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Subject[PATCH 11/18] staging: gasket: always allow root open for write
Date
From: Todd Poynor <toddpoynor@google.com>

Always allow root to open device for writing.

Drop special-casing of ioctl permissions for root vs. owner.

Reported-by: Dmitry Torokhov <dtor@chromium.org>
Signed-off-by: Zhongze Hu <frankhu@chromium.org>
Signed-off-by: Todd Poynor <toddpoynor@google.com>
---
drivers/staging/gasket/apex_driver.c | 9 +++------
drivers/staging/gasket/gasket_core.c | 8 +++++---
drivers/staging/gasket/gasket_ioctl.c | 15 ++++++---------
3 files changed, 14 insertions(+), 18 deletions(-)

diff --git a/drivers/staging/gasket/apex_driver.c b/drivers/staging/gasket/apex_driver.c
index b1318482ba65..ffe11d8168ea 100644
--- a/drivers/staging/gasket/apex_driver.c
+++ b/drivers/staging/gasket/apex_driver.c
@@ -644,13 +644,10 @@ static bool is_gcb_in_reset(struct gasket_dev *gasket_dev)
static uint apex_ioctl_check_permissions(struct file *filp, uint cmd)
{
struct gasket_dev *gasket_dev = filp->private_data;
- int root = capable(CAP_SYS_ADMIN);
- int is_owner = gasket_dev->dev_info.ownership.is_owned &&
- current->tgid == gasket_dev->dev_info.ownership.owner;
+ fmode_t write;

- if (root || is_owner)
- return 1;
- return 0;
+ write = filp->f_mode & FMODE_WRITE;
+ return write;
}

/*
diff --git a/drivers/staging/gasket/gasket_core.c b/drivers/staging/gasket/gasket_core.c
index 0c45c54254fb..5908964f0039 100644
--- a/drivers/staging/gasket/gasket_core.c
+++ b/drivers/staging/gasket/gasket_core.c
@@ -1101,6 +1101,7 @@ static int gasket_open(struct inode *inode, struct file *filp)
char task_name[TASK_COMM_LEN];
struct gasket_cdev_info *dev_info =
container_of(inode->i_cdev, struct gasket_cdev_info, cdev);
+ int is_root = capable(CAP_SYS_ADMIN);

gasket_dev = dev_info->gasket_dev_ptr;
driver_desc = gasket_dev->internal_desc->driver_desc;
@@ -1114,7 +1115,7 @@ static int gasket_open(struct inode *inode, struct file *filp)
"Attempting to open with tgid %u (%s) (f_mode: 0%03o, "
"fmode_write: %d is_root: %u)",
current->tgid, task_name, filp->f_mode,
- (filp->f_mode & FMODE_WRITE), capable(CAP_SYS_ADMIN));
+ (filp->f_mode & FMODE_WRITE), is_root);

/* Always allow non-writing accesses. */
if (!(filp->f_mode & FMODE_WRITE)) {
@@ -1128,8 +1129,9 @@ static int gasket_open(struct inode *inode, struct file *filp)
gasket_dev, "Current owner open count (owning tgid %u): %d.",
ownership->owner, ownership->write_open_count);

- /* Opening a node owned by another TGID is an error (even root.) */
- if (ownership->is_owned && ownership->owner != current->tgid) {
+ /* Opening a node owned by another TGID is an error (unless root) */
+ if (ownership->is_owned && ownership->owner != current->tgid &&
+ !is_root) {
gasket_log_error(
gasket_dev,
"Process %u is opening a node held by %u.",
diff --git a/drivers/staging/gasket/gasket_ioctl.c b/drivers/staging/gasket/gasket_ioctl.c
index 4758083fb19b..23875fd465f6 100644
--- a/drivers/staging/gasket/gasket_ioctl.c
+++ b/drivers/staging/gasket/gasket_ioctl.c
@@ -180,7 +180,7 @@ long gasket_is_supported_ioctl(uint cmd)
*/
static uint gasket_ioctl_check_permissions(struct file *filp, uint cmd)
{
- uint alive, root, device_owner;
+ uint alive;
fmode_t read, write;
struct gasket_dev *gasket_dev = (struct gasket_dev *)filp->private_data;

@@ -191,33 +191,30 @@ static uint gasket_ioctl_check_permissions(struct file *filp, uint cmd)
alive, gasket_dev->status);
}

- root = capable(CAP_SYS_ADMIN);
read = filp->f_mode & FMODE_READ;
write = filp->f_mode & FMODE_WRITE;
- device_owner = (gasket_dev->dev_info.ownership.is_owned &&
- current->tgid == gasket_dev->dev_info.ownership.owner);

switch (cmd) {
case GASKET_IOCTL_RESET:
case GASKET_IOCTL_CLEAR_INTERRUPT_COUNTS:
- return root || (write && device_owner);
+ return write;

case GASKET_IOCTL_PAGE_TABLE_SIZE:
case GASKET_IOCTL_SIMPLE_PAGE_TABLE_SIZE:
case GASKET_IOCTL_NUMBER_PAGE_TABLES:
- return root || read;
+ return read;

case GASKET_IOCTL_PARTITION_PAGE_TABLE:
case GASKET_IOCTL_CONFIG_COHERENT_ALLOCATOR:
- return alive && (root || (write && device_owner));
+ return alive && write;

case GASKET_IOCTL_MAP_BUFFER:
case GASKET_IOCTL_UNMAP_BUFFER:
- return alive && (root || (write && device_owner));
+ return alive && write;

case GASKET_IOCTL_CLEAR_EVENTFD:
case GASKET_IOCTL_SET_EVENTFD:
- return alive && (root || (write && device_owner));
+ return alive && write;
}

return 0; /* unknown permissions */
--
2.18.0.203.gfac676dfb9-goog
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