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Subject[PATCH v5 1/5] block: add ioprio_check_cap function
Date
From: Adam Manzanares <adam.manzanares@wdc.com>

Aio per command iopriority support introduces a second interface between
userland and the kernel capable of passing iopriority. The aio interface also
needs the ability to verify that the submitting context has sufficient
priviledges to submit IOPRIO_RT commands. This patch creates the
ioprio_check_cap function to be used by the ioprio_set system call and also by
the aio interface.

Signed-off-by: Adam Manzanares <adam.manzanares@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
block/ioprio.c | 22 ++++++++++++++++------
include/linux/ioprio.h | 2 ++
2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/block/ioprio.c b/block/ioprio.c
index 6f5d0b6625e3..f9821080c92c 100644
--- a/block/ioprio.c
+++ b/block/ioprio.c
@@ -61,15 +61,10 @@ int set_task_ioprio(struct task_struct *task, int ioprio)
}
EXPORT_SYMBOL_GPL(set_task_ioprio);

-SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
+int ioprio_check_cap(int ioprio)
{
int class = IOPRIO_PRIO_CLASS(ioprio);
int data = IOPRIO_PRIO_DATA(ioprio);
- struct task_struct *p, *g;
- struct user_struct *user;
- struct pid *pgrp;
- kuid_t uid;
- int ret;

switch (class) {
case IOPRIO_CLASS_RT:
@@ -92,6 +87,21 @@ SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
return -EINVAL;
}

+ return 0;
+}
+
+SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
+{
+ struct task_struct *p, *g;
+ struct user_struct *user;
+ struct pid *pgrp;
+ kuid_t uid;
+ int ret;
+
+ ret = ioprio_check_cap(ioprio);
+ if (ret)
+ return ret;
+
ret = -ESRCH;
rcu_read_lock();
switch (which) {
diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
index 627efac73e6d..4a28cec49ec3 100644
--- a/include/linux/ioprio.h
+++ b/include/linux/ioprio.h
@@ -77,4 +77,6 @@ extern int ioprio_best(unsigned short aprio, unsigned short bprio);

extern int set_task_ioprio(struct task_struct *task, int ioprio);

+extern int ioprio_check_cap(int ioprio);
+
#endif
--
2.15.1
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