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Date: Wed, 31 Mar 2021 23:36:28 -0500 From: ebiederm@...ssion.com (Eric W. Biederman) To: Josh Hunt <johunt@...mai.com> Cc: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, <linux-kernel@...r.kernel.org> Subject: Re: [PATCH] psi: allow unprivileged users with CAP_SYS_RESOURCE to write psi files Josh Hunt <johunt@...mai.com> writes: > Currently only root can write files under /proc/pressure. Relax this to > allow tasks running as unprivileged users with CAP_SYS_RESOURCE to be > able to write to these files. The test for CAP_SYS_RESOURCE really needs to be in open rather than in write. Otherwise a suid root executable could have stdout redirected into these files. Eric > Signed-off-by: Josh Hunt <johunt@...mai.com> > --- > kernel/sched/psi.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c > index b1b00e9bd7ed..98ff7baf1ba8 100644 > --- a/kernel/sched/psi.c > +++ b/kernel/sched/psi.c > @@ -1270,6 +1270,9 @@ static ssize_t psi_write(struct file *file, const char __user *user_buf, > if (!nbytes) > return -EINVAL; > > + if (!capable(CAP_SYS_RESOURCE)) > + return -EPERM; > + > buf_size = min(nbytes, sizeof(buf)); > if (copy_from_user(buf, user_buf, buf_size)) > return -EFAULT; > @@ -1353,9 +1356,9 @@ static int __init psi_proc_init(void) > { > if (psi_enable) { > proc_mkdir("pressure", NULL); > - proc_create("pressure/io", 0, NULL, &psi_io_proc_ops); > - proc_create("pressure/memory", 0, NULL, &psi_memory_proc_ops); > - proc_create("pressure/cpu", 0, NULL, &psi_cpu_proc_ops); > + proc_create("pressure/io", 0666, NULL, &psi_io_proc_ops); > + proc_create("pressure/memory", 0666, NULL, &psi_memory_proc_ops); > + proc_create("pressure/cpu", 0666, NULL, &psi_cpu_proc_ops); > } > return 0; > }
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