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authorJohn Stultz <john.stultz@linaro.org>2016-10-07 17:02:33 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-10-07 18:46:30 -0700
commit4b2bd5fec007a4fd3fc82474b9199af25013de4c (patch)
tree6cd4e88c476f3b7940df7e09e01c0a5355c2c886
parent904763e1fb5eebf8249ec41a2019e5e32246df2f (diff)
proc: fix timerslack_ns CAP_SYS_NICE check when adjusting self
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 privileges 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 Link: http://lkml.kernel.org/r/1471906870-28624-1-git-send-email-john.stultz@linaro.org Signed-off-by: John Stultz <john.stultz@linaro.org> Acked-by: 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: Android Kernel Team <kernel-team@android.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/proc/base.c34
1 files changed, 19 insertions, 15 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index ebccdc192830..dc7fe5f3a53c 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2280,15 +2280,17 @@ 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);
@@ -2314,14 +2316,16 @@ 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);