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[73.67.244.238]) by smtp.gmail.com with ESMTPSA id ra13sm7540521pac.29.2016.08.02.17.54.24 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 02 Aug 2016 17:54:25 -0700 (PDT) From: John Stultz To: lkml Cc: John Stultz , Kees Cook , "Serge E. Hallyn" , Andrew Morton , Thomas Gleixner , Arjan van de Ven , Oren Laadan , Ruchi Kandoi , Rom Lemarchand , Todd Kjos , Colin Cross , Nick Kralevich , Dmitry Shmidt , Elliott Hughes , Android Kernel Team Subject: [RFC][PATCH] proc: Fix timerslack_ns CAP_SYS_NICE check when adjusting self Date: Tue, 2 Aug 2016 17:54:21 -0700 Message-Id: <1470185661-15655-1-git-send-email-john.stultz@linaro.org> X-Mailer: git-send-email 1.9.1 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//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 Cc: "Serge E. Hallyn" Cc: Andrew Morton Cc: Thomas Gleixner CC: Arjan van de Ven Cc: Oren Laadan Cc: Ruchi Kandoi Cc: Rom Lemarchand Cc: Todd Kjos Cc: Colin Cross Cc: Nick Kralevich Cc: Dmitry Shmidt Cc: Elliott Hughes Cc: Android Kernel Team Signed-off-by: John Stultz --- fs/proc/base.c | 34 +++++++++++++++++++--------------- 1 file changed, 19 insertions(+), 15 deletions(-) -- 1.9.1 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);