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gpiolib: Fix line event handling in syscall compatible mode 

The introduced line event handling ABI in the commit

  61f922db72 ("gpio: userspace ABI for reading GPIO line events")

missed the fact that 64-bit kernel may serve for 32-bit applications.
In such case the very first check in the lineevent_read() will fail
due to alignment differences.

To workaround this introduce lineevent_get_size() helper which returns actual
size of the structure in user space.

Fixes: 61f922db72 ("gpio: userspace ABI for reading GPIO line events")
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
This commit is contained in:
Andy Shevchenko 2020-09-15 15:58:16 +03:00 committed by Bartosz Golaszewski
parent 1b02d9e770
commit 5ad284ab3a
1 changed files with 30 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

34
drivers/gpio/gpiolib-cdev.c
View File

@ -423,6 +423,21 @@ static __poll_t lineevent_poll(struct file *file,
return events;
}
static ssize_t lineevent_get_size(void)
{
#ifdef __x86_64__
/* i386 has no padding after 'id' */
if (in_ia32_syscall()) {
struct compat_gpioeevent_data {
compat_u64 timestamp;
u32 id;
};
return sizeof(struct compat_gpioeevent_data);
}
#endif
return sizeof(struct gpioevent_data);
}
static ssize_t lineevent_read(struct file *file,
char __user *buf,
@ -432,9 +447,20 @@ static ssize_t lineevent_read(struct file *file,
struct lineevent_state *le = file->private_data;
struct gpioevent_data ge;
ssize_t bytes_read = 0;
ssize_t ge_size;
int ret;
if (count < sizeof(ge))
/*
* When compatible system call is being used the struct gpioevent_data,
* in case of at least ia32, has different size due to the alignment
* differences. Because we have first member 64 bits followed by one of
* 32 bits there is no gap between them. The only difference is the
* padding at the end of the data structure. Hence, we calculate the
* actual sizeof() and pass this as an argument to copy_to_user() to
* drop unneeded bytes from the output.
*/
ge_size = lineevent_get_size();
if (count < ge_size)
return -EINVAL;
do {
@ -470,10 +496,10 @@ static ssize_t lineevent_read(struct file *file,
break;
}
if (copy_to_user(buf + bytes_read, &ge, sizeof(ge)))
if (copy_to_user(buf + bytes_read, &ge, ge_size))
return -EFAULT;
bytes_read += sizeof(ge);
} while (count >= bytes_read + sizeof(ge));
bytes_read += ge_size;
} while (count >= bytes_read + ge_size);
return bytes_read;
}