Re: [PATCH v4 1/3] block: add ioprio_check_cap function

[Christoph Hellwig]

On Thu, May 17, 2018 at 01:38:01PM -0700, adam.manzana...@wdc.com wrote:
> From: Adam Manzanares 
> 
> 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 

Looks fine,

Reviewed-by: Christoph Hellwig 

[PATCH v4 1/3] block: add ioprio_check_cap function

[adam . manzanares]

From: Adam Manzanares 

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 
---
 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