Hi Christian,
On Wed, 2021-04-14 at 13:50 +0200, Christian Brauner wrote:
> Hey,
>
> [Resending since the previous mail somehow hasn't made it onto the list.]
>
> While working on a patch to port ecryptfs to use clone_private_mount() I
> hit the splat in [1] with v5.12-rc6 (Without any of my changes.). To
> reproduce this you can use the config in [5]. Then run the scripts [2]
> and [3] in two terminals. The kernel command line was [4]:
>
> while true; do ./test.sh; done
> while true; do ./test2.sh; done
>
> and wait for [1] to appear.
>
> The two test scripts aren't specifically designed to trigger this issue.
> They were stress tests for my ecryptfs clone_private_mount() port. They
> just allow to trigger this issue.
>
> From a very uninformed position it seemed that:
>
> void integrity_inode_free(struct inode *inode)
> {
> struct integrity_iint_cache *iint;
>
> if (!IS_IMA(inode))
> return;
Thank you for all the details.
A builtin IMA policy wasn't specified on the boot command line. Unless
a custom IMA policy is loaded, it shouldn't get beyond this
point. Before looking any farther, I would appreciate your confirming
that you've loaded a custom IMA policy. To see if a policy has been
loaded, cat /sys/kernel/security/ima/policy.
thanks,
Mimi
>
> write_lock(&integrity_iint_lock);
> iint = __integrity_iint_find(inode);
> ^^^^^
> >>>>>>> is somehow NULL?
>
> rb_erase(&iint->rb_node, &integrity_iint_tree);
> write_unlock(&integrity_iint_lock);
>
> iint_free(iint);
> }
>
> So I've placed a BUG_ON() in there:
>
> diff --git a/security/integrity/iint.c b/security/integrity/iint.c
> index 0ba01847e836..d5152b5ef517 100644
> --- a/security/integrity/iint.c
> +++ b/security/integrity/iint.c
> @@ -152,6 +152,7 @@ void integrity_inode_free(struct inode *inode)
>
> write_lock(&integrity_iint_lock);
> iint = __integrity_iint_find(inode);
> + BUG_ON(!iint);
> rb_erase(&iint->rb_node, &integrity_iint_tree);
> write_unlock(&integrity_iint_lock);
>
> and indeed, I get:
>
> [ 266.308227] ------------[ cut here ]------------
> [ 266.308592] kernel BUG at security/integrity/iint.c:155!
> [ 266.312120] invalid opcode: 0000 [#1] PREEMPT SMP KASAN
> [ 266.313898] CPU: 0 PID: 5867 Comm: rm Tainted: G E 5.12.0-rc6-clone-private-mount-8a97af3f33b5 #380
> [ 266.317651] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009)/LXD, BIOS 0.0.0 02/06/2015
