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SubjectRe: [PATCH] x86/mce: Avoid using object after free in genpool.
On Wed, Mar 23, 2016 at 09:14:40AM -0700, Tony Luck wrote:
> When we loop over all queued machine check error records to pass
> them to the registered notifiers we use llist_for_each_entry().
> But the loop calls gen_pool_free() for the entry in the body of
> the loop - and then the iterator looks at node->next after the
> free.
>
> Use llist_for_each_entry_safe() instead.
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Tony Luck <tony.luck@intel.com>
> ---
> arch/x86/kernel/cpu/mcheck/mce-genpool.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/mcheck/mce-genpool.c b/arch/x86/kernel/cpu/mcheck/mce-genpool.c
> index 0a850100c594..2658e2af74ec 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce-genpool.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce-genpool.c
> @@ -29,7 +29,7 @@ static char gen_pool_buf[MCE_POOLSZ];
> void mce_gen_pool_process(void)
> {
> struct llist_node *head;
> - struct mce_evt_llist *node;
> + struct mce_evt_llist *node, *tmp;
> struct mce *mce;
>
> head = llist_del_all(&mce_event_llist);
> @@ -37,7 +37,7 @@ void mce_gen_pool_process(void)
> return;
>
> head = llist_reverse_order(head);
> - llist_for_each_entry(node, head, llnode) {
> + llist_for_each_entry_safe(node, tmp, head, llnode) {
> mce = &node->mce;
> atomic_notifier_call_chain(&x86_mce_decoder_chain, 0, mce);
> gen_pool_free(mce_evt_pool, (unsigned long)node, sizeof(*node));
> --

Acked-by: Borislav Petkov <bp@suse.de>

I have a couple more RAS patches for tip, want me to pick that one up
too? I'm going to send my pile to tip guys after -rc1 is out.

--
Regards/Gruss,
Boris.

ECO tip #101: Trim your mails when you reply.

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