linux-kernel - [PATCH v2] block: grant IOPRIO_CLASS_RT to CAP_SYS

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Message-Id: <20200824221034.2170308-1-khazhy@google.com>
Date:   Mon, 24 Aug 2020 15:10:34 -0700
From:   Khazhismel Kumykov <khazhy@...gle.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Serge Hallyn <serge@...lyn.com>,
        Paolo Valente <paolo.valente@...aro.org>,
        Bart Van Assche <bvanassche@....org>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Khazhismel Kumykov <khazhy@...gle.com>
Subject: [PATCH v2] block: grant IOPRIO_CLASS_RT to CAP_SYS_NICE

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@...gle.com>
---
 block/ioprio.c                  | 2 +-
 include/uapi/linux/capability.h | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

v2: fix embarrassing logic mistake
diff --git a/block/ioprio.c b/block/ioprio.c
index 77bcab11dce5..276496246fe9 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_NICE) && !capable(CAP_SYS_ADMIN))
 				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