The patch titled
Subject: proc: fix timerslack_ns CAP_SYS_NICE check when adjusting self
has been added to the -mm tree. Its filename is
proc-fix-timerslack_ns-cap_sys_nice-check-when-adjusting-self.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/proc-fix-timerslack_ns-cap_sys_nice-check-when-adjusting-self.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/proc-fix-timerslack_ns-cap_sys_nice-check-when-adjusting-self.patch
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------------------------------------------------------
From: John Stultz <john.stultz@xxxxxxxxxx>
Subject: 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@xxxxxxxxxx
Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: "Serge E. Hallyn" <serge@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Cc: Oren Laadan <orenl@xxxxxxxxxxx>
Cc: Ruchi Kandoi <kandoiruchi@xxxxxxxxxx>
Cc: Rom Lemarchand <romlem@xxxxxxxxxxx>
Cc: Todd Kjos <tkjos@xxxxxxxxxx>
Cc: Colin Cross <ccross@xxxxxxxxxxx>
Cc: Nick Kralevich <nnk@xxxxxxxxxx>
Cc: Dmitry Shmidt <dimitrysh@xxxxxxxxxx>
Cc: Elliott Hughes <enh@xxxxxxxxxx>
Cc: Android Kernel Team <kernel-team@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/base.c | 36 ++++++++++++++++++++----------------
1 file changed, 20 insertions(+), 16 deletions(-)
diff -puN fs/proc/base.c~proc-fix-timerslack_ns-cap_sys_nice-check-when-adjusting-self fs/proc/base.c
--- a/fs/proc/base.c~proc-fix-timerslack_ns-cap_sys_nice-check-when-adjusting-self
+++ a/fs/proc/base.c
@@ -2285,15 +2285,17 @@ static ssize_t timerslack_ns_write(struc
if (!p)
return -ESRCH;
- if (!capable(CAP_SYS_NICE)) {
- count = -EPERM;
- goto out;
- }
-
- err = security_task_setscheduler(p);
- if (err) {
- count = err;
- 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;
+ }
}
task_lock(p);
@@ -2319,14 +2321,16 @@ static int timerslack_ns_show(struct seq
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);
_
Patches currently in -mm which might be from john.stultz@xxxxxxxxxx are
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
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