[PATCH] block: grant IOPRIO_CLASS_RT to CAP_SYS_NICE

From: Khazhismel Kumykov <khazhy@google.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: Serge Hallyn <serge@hallyn.com>,
	Paolo Valente <paolo.valente@linaro.org>,
	Bart Van Assche <bvanassche@acm.org>,
	linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	Khazhismel Kumykov <khazhy@google.com>
Subject: [PATCH] block: grant IOPRIO_CLASS_RT to CAP_SYS_NICE
Date: Mon, 24 Aug 2020 13:45:01 -0700	[thread overview]
Message-ID: <20200824204501.1707957-1-khazhy@google.com> (raw)

CAP_SYS_ADMIN is too broad, and ionice fits into CAP_SYS_NICE's grouping.

Retain CAP_SYS_ADMIN permission for backwards compatibility.

Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
---
 block/ioprio.c                  | 2 +-
 include/uapi/linux/capability.h | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/block/ioprio.c b/block/ioprio.c
index 77bcab11dce5..4572456430f9 100644
--- a/block/ioprio.c
+++ b/block/ioprio.c
@@ -69,7 +69,7 @@ int ioprio_check_cap(int ioprio)
 
 	switch (class) {
 		case IOPRIO_CLASS_RT:
-			if (!capable(CAP_SYS_ADMIN))
+			if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_NICE))
 				return -EPERM;
 			/* fall through */
 			/* rt has prio field too */
diff --git a/include/uapi/linux/capability.h b/include/uapi/linux/capability.h
index 395dd0df8d08..c6ca33034147 100644
--- a/include/uapi/linux/capability.h
+++ b/include/uapi/linux/capability.h
@@ -288,6 +288,8 @@ struct vfs_ns_cap_data {
    processes and setting the scheduling algorithm used by another
    process. */
 /* Allow setting cpu affinity on other processes */
+/* Allow setting realtime ioprio class */
+/* Allow setting ioprio class on other processes */
 
 #define CAP_SYS_NICE         23
 
-- 
2.28.0.297.g1956fa8f8d-goog

