2019-08-11 23:56:01

by Gustavo A. R. Silva

Subject: [PATCH][next] ima: ima_modsig: Fix use-after-free bug in ima_read_modsig

hdr is being freed and then dereferenced by accessing hdr->pkcs7_msg

Fix this by copying the value returned by PTR_ERR(hdr->pkcs7_msg) into
automatic variable err for its safe use after freeing hdr.

Addresses-Coverity-ID: 1485813 ("Read from pointer after free")
Fixes: 39b07096364a ("ima: Implement support for module-style appended signatures")
Signed-off-by: Gustavo A. R. Silva <[email protected]>
---
security/integrity/ima/ima_modsig.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/security/integrity/ima/ima_modsig.c b/security/integrity/ima/ima_modsig.c
index c412e31d1714..e681d4326145 100644
--- a/security/integrity/ima/ima_modsig.c
+++ b/security/integrity/ima/ima_modsig.c
@@ -91,8 +91,9 @@ int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len,

hdr->pkcs7_msg = pkcs7_parse_message(buf + buf_len, sig_len);
if (IS_ERR(hdr->pkcs7_msg)) {
+ int err = PTR_ERR(hdr->pkcs7_msg);
kfree(hdr);
- return PTR_ERR(hdr->pkcs7_msg);
+ return err;
}

memcpy(hdr->raw_pkcs7, buf + buf_len, sig_len);
--
2.22.0

2019-08-28 13:51:42

by Mimi Zohar

Subject: Re: [PATCH][next] ima: ima_modsig: Fix use-after-free bug in ima_read_modsig

Hi Gustavo,

On Sun, 2019-08-11 at 18:55 -0500, Gustavo A. R. Silva wrote:
> hdr is being freed and then dereferenced by accessing hdr->pkcs7_msg
>
> Fix this by copying the value returned by PTR_ERR(hdr->pkcs7_msg) into
> automatic variable err for its safe use after freeing hdr.
>
> Addresses-Coverity-ID: 1485813 ("Read from pointer after free")
> Fixes: 39b07096364a ("ima: Implement support for module-style appended signatures")
> Signed-off-by: Gustavo A. R. Silva <[email protected]>

This bug was reported Julia and addressed by Thiago on 8/7. If you
would like to add your Review/Tested-by, the patch can be found in the
linux-integrity next-queued-testing branch.

thanks,

Mimi

2019-08-28 18:57:27

by Gustavo A. R. Silva

Subject: Re: [PATCH][next] ima: ima_modsig: Fix use-after-free bug in ima_read_modsig

On 8/28/19 8:50 AM, Mimi Zohar wrote:
> Hi Gustavo,
>
> On Sun, 2019-08-11 at 18:55 -0500, Gustavo A. R. Silva wrote:
>> hdr is being freed and then dereferenced by accessing hdr->pkcs7_msg
>>
>> Fix this by copying the value returned by PTR_ERR(hdr->pkcs7_msg) into
>> automatic variable err for its safe use after freeing hdr.
>>
>> Addresses-Coverity-ID: 1485813 ("Read from pointer after free")
>> Fixes: 39b07096364a ("ima: Implement support for module-style appended signatures")
>> Signed-off-by: Gustavo A. R. Silva <[email protected]>
>
> This bug was reported Julia and addressed by Thiago on 8/7. If you
> would like to add your Review/Tested-by, the patch can be found in the
> linux-integrity next-queued-testing branch.
>

I'm glad this is fixed now. :)

Yeah, you can add my:

Reviewed-by: Gustavo A. R. Silva <[email protected]>

Thanks
--
Gustavo