| Message ID | 20231220015106.16732-3-warthog618@gmail.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | gpiolib: cdev: guard tidying | expand |
On Wed, Dec 20, 2023 at 10:53:07PM +0800, Kent Gibson wrote: > On Wed, Dec 20, 2023 at 04:30:24PM +0200, Andy Shevchenko wrote: > > On Wed, Dec 20, 2023 at 09:51:04AM +0800, Kent Gibson wrote: > > > The size of struct linereq may exceed a page, so allocate space for > > > it using kvzalloc() instead of kzalloc(). > > > > It might be this needs a bit of elaboration. The kmalloc() tries to allocate > > a contiguous (in physical address space) chunk of memory and with fragmented > > memory it might be not possible. So the above issue might (rarely) happen. > > In most cases the call to kmalloc() will succeed. > > For sure, the kzalloc() generally works - or we wouldn't've gotten this > far as tests with MAX_LINES would've been failing. > We are targetting a very niche failure mode here. > > The size allocated can only be determined at runtime, may be more or > less than a page, and we don't care whether the physical memory allocated > is contiguous. > As such kvzalloc() is the appropriate allocator. > > Are you suggesting repeating the relevant sections of the > kmalloc/vmalloc() documentation or Memory Allocation Guide as part of the > checkin comment? I suggesting to make clear in the commit message that: - there is no bug per se with the code logic (i.o.w. there is no issue to have allocations bigger than one page) - this is very rarely case when it might be a problem You can also put a reference to the documentation, if you wish. This should be harmless and adding not more than a line into the commit message (or even as a Link: tag to the HTML variant of it).
diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c index 44d864f63130..6fec793f5513 100644 --- a/drivers/gpio/gpiolib-cdev.c +++ b/drivers/gpio/gpiolib-cdev.c @@ -1723,7 +1723,7 @@ static void linereq_free(struct linereq *lr) kfifo_free(&lr->events); kfree(lr->label); gpio_device_put(lr->gdev); - kfree(lr); + kvfree(lr); } static int linereq_release(struct inode *inode, struct file *file) @@ -1788,7 +1788,7 @@ static int linereq_create(struct gpio_device *gdev, void __user *ip) if (ret) return ret; - lr = kzalloc(struct_size(lr, lines, ulr.num_lines), GFP_KERNEL); + lr = kvzalloc(struct_size(lr, lines, ulr.num_lines), GFP_KERNEL); if (!lr) return -ENOMEM; lr->num_lines = ulr.num_lines;
The size of struct linereq may exceed a page, so allocate space for it using kvzalloc() instead of kzalloc(). Signed-off-by: Kent Gibson <warthog618@gmail.com> --- drivers/gpio/gpiolib-cdev.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)