Messages in this thread Patch in this message | | | From | John Stultz <> | Subject | [PATCH] proc: Fix timerslack_ns CAP_SYS_NICE check when adjusting self | Date | Tue, 9 Aug 2016 16:54:17 -0700 |
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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> Signed-off-by: John Stultz <john.stultz@linaro.org> --- fs/proc/base.c | 34 +++++++++++++++++++--------------- 1 file changed, 19 insertions(+), 15 deletions(-)
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); -- 1.9.1
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