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block: Fix sys_ioprio_set(.which=IOPRIO_WHO_PGRP) task iteration

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do_each_pid_thread() { } while_each_pid_thread() is a double loop and
thus break doesn't work as expected. Also, it should be used under
tasklist_lock because otherwise we can race against change_pid() for
PGID/SID.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/YG7Q5C4Rb5dx5GFx@hirez.programming.kicks-ass.net
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Peter Zijlstra 2021-04-08 11:46:12 +02:00 committed by Jens Axboe
parent 3212135a71
commit 40c7fd3fdf
1 changed files with 9 additions and 2 deletions
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11
block/ioprio.c
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@ -119,11 +119,17 @@ SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
pgrp = task_pgrp(current); pgrp = task_pgrp(current);
else else
pgrp = find_vpid(who); pgrp = find_vpid(who);
read_lock(&tasklist_lock);
do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
ret = set_task_ioprio(p, ioprio); ret = set_task_ioprio(p, ioprio);
if (ret) if (ret) {
break; read_unlock(&tasklist_lock);
goto out;
}
} while_each_pid_thread(pgrp, PIDTYPE_PGID, p); } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
read_unlock(&tasklist_lock);
break; break;
case IOPRIO_WHO_USER: case IOPRIO_WHO_USER:
uid = make_kuid(current_user_ns(), who); uid = make_kuid(current_user_ns(), who);
@ -153,6 +159,7 @@ free_uid:
ret = -EINVAL; ret = -EINVAL;
} }
out:
rcu_read_unlock(); rcu_read_unlock();
return ret; return ret;
} }