+0x1a/0x20
> do_syscall_64+0x34/0xb0
> entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> When loading a module, if it fails to allocate memory for static
> calls, it will delete the non-existent mods (mods == 1) in the
> static_call_module_notify()'s error path.
>
> static_call_module_notify
> static_call_add_module
> __static_call_init
> site_mod = kzalloc() // fault injection
> static_call_del_module // access non-existent mods
>
> This patch fixes the bug by skipping the operation when the key
> has no mods.
>
> Fixes: a945c8345ec0 ("static_call: Allow early init")
> Signed-off-by: Wang Hai <wanghai38@huawei.com>
> ---
> kernel/static_call.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/static_call.c b/kernel/static_call.c
> index 43ba0b1e0edb..c3f8ffc5a52f 100644
> --- a/kernel/static_call.c
> +++ b/kernel/static_call.c
> @@ -400,7 +400,7 @@ static void static_call_del_module(struct module *mod)
>
> for (site = start; site < stop; site++) {
> key = static_call_key(site);
> - if (key == prev_key)
> + if (key == prev_key || !static_call_key_has_mods(key))
> continue;
>
> prev_key = key;
Should you not update prev_key in that case? Also have you looked at
jump_label_del_module() which is very similar in construction?
next prev parent reply other threads:[~2021-10-09 10:01 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-09 7:44 [PATCH] static_call: fix null-ptr-deref in static_call_del_module Wang Hai
2021-10-09 10:00 ` Peter Zijlstra [this message]
2021-10-11 3:18 ` wanghai (M)
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