Re: GPF in keyring_destroy

[David Howells]

Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:

> > Does the attached patch fix it for you?
> 
> Yes, it fixes the crash for me.

I have an additional patch to prevent keyrings from being constructed by
request_key() at all (though it can still search for them).  Could you give
this a spin in addition to the previous one also?

Thanks,
David
---
commit 27874345bb8d2c39f3d493607a86ecbfcb100405
Author: David Howells <dhowells@xxxxxxxxxx>
Date:   Mon Oct 19 11:20:28 2015 +0100

    KEYS: Don't permit request_key() to construct a new keyring
    
    If request_key() is used to find a keyring, only do the search part - don't
    do the construction part if the keyring was not found by the search.  We
    don't really want keyrings in the negative instantiated state since the
    rejected/negative instantiation error value in the payload is unioned with
    keyring metadata.
    
    Signed-off-by: David Howells <dhowells@xxxxxxxxxx>

diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index 486ef6fa393b..0d6253124278 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -440,6 +440,9 @@ static struct key *construct_key_and_link(struct keyring_search_context *ctx,
 
 	kenter("");
 
+	if (ctx->index_key.type == &key_type_keyring)
+		return ERR_PTR(-EPERM);
+	
 	user = key_user_lookup(current_fsuid());
 	if (!user)
 		return ERR_PTR(-ENOMEM);
--
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