| Message ID | 1471906870-28624-1-git-send-email-john.stultz@linaro.org |
|---|---|
| State | New |
| Headers | show |
On Mon, Aug 22, 2016 at 4:01 PM, John Stultz <john.stultz@linaro.org> wrote: > In changing from checking ptrace_may_access(p, PTRACE_MODE_ATTACH_FSCREDS) > to capable(CAP_SYS_NICE), I missed that ptrace_my_access succeeds > when p == current, but the CAP_SYS_NICE doesn't. > > Thus while the previous commit was intended to loosen the needed > privledges to modify a processes timerslack, it needlessly restricted > a task modifying its own timerslack via the proc/<tid>/timerslack_ns > (which is permitted also via the PR_SET_TIMERSLACK method). > > This patch corrects this by checking if p == current before checking > the CAP_SYS_NICE value. > > This patch applies on top of my two previous patches currently in -mm Ping? Any feedback or comments on this one? thanks -john
On Tue, Aug 30, 2016 at 4:06 PM, Andrew Morton <akpm@linux-foundation.org> wrote: > On Tue, 30 Aug 2016 18:46:23 -0400 Kees Cook <keescook@chromium.org> wrote: > >> On Mon, Aug 22, 2016 at 7:01 PM, John Stultz <john.stultz@linaro.org> wrote: >> > In changing from checking ptrace_may_access(p, PTRACE_MODE_ATTACH_FSCREDS) >> > to capable(CAP_SYS_NICE), I missed that ptrace_my_access succeeds >> > when p == current, but the CAP_SYS_NICE doesn't. >> > >> > Thus while the previous commit was intended to loosen the needed >> > privledges to modify a processes timerslack, it needlessly restricted >> > a task modifying its own timerslack via the proc/<tid>/timerslack_ns >> > (which is permitted also via the PR_SET_TIMERSLACK method). >> > >> > This patch corrects this by checking if p == current before checking >> > the CAP_SYS_NICE value. >> > >> > This patch applies on top of my two previous patches currently in -mm >> > >> > Cc: Kees Cook <keescook@chromium.org> >> > Cc: "Serge E. Hallyn" <serge@hallyn.com> >> > Cc: Andrew Morton <akpm@linux-foundation.org> >> > 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: Android Kernel Team <kernel-team@android.com> >> > Acked-by: Kees Cook <keescook@chromium.org> >> > Signed-off-by: John Stultz <john.stultz@linaro.org> >> >> Andrew, can you take this for v4.8? > > Well, it fixes > proc-relax-proc-tid-timerslack_ns-capability-requirements.patch, > somewhat. And it textually depends on that. > > Do we want all of > > proc-relax-proc-tid-timerslack_ns-capability-requirements.patch > proc-add-lsm-hook-checks-to-proc-tid-timerslack_ns.patch > proc-fix-timerslack_ns-cap_sys_nice-check-when-adjusting-self.patch > > in 4.8? If so, why? No.. they're fine to wait for the 4.9 merge window. But you picking up this last fix is appreciated! thanks -john
diff --git a/fs/proc/base.c b/fs/proc/base.c index 02f8389..01c3c2d 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2281,15 +2281,17 @@ static ssize_t timerslack_ns_write(struct file *file, const char __user *buf, if (!p) return -ESRCH; - if (!capable(CAP_SYS_NICE)) { - count = -EPERM; - goto out; - } + if (p != current) { + if (!capable(CAP_SYS_NICE)) { + count = -EPERM; + goto out; + } - err = security_task_setscheduler(p); - if (err) { - count = err; - goto out; + err = security_task_setscheduler(p); + if (err) { + count = err; + goto out; + } } task_lock(p); @@ -2315,14 +2317,16 @@ static int timerslack_ns_show(struct seq_file *m, void *v) if (!p) return -ESRCH; - if (!capable(CAP_SYS_NICE)) { - err = -EPERM; - goto out; - } + if (p != current) { - err = security_task_getscheduler(p); - if (err) - goto out; + if (!capable(CAP_SYS_NICE)) { + err = -EPERM; + goto out; + } + err = security_task_getscheduler(p); + if (err) + goto out; + } task_lock(p); seq_printf(m, "%llu\n", p->timer_slack_ns);