2022-04-07 13:42:24

by baihaowen

Subject: [PATCH] libbpf: potential NULL dereference in usdt_manager_attach_usdt()

link could be null but still dereference bpf_link__destroy(&link->link)
and it will lead to a null pointer access.

Signed-off-by: Haowen Bai <[email protected]>
---
tools/lib/bpf/usdt.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/lib/bpf/usdt.c b/tools/lib/bpf/usdt.c
index 1bce2eab5e89..b02ebc4ba57c 100644
--- a/tools/lib/bpf/usdt.c
+++ b/tools/lib/bpf/usdt.c
@@ -996,7 +996,7 @@ struct bpf_link *usdt_manager_attach_usdt(struct usdt_manager *man, const struct
link = calloc(1, sizeof(*link));
if (!link) {
err = -ENOMEM;
- goto err_out;
+ goto link_err;
}

link->usdt_man = man;
@@ -1072,7 +1072,7 @@ struct bpf_link *usdt_manager_attach_usdt(struct usdt_manager *man, const struct

err_out:
bpf_link__destroy(&link->link);
-
+link_err:
free(targets);
hashmap__free(specs_hash);
if (elf)
--
2.7.4

2022-04-07 20:04:42

by patchwork-bot+netdevbpf

Subject: Re: [PATCH] libbpf: potential NULL dereference in usdt_manager_attach_usdt()

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko <[email protected]>:

On Thu, 7 Apr 2022 10:38:17 +0800 you wrote:
> link could be null but still dereference bpf_link__destroy(&link->link)
> and it will lead to a null pointer access.
>
> Signed-off-by: Haowen Bai <[email protected]>
> ---
> tools/lib/bpf/usdt.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)

Here is the summary with links:
- libbpf: potential NULL dereference in usdt_manager_attach_usdt()
https://git.kernel.org/bpf/bpf-next/c/e58c5c971746

You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

2022-04-07 20:35:06

by Andrii Nakryiko

Subject: Re: [PATCH] libbpf: potential NULL dereference in usdt_manager_attach_usdt()

On Wed, Apr 6, 2022 at 7:38 PM Haowen Bai <[email protected]> wrote:
>
> link could be null but still dereference bpf_link__destroy(&link->link)
> and it will lead to a null pointer access.
>
> Signed-off-by: Haowen Bai <[email protected]>
> ---
> tools/lib/bpf/usdt.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tools/lib/bpf/usdt.c b/tools/lib/bpf/usdt.c
> index 1bce2eab5e89..b02ebc4ba57c 100644
> --- a/tools/lib/bpf/usdt.c
> +++ b/tools/lib/bpf/usdt.c
> @@ -996,7 +996,7 @@ struct bpf_link *usdt_manager_attach_usdt(struct usdt_manager *man, const struct
> link = calloc(1, sizeof(*link));
> if (!link) {
> err = -ENOMEM;
> - goto err_out;
> + goto link_err;

this is not a complete fix because there are two more similar goto
err_out; above which you didn't fix. I think better fix is to just add
if (link) check before bpf_link__destroy(), which is what I did
locally when applying.


> }
>
> link->usdt_man = man;
> @@ -1072,7 +1072,7 @@ struct bpf_link *usdt_manager_attach_usdt(struct usdt_manager *man, const struct
>
> err_out:
> bpf_link__destroy(&link->link);
> -
> +link_err:
> free(targets);
> hashmap__free(specs_hash);
> if (elf)
> --
> 2.7.4
>

2022-04-08 01:58:32

by baihaowen

Subject: Re: [PATCH] libbpf: potential NULL dereference in usdt_manager_attach_usdt()

在 4/8/22 3:04 AM, Andrii Nakryiko 写道:
> On Wed, Apr 6, 2022 at 7:38 PM Haowen Bai <[email protected]> wrote:
>> link could be null but still dereference bpf_link__destroy(&link->link)
>> and it will lead to a null pointer access.
>>
>> Signed-off-by: Haowen Bai <[email protected]>
>> ---
>> tools/lib/bpf/usdt.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/lib/bpf/usdt.c b/tools/lib/bpf/usdt.c
>> index 1bce2eab5e89..b02ebc4ba57c 100644
>> --- a/tools/lib/bpf/usdt.c
>> +++ b/tools/lib/bpf/usdt.c
>> @@ -996,7 +996,7 @@ struct bpf_link *usdt_manager_attach_usdt(struct usdt_manager *man, const struct
>> link = calloc(1, sizeof(*link));
>> if (!link) {
>> err = -ENOMEM;
>> - goto err_out;
>> + goto link_err;
> this is not a complete fix because there are two more similar goto
> err_out; above which you didn't fix. I think better fix is to just add
> if (link) check before bpf_link__destroy(), which is what I did
> locally when applying.
>
>
>> }
>>
>> link->usdt_man = man;
>> @@ -1072,7 +1072,7 @@ struct bpf_link *usdt_manager_attach_usdt(struct usdt_manager *man, const struct
>>
>> err_out:
>> bpf_link__destroy(&link->link);
>> -
>> +link_err:
>> free(targets);
>> hashmap__free(specs_hash);
>> if (elf)
>> --
>> 2.7.4
>>
Thank you for your kindness help. :)

--
Haowen Bai