4.17-stable review patch. If anyone has any objections, please let me know.
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From: Jann Horn jannh@google.com
commit a0341fc1981a950c1e902ab901e98f60e0e243f3 upstream.
This read handler had a lot of custom logic and wrote outside the bounds of the provided buffer. This could lead to kernel and userspace memory corruption. Just use simple_read_from_buffer() with a stack buffer.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Jann Horn jannh@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/misc/ibmasm/ibmasmfs.c | 27 +++------------------------ 1 file changed, 3 insertions(+), 24 deletions(-)
--- a/drivers/misc/ibmasm/ibmasmfs.c +++ b/drivers/misc/ibmasm/ibmasmfs.c @@ -507,35 +507,14 @@ static int remote_settings_file_close(st static ssize_t remote_settings_file_read(struct file *file, char __user *buf, size_t count, loff_t *offset) { void __iomem *address = (void __iomem *)file->private_data; - unsigned char *page; - int retval; int len = 0; unsigned int value; - - if (*offset < 0) - return -EINVAL; - if (count == 0 || count > 1024) - return 0; - if (*offset != 0) - return 0; - - page = (unsigned char *)__get_free_page(GFP_KERNEL); - if (!page) - return -ENOMEM; + char lbuf[20];
value = readl(address); - len = sprintf(page, "%d\n", value); - - if (copy_to_user(buf, page, len)) { - retval = -EFAULT; - goto exit; - } - *offset += len; - retval = len; + len = snprintf(lbuf, sizeof(lbuf), "%d\n", value);
-exit: - free_page((unsigned long)page); - return retval; + return simple_read_from_buffer(buf, count, offset, lbuf, len); }
static ssize_t remote_settings_file_write(struct file *file, const char __user *ubuff, size_t count, loff_t *offset)