4.9-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit 8da0b4f692c6d90b09c91f271517db746a22ff67 ]
Access to timerslack_ns is controlled by a process having CAP_SYS_NICE in its effective capability set, but the current check looks in the root namespace instead of the process' user namespace. Since a process is allowed to do other activities controlled by CAP_SYS_NICE inside a namespace, it should also be able to adjust timerslack_ns.
Link: http://lkml.kernel.org/r/20181030180012.232896-1-bmgordon@google.com Signed-off-by: Benjamin Gordon bmgordon@google.com Acked-by: "Eric W. Biederman" ebiederm@xmission.com Cc: John Stultz john.stultz@linaro.org Cc: "Eric W. Biederman" ebiederm@xmission.com Cc: Kees Cook keescook@chromium.org Cc: "Serge E. Hallyn" serge@hallyn.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Arjan van de Ven arjan@linux.intel.com Cc: Oren Laadan orenl@cellrox.com Cc: Ruchi Kandoi kandoiruchi@google.com Cc: Rom Lemarchand romlem@android.com Cc: Todd Kjos tkjos@google.com Cc: Colin Cross ccross@android.com Cc: Nick Kralevich nnk@google.com Cc: Dmitry Shmidt dimitrysh@google.com Cc: Elliott Hughes enh@google.com Cc: Alexey Dobriyan adobriyan@gmail.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/proc/base.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c index 79702d405ba7..f73de326c630 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2337,10 +2337,13 @@ static ssize_t timerslack_ns_write(struct file *file, const char __user *buf, return -ESRCH;
if (p != current) { - if (!capable(CAP_SYS_NICE)) { + rcu_read_lock(); + if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) { + rcu_read_unlock(); count = -EPERM; goto out; } + rcu_read_unlock();
err = security_task_setscheduler(p); if (err) { @@ -2373,11 +2376,14 @@ static int timerslack_ns_show(struct seq_file *m, void *v) return -ESRCH;
if (p != current) { - - if (!capable(CAP_SYS_NICE)) { + rcu_read_lock(); + if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) { + rcu_read_unlock(); err = -EPERM; goto out; } + rcu_read_unlock(); + err = security_task_getscheduler(p); if (err) goto out;