Greg Kroah-Hartman gregkh@linuxfoundation.org writes:
4.20-stable review patch. If anyone has any objections, please let me know.
No objection. But I think of this as a feature addition rather than a fix for something. As a feature that we now allow something we previously did not does this qualify for a backport to stable?
It is probably no more harmful in this instance than adding PCI IDs to a driver. So I am not worried. I am curious the current guidelines are.
In most cases a small relaxation of permissions like this requires a lot of bug fixing as typically code protected by capable(CAP_XXX) has been written and tested assuming a trusted root user. Those bug fixes are many times too large for a stable backport.
Eric
[ 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 ce3465479447..98525af0953e 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2356,10 +2356,13 @@ 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) { @@ -2392,11 +2395,14 @@ 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;