Re: [PATCH v2] integrity: Fix possible multiple allocation in integrity_inode_get()

[Jarkko Sakkinen]

On Thu Jun 1, 2023 at 9:42 AM EEST, Tianjia Zhang wrote:
> When integrity_inode_get() is querying and inserting the cache, there
> is a conditional race in the concurrent environment.
>
> The race condition is the result of not properly implementing
> "double-checked locking". In this case, it first checks to see if the
> iint cache record exists before taking the lock, but doesn't check
> again after taking the integrity_iint_lock.
>
> Fixes: bf2276d10ce5 ("ima: allocating iint improvements")
> Signed-off-by: Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx>
> Cc: Dmitry Kasatkin <dmitry.kasatkin@xxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx> # v3.10+

s/v3.10/v4.14/

I.e. cover only currently maintained longterms, right?


> ---
>  security/integrity/iint.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/security/integrity/iint.c b/security/integrity/iint.c
> index c73858e8c6d5..a462df827de2 100644
> --- a/security/integrity/iint.c
> +++ b/security/integrity/iint.c
> @@ -43,12 +43,10 @@ static struct integrity_iint_cache *__integrity_iint_find(struct inode *inode)
>  		else if (inode > iint->inode)
>  			n = n->rb_right;
>  		else
> -			break;
> +			return iint;
>  	}
> -	if (!n)
> -		return NULL;
>  
> -	return iint;
> +	return NULL;
>  }
>  
>  /*
> @@ -113,10 +111,15 @@ struct integrity_iint_cache *integrity_inode_get(struct inode *inode)
>  		parent = *p;
>  		test_iint = rb_entry(parent, struct integrity_iint_cache,
>  				     rb_node);
> -		if (inode < test_iint->inode)
> +		if (inode < test_iint->inode) {
>  			p = &(*p)->rb_left;
> -		else
> +		} else if (inode > test_iint->inode) {
>  			p = &(*p)->rb_right;
> +		} else {
> +			write_unlock(&integrity_iint_lock);
> +			kmem_cache_free(iint_cache, iint);
> +			return test_iint;
> +		}
>  	}
>  
>  	iint->inode = inode;
> -- 
> 2.24.3 (Apple Git-128)

Mimi, are you picking this?

Off-topic: how do you compile kernel on macOS, you're using VM right?
I'm just interested because I recently bought Mac mini for both
compiling and testing arm64. Optimal would be to be able to compile
the kernel on bare metal and then deploy to a VM...


BR, Jarkko