| Message ID | 20211210182058.43417-1-dave@stgolabs.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | block: fix ioprio_get(IOPRIO_WHO_PGRP) vs setuid(2) | expand |
On Fri, 10 Dec 2021 10:20:58 -0800, Davidlohr Bueso wrote: > do_each_pid_thread(PIDTYPE_PGID) can race with a concurrent > change_pid(PIDTYPE_PGID) that can move the task from one hlist > to another while iterating. Serialize ioprio_get to take > the tasklist_lock in this case, just like it's set counterpart. > > Applied, thanks! [1/1] block: fix ioprio_get(IOPRIO_WHO_PGRP) vs setuid(2) commit: e6a59aac8a8713f335a37d762db0dbe80e7f6d38 Best regards,
diff --git a/block/ioprio.c b/block/ioprio.c index 313c14a70bbd..6f01d35a5145 100644 --- a/block/ioprio.c +++ b/block/ioprio.c @@ -220,6 +220,7 @@ SYSCALL_DEFINE2(ioprio_get, int, which, int, who) pgrp = task_pgrp(current); else pgrp = find_vpid(who); + read_lock(&tasklist_lock); do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { tmpio = get_task_ioprio(p); if (tmpio < 0) @@ -229,6 +230,8 @@ SYSCALL_DEFINE2(ioprio_get, int, which, int, who) else ret = ioprio_best(ret, tmpio); } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); + read_unlock(&tasklist_lock); + break; case IOPRIO_WHO_USER: uid = make_kuid(current_user_ns(), who);
do_each_pid_thread(PIDTYPE_PGID) can race with a concurrent change_pid(PIDTYPE_PGID) that can move the task from one hlist to another while iterating. Serialize ioprio_get to take the tasklist_lock in this case, just like it's set counterpart. Fixes: d69b78ba1de (ioprio: grab rcu_read_lock in sys_ioprio_{set,get}()) Acked-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Davidlohr Bueso <dbueso@suse.de> --- This is basically a resend of https://lore.kernel.org/all/20200817003148.23691-3-dave@stgolabs.net/ with Oleg's ack and without the ioprio_set part as this was fixed later after this patch was lost for whatever reason. block/ioprio.c | 3 +++ 1 file changed, 3 insertions(+)